# Precision Ground Toolroom Stones



## Bob Korves

WOW!  Just wow!


----------



## ddickey

I watched that yesterday at work. Amazing.


----------



## jbolt

Hey Bob, you have a surface grinder. Are you taking orders?


----------



## Bob Korves

jbolt said:


> Hey Bob, you have a surface grinder. Are you taking orders?


Not yet, but I am looking closely at 7" 1A1 diamond grinding wheels, 150 grit, and at the Norton combination stones.  For those who do not use stones for cleaning up burs, it really works well and the original geometry and surface can be kept mostly intact when used correctly.  Robin's methods kick that idea up by several more notches, and I will definitely be going there...


----------



## chips&more

I'm probably going to get slammed! I have a dedicated granite surface plate that I use for such purposes. When it starts to look ugly and or not work as it should, I will go buy another plate. But I have been using the current plate for about 20 years now and it still works great. Yes, I know a surface plate is not a deburring station, but it’s my shop and I have more than one plate…Dave


----------



## jbolt

I have been using very fine hard stones, albeit much smaller, for as long as I remember for the same kind of things Robin was demonstrating. Something I picked up from my mentor many moons ago.

It never occurred to me the stones may not be flat or to use a second stone to keep the surfaces of the stones clean.  

Seriously wish I had room for a surface grinder. Grrrr...

Which stones are you looking at?


----------



## 4GSR

Stones are on order.  Should have them Saturday on my Amazon Prime.  Now, all I have to do is mix up some coolant for the surface grinder and mount my diamond wheel and I'll be ready to go!


----------



## Bob Korves

jbolt said:


> Which stones are you looking at?


I am looking at the same stones Robin was using, Norton 61463685560.  That was the 6 x 2 x 1".
Like this https://www.zoro.com/norton-combina...81&gclid=CPn2_8WxvtQCFQlVfgodQFMFcw&gclsrc=ds
but still looking for a better price.
Robin also showed the same stones in 8 x 2 x 1" and 4 x 1-3/4 x 5/8".


----------



## ddickey

I thought they were $500/pair?


----------



## Bob Korves

ddickey said:


> I thought they were $500/pair?


If you buy them ready to use from me they are.   That is at my $1.00/hr labor rate.   My labor includes procrastination time...


----------



## aliva

Very good video, but in all reality does the average hobby machinist need to get the stones that flat, I think its overkill. yor just removing burs
I recently bought some Japanese water stones for knife sharpening, 200 grit, 4000 grit and 6000 grit. there were around $60:00 each.
I also bought a flattening stone for $50:00 and a cleaning stone for $30:00 does everything  I want and does a darn good job sharpening knives.
I also have a sharpening steel, but it's ceramic at 8000 grit


----------



## jbolt

aliva said:


> Very good video, but in all reality does the average hobby machinist need to get the stones that flat, I think its overkill. yor just removing burs



I'm not sure how many hobby machinists even think about stoning precision surfaces. From the outset it seems like a bad idea ,and could be if you used "any stone". Once you understand that with the correct stone and technique you won't damage the precision surface. Robin did a good job of explaining that in his video.

There are lots a precision mating surfaces that stack up in our work holding that benefit from good machine practices.

I know I have gotten some sideways looks when I take a stone to the spindle nose and back of a chuck or a tool with a tapered shank. As we move around our not-so-hard big clunky chucks and vises or have a bunch of tools with precision ground shanks floating around together in a drawer they get bumped and nicked and need to tuned up occasionally.

I'd bet money I'm not the only person who has drilled a hole too close to a parallel and turned that nice crisp ground edge into a saw tooth. With a proper stone and technique that can be cleaned up without further damaging the parallel.


----------



## Doubleeboy

Did Robin mention in the video what diamond wheel he used on surface grinder?  If he did I missed it.
Thanks!


----------



## Bob Korves

Doubleeboy said:


> Did Robin mention in the video what diamond wheel he used on surface grinder?  If he did I missed it.
> Thanks!


7" O.D., 150 grit, 1-1/4" bore, 1/2" wide, 1/8" thick resin bonded media, 100% concentration.  I just ordered one of that description from Shars, p/n 505-2233.  $81.00 plus freight from Shars, $91.00 and free shipping on eBay.  I went with the eBay order, saved about five bucks.  I also ordered the stones today, Norton 6 x 2 x 1" combination aluminum oxide,  part number 05108568.  $15.99 each.


----------



## ddickey

Every mounting hole I see is for 1-1/4". My grinder takes 3/4"


----------



## chips&more

ddickey said:


> Every mounting hole I see is for 1-1/4". My grinder takes 3/4"


OK, but isn’t it a simple lathe operation to make a bushing reducer. Or, am I missing something? My little Sanford has a 1/2” spindle. All my wheels have 1 1/4” holes. I just made some bushings. And the arbor flange and washer still catch the sides of the wheels. All is good now. Note; make sure you use a paper washer on each side of the wheel when mounting…Dave


----------



## Bob Korves

ddickey said:


> Every mounting hole I see is for 1-1/4". My grinder takes 3/4"


1-1/4" with a 3" spindle taper per foot is a very common size for surface grinder wheel adapters (hubs).  What kind of grinder are you contemplating using?  This project requires an accurate grinder and flat and true chuck, a smooth running and tight spindle without runout, and a wheel with near zero runout (well dressed.)  Not sure yet, but it might require coolant as well.  If you do not have all that, you will not achieve what is needed to make quite flat stones with quite flat abrasive surfaces with a large surface area so they will work correctly.  Make sure you understand what Robin is achieving in the video.  It is incredibly cool, but not easy to achieve.


----------



## woodchucker

ddickey said:


> Every mounting hole I see is for 1-1/4". My grinder takes 3/4"


Got a lathe? Make a bushing.


----------



## silence dogood

This may be a silly question.  Robin rubs his stones back and forth.  Would it not be better to rub them in a figure 8 motion?  I was wondering if that would help keep them flat.


----------



## Bob Korves

silence dogood said:


> This may be a silly question.  Robin rubs his stones back and forth.  Would it not be better to rub them in a figure 8 motion?  I was wondering if that would help keep them flat.


Ask Robin the answer to that as a comment to his video.  He is so far ahead of me that I would not presume to know the answer.  You can bet there is a well considered answer.  Robin does not do things "just because."  Robin is the most talented machinist I have seen yet, not that I am any kind of an expert.  Seriously, ask him, and then report back with what he says...

(I got my two stones yesterday and the diamond wheel for my surface grinder today.  Ready to get started...)


----------



## 4GSR

Bob, I picked up a set of stones made by GWHOLE, made in China.  I was quite impressed on how flat they are right out the box. Not sure about the quality of the stone.  When I rub them together, they seem to wear down producing powdery superfine grit.  I also have a set of Norton stones as Robin uses in his video coming sometime next week.  When I get them, I'll see how flat they are coming out of the box.  Then I'll set up and SG all four stones and report my results.  Ken


----------



## Bob Korves

4gsr said:


> Bob, I picked up a set of stones made by GWHOLE, made in China.  I was quite impressed on how flat they are right out the box. Not sure about the quality of the stone.  When I rub them together, they seem to wear down producing powdery superfine grit.  I also have a set of Norton stones as Robin uses in his video coming sometime next week.  When I get them, I'll see how flat they are coming out of the box.  Then I'll set up and SG all four stones and report my results.  Ken


Thanks, Ken.  I will be trying it, too.  I do not have flood coolant on my surface grinder and I wonder how the diamond grit in the resin bond will do against the stones.  I do have a mister setup I could use, or perhaps a plastic pump bottle like for various household cleaners.  It might be good to find a pump bottle that can send a real stream, I will look around in my stuff for one.  We want to flatten the grains, not tear them out.  Heat could cause problems with the grit coming apart from the bond, or with damaging the resin bond on the wheel.  Wisdom?


----------



## 4GSR

I have a flood coolant system set up but haven't used it yet.  I've been dry grinding since day one.  The only real problem I see using dry grinding on these stones is the dust it will create.  A mister I think will be your best bet keeping the dust down.  I think from our standpoint, we will see very little difference between dry and wet grinding of stones.  As for clogging up the diamond grinding wheel, I don't think that will be a problem.  I don't think using a mister will clog up the grinding wheel either.  Should help keep it from clogging up.  Ken


----------



## 4GSR

As much as I have used diamond wheels to grind carbide, I've never had a problem with the wheel clogging up on a 150 or 220 grit wheel.  Now, the 800 grit wheel I have on the old slow speed grinder for sharpening my scrapers, it seems to load up a little, but a wipe from a rag when it's not running usually all it needs to remove spent grit.  Now, the few Chinese diamond wheels I've bought, I have mixed results in using them.  They don't seem to cut as good as a good old Norton diamond wheel will.  Just my opinion!


----------



## Dabbler

I loved the video and ordered an offshore diamond wheel and 2 - 4" X 1" stones to try out.  I intend to dry grind the stones and see what happens.  They say that I'll get them some time mid-to-late Jul.  Fingers crossed!


----------



## Bob Korves

Dabbler said:


> I loved the video and ordered an offshore diamond wheel and 2 - 4" X 1" stones to try out.  I intend to dry grind the stones and see what happens.  They say that I'll get them some time mid-to-late Jul.  Fingers crossed!


Let's all keep in the loop on this.  I have the diamond wheel and the stones, but it has been blazing hot here (108 F forecast today, 110 F tomorrow)  and I have some other things I need to get done as well.  I am quite interested if dry grinding will work for this.  My plan at this point is to use my mister unit.    I wonder if cutting oil or shortening might work?


----------



## 4GSR

Bob Korves said:


> ..........   I wonder if cutting oil or shortening might work?


I don't think you want to try that on a diamond wheel.

Just as hot here if you figure in the humidity, just have too many irons in the fire here to play right now.  Maybe this weekend before I can play.


----------



## Dabbler

My friend Bert only dry grinds with his diamond wheels.  I know about toxicity of carbide, etc, but from the wheel longevity of the grinding wheel, his have lasted 30 years.


----------



## Bob Korves

Dabbler said:


> My friend Bert only dry grinds with his diamond wheels.  I know about toxicity of carbide, etc, but from the wheel longevity of the grinding wheel, his have lasted 30 years.


Thanks, Dabbler.  I am not in my comfort zone with these resin bond wheels.  I have a 4" cup wheel with resin bond diamonds, 600 grit, and it works good dry, but I only use it at very slow RPM for sharpening carbide scraper blades.  Robin was taking some eye opening plunge cuts in his video, and I don't think I am ready for any of that yet, don't want to destroy the wheel or throw a stone.  Speaking of which, are there other work holding ideas beyond the feather board tools Robin was using?  Is just blocking them in well with steel near the stone thickness good enough?


----------



## Dabbler

Bob Korves said:


> Thanks, Dabbler.  I am not in my comfort zone with these resin bond wheels.  I have a 4" cup wheel with resin bond diamonds, 600 grit, and it works good dry, but I only use it at very slow RPM for sharpening carbide scraper blades.  Robin was taking some eye opening plunge cuts in his video, and I don't think I am ready for any of that yet, don't want to destroy the wheel or throw a stone.  Speaking of which, are there other work holding ideas beyond the feather board tools Robin was using?  Is just blocking them in well with steel near the stone thickness good enough?



I plan to make a  steel fixture for grinding my 4 X 1 stones, consisting of a channel that is wide enough for the stones plus 2 layers of notepad cardboard.  There will be set screws along one side to put even force on the stone and a plate at the end for support.  I'll pregrind the bottom so the stone will be held flat (or on 3 points as necessary).  When I'm done the jig I'll post a photo or 2.

I believe Bert's diamond stones are vitrified bond, I'll check with him on this.  

My diamond stones are coming as resin bond (cheap, less than 20$ CDN each).   I know that you can't put much pressure or generate much heat or the resin is toast.  I'll be plunge cutting as well, but in tenths with very slow hand wheel feeding, and waits at the end of each pass.  I won't be using coolant, even though I have the setup.  I don't intend to clean up 100% of the faces, so if there's a little around the edge not flat, NBD.  I want to get to the end result for this test with as little fuss as possible....  About the jig - for a very experienced grinder hand, I'm sure the finger boards are very safe.  I'm absolute novice to SG, and rely on Bert for my info.  For this test I'm much more comfortable making the jig.  Maybe one day I'll make finger boards and try it.  -- When I've got a lot more miles on the grinder.

I worry if the parts are just blocked in, then there is too little pressure on the stone to keep it from vibrating and moving. just my $.02.


----------



## Bob Korves

Dabbler said:


> I plan to make a  steel fixture for grinding my 4 X 1 stones, consisting of a channel that is wide enough for the stones plus 2 layers of notepad cardboard.  There will be set screws along one side to put even force on the stone and a plate at the end for support.  I'll pregrind the bottom so the stone will be held flat (or on 3 points as necessary).  When I'm done the jig I'll post a photo or 2.
> 
> I believe Bert's diamond stones are vitrified bond, I'll check with him on this.
> 
> My diamond stones are coming as resin bond (cheap, less than 20$ CDN each).   I know that you can't put much pressure or generate much heat or the resin is toast.  I'll be plunge cutting as well, but in tenths with very slow hand wheel feeding, and waits at the end of each pass.  I won't be using coolant, even though I have the setup.  I don't intend to clean up 100% of the faces, so if there's a little around the edge not flat, NBD.  I want to get to the end result for this test with as little fuss as possible....  About the jig - for a very experienced grinder hand, I'm sure the finger boards are very safe.  I'm absolute novice to SG, and rely on Bert for my info.  For this test I'm much more comfortable making the jig.  Maybe one day I'll make finger boards and try it.  -- When I've got a lot more miles on the grinder.
> 
> I worry if the parts are just blocked in, then there is too little pressure on the stone to keep it from vibrating and moving. just my $.02.


Please keep us in the loop on your progress and any additional recommendations and cautions you and Bert come up with.  I really like your fixture idea, and may borrow it.

I re-read the latest comments on Robin's video last night and he used the same Shars 505-2233 resin bond wheel that I purchased.  It is nice to know that it worked for him...


----------



## Dabbler

I noticed he did the edges using his toolmakers vise;  I will try to use my vise instead of a jig, since my stones are only 4" long...


----------



## Bob Korves

Dabbler said:


> I noticed he did the edges using his toolmakers vise;  I will try to use my vise instead of a jig, since my stones are only 4" long...


Yes, I was looking at that, too.  With precision parallels under the free hanging sides, it would probably work just fine, even on my 6" stones.


----------



## tyler machine

So $500 for a set that's ready to use IS out of the question for most people.
What would be a reasonable price?


----------



## Bob Korves

Well, anyone who wants a pair and does not have a good surface grinder and an appropriate diamond wheel is a potential customer.  Making them to the required tolerances is not something that can be done with a cobbled together setup.  The stones alone cost $30+.  Not being a professional, I have little idea of the actual time it would take to make a set and handle the transaction.  More machine time will be needed than most might guess.  There are also a few expendables and some shop overhead costs involved.  The real question becomes what you can make them for and make a reasonable profit, and how large the run might be at that price.  Just my view of it, I have the required stuff and will be making my own.  Perhaps a head count of those who might be interested in a pair of precision stones might give an idea of the tentative interest out there.  Buyer cost is still the important factor in how many would be interested.


----------



## Dabbler

I'm also making myself a pair of mini stones.   I don't expect my first try to be right in any way.  After spending the time to learn how to do it effectively I could then predict what it would be worth to make up the stones.  Not that I'm in the business of manufacturing anything, but some kind of small incentive is needed to take me away from my projects!

It would be only right to know how much the diamond wheel is worn out by making each pair - at 80$+ US, I hope the wear isn't too excessive. (Name brand stones are 3 times the price, but may last longer).

I've already planned to make some sets as gifts for a couple of friends that have done me favours in the last year.  I'm hoping that short run will give me the experience to determine a fair price for someone who doesn't have  a good SG setup.


----------



## tyler machine

I still have some testing to do, but I'm looking at offering these in different sizes and shapes.

I can do the 6 X 2 X 1 , 8 X 2 X 1 and the slip stone shape.

I'm also going to try a set of smaller stones. 1/2 X 1/2 X 4 and 1/2 triangle X 4.

Wondering if offering them on Ebay would be a good start.


----------



## Bob Korves

tyler machine said:


> I still have some testing to do, but I'm looking at offering these in different sizes and shapes.
> 
> I can do the 6 X 2 X 1 , 8 X 2 X 1 and the slip stone shape.
> 
> I'm also going to try a set of smaller stones. 1/2 X 1/2 X 4 and 1/2 triangle X 4.
> 
> Wondering if offering them on Ebay would be a good start.


The smaller ones sound like a good idea.


----------



## Dresden

Usually a granite rubbing block is used to detect burrs, when I worked we ground a stone on the surface grinder with the regular wheel.


----------



## thayne_1

If you decide to market this I would be interested in a pair


----------



## countryguy

ddickey said:


> I thought they were $500/pair?


This site has the $500 pair.  I did not find anything reasonable for a price I can consider affording. 
http://www.airbearings.com/flatstones


For $20...
Like this https://www.zoro.com/norton-combina...81&gclid=CPn2_8WxvtQCFQlVfgodQFMFcw&gclsrc=ds

For the $7 and up range.. Some Amazon sorted low to high
https://tinyurl.com/y9vq8rn3

Here is the Amazon list w/ just Norton selected;
*https://tinyurl.com/yayv8uey*

I am going to put a few on order myself.  This is a fun thread!!! Thanks all.


----------



## Bob Korves

countryguy said:


> This site has the $500 pair.  I did not find anything reasonable for a price I can consider affording.
> http://www.airbearings.com/flatstones
> 
> 
> For $20...
> Like this https://www.zoro.com/norton-combina...81&gclid=CPn2_8WxvtQCFQlVfgodQFMFcw&gclsrc=ds
> 
> For the $7 and up range.. Some Amazon sorted low to high
> https://tinyurl.com/y9vq8rn3
> 
> Here is the Amazon list w/ just Norton selected;
> *https://tinyurl.com/yayv8uey*
> 
> I am going to put a few on order myself.  This is a fun thread!!! Thanks all.


Got mine from MSC for about $16 each, and got the diamond wheel from Shars on eBay for $91 shipped.


----------



## tyler machine

I would be interested to know what the quality is like of the $4 stones. 
If the abrasive and bonding are comparable to Norton, then it shouldn't matter using the cheaper stones.

Has anybody had any experience with the cheaper stuff?


----------



## Bob Korves

tyler machine said:


> I would be interested to know what the quality is like of the $4 stones.
> If the abrasive and bonding are comparable to Norton, then it shouldn't matter using the cheaper stones.
> 
> Has anybody had any experience with the cheaper stuff?


I am one of the most frugal guys you might ever meet, but after paying $91 for the diamond wheel, and the amount of work and time that will be involved with this project, it just does not make sense to me to cheap out by a few dollars on the stones themselves, which will be rubbing on our expen$ive tooling and machines.


----------



## Dabbler

I decided to try this on the 'cheap-cheap', just to see what happens:  A 20$ CDN diamond wheel, and two 4$ CDN stones.  I'll post pictures -if- they ever arrive.


----------



## Bob Korves

Dabbler said:


> I decided to try this on the 'cheap-cheap', just to see what happens:  A 20$ CDN diamond wheel, and two 4$ CDN stones.  I'll post pictures -if- they ever arrive.


I am interested in how it turns out.  Great prices...


----------



## tyler machine

I'm interested in how people are truing up their diamond wheels.


----------



## Bob Korves

tyler machine said:


> I'm interested in how people are truing up their diamond wheels.


Me, too, though I have not even mounted and checked it yet...


----------



## Dabbler

So Here's what Bert tells me:  You don't need to balance or true a diamond wheel, because they are *supposed* to be concentric and since the greater mass is in the aluminum which has very uniform density, the only problem would be the arbor hole. The diamond wheel will eventually wear truer with time, but if it is slightly 'bumping' due to a high spot, you just grind slower until the grind is more uniform.

High quality name brand stones are always (except in very rare cases) concentric, finished and balanced.  When you mount a diamond wheel, it will usually seat with in a half thou of centre.  This is good enough to get started until it wears true.

- share with us your experiences when you get started!


----------



## Joe in Oz

I got my diamond AUS$30 wheel the other day too. Will mount it in the surface grinder to see how good it is.
This one is a resin bonded wheel, so it should be able to be dressed slightly with a coarse stone.
I'll get a couple of india stones tomorrow.


----------



## Rex Walters

Like everyone else in this thread, I'm fascinated by the video. 

I'll trust anything Robin has to say absolutely -- the man's a wizard. 

But why was a diamond wheel in a surface grinder the only method that worked for him to make them? He didn't report what other methods he attempted, but the first that comes to my mind is lapping on a diamond plate like this one (it's how I used to flatten water stones for sharpening woodworking tools).

How flat do they have to be to work the way he shows in the video?

I'm very curious to see how flat you're able to get your stones. Please take the time after you grind them to measure them on a surface plate with a tenths indicator (use a gauge block on top to eliminate the surface roughness).

I'm curious to see how flat I can get a stone by lapping it on my diamond plate (not sure how flat my diamond plate is, but I'll check that first). If the diamond plate isn't flat enough, I'll follow up with sandpaper on a granite surface plate. If that doesn't work for some reason, I might try some coarse carborundum grinding grit on a temporary lap (just a piece of cast iron durabar that's been scraped flat -- not my box parallel!). (Somewhere I acquired several film tubes with different grits.)

If I have time, I'll try some experiments tomorrow. I'll report back how far I get without a surface grinder. I think I've got a couple stones I can experiment with.


----------



## Rex Walters

Uh oh. I just rewatched the video and he explicitly mentioned that lapping didn't work. 

I'm not exactly optimistic, but I'll still see how flat I can get them.


----------



## Bob Korves

Rex, I have some ceramic stones and a few years ago I made one dead flat on a DMT diamond plate.  It works great for many things, but does not appear to be in the same league as what Robin is doing.  The ceramic stone is very fine, and it was flattened in the same interest of making a better stone for removing burs on hardened steel tooling.  It does not leave visible scratches on the surface of the metal, but is also very slow to remove metal to repair the burs.  Perhaps doing the same to a coarser stone would give a better result.  Seeing the obvious complete success of Robin's work, I am inclined to follow his lead faithfully, and have purchased the diamond wheel and stones to do it.  The man knows what he is doing...


----------



## Rex Walters

Yup, since Robin said it can't be done any other way I'm not optimistic. I don't own a surface grinder, though, so figure it can't hurt to experiment.

For my next trick I'm going to climb in the ring and fight Floyd Mayweather. 

I initially thought he was just getting them flat, but I now think the diamond wheel must do something to the surface of the stone. If anyone finds a link to the (U Penn?) paper he mentioned I'd be interested to read it.

I'm an engineer by training and inclination: if I can't measure something it doesn't exist! I just want something objective to measure to see what I'm after. Even if I had a surface grinder, I don't trust my skill enough to take a resulting stone to anything important without measuring or testing it somehow.

I don't appear to have any small India stones, though. Just slipstones, ceramic stones, and water stones. I'll order a couple before performing any experiments.

I also saw in the comments that he mentions using 3um to 6um diamond slurry to lap -- that's *way* finer than I expected (equivalent to P3000 to P6000 Grit lapping paper). I do have some lapping films that fine, but I don't think I'll be able to bring myself to use them with an India stone!

I'd have thought the pores of the stone were bigger than 3um!

His comments indicate he may be offering some for sale soon. I'll probably just get in on that. 
-- 
Rex


----------



## tyler machine

I would think that the grit would be carried by the stone instead of the cast iron because of the porous surface of the stone. I could be totally wrong 
but I would think you'd be cutting more cast iron than stone with the abrasive. Interested to see what you get.
I did try to check the stones I flattened. The best I can tell, I'm well within .001 It's hard to get a good reading because of the porous surface. I tried using a ceramic gauge block to bridge the peaks of the surface.


----------



## Rex Walters

One of the commenters (that Robin agreed with) said the diamond wheel actually shears/grinds the individual grit particles in the stone. If that's true then I can see how only high speed grinding would suffice.

I find that ... surprising ... though.


----------



## Rex Walters

tyler machine said:


> I tried using a ceramic gauge block to bridge the peaks of the surface.



Put the stone on your surface plate and a 1-2-3 block or other precision ground part like a gage block or small parallel on top of the stone at each end, then indicate off the top of that. This will average out any surface irregularity in the stone.

Robin is almost certainly getting his stones within 0.0001" across the 6" length of his stone. (The man knows precision.)

Regards,
-- 
Rex


----------



## tyler machine

Using a 1-2-3 block would just show overall parallelism. What you're after is and even distribution of bearing points. With enough bearing points being in contact with the surface no one point can generate enough force to cut. 

Also I used slip stones to make my first sets.


----------



## Rex Walters

tyler machine said:


> Using a 1-2-3 block would just show overall parallelism. What you're after is and even distribution of bearing points.



While I'm no expert, I do know a little about handscraping and testing your progress.

You can either attempt to measure each individual high spot (bearing point) on your stone directly, measuring each individual peak and valley, or you can rest a precise thickness part on top of the peaks and measure from that.

I'd suggest the later may be easier, is definitely the recommended practice, and will likely lead to more repeatable results.

I think your point is that the top surface of your stone can be flat but not parallel to the bottom surface. This is certainly true, but you can use the averaging of a gage block to map out the topology regardless. Just move the gage block to various locations and measure from there. A 1-2-3 block is a little big, but will still give you meaningful results if you move it to each end and the middle and take readings at each location. A small jo block would be better.

If you get a deviation of 0.001" at one end vs the other, and the middle doesn't show a deviation of close to 0.0005" then your part definitely isn't flat.

Regards,
--
Rex


----------



## Bob Korves

The genius to the method that Robin is using is that it actually grinds the individual grains of the stone's abrasive dead flat and parallel.  The result of that is that the grains cannot cut anything that is not sticking up above the surface that is being rubbed against.  Any amount of imperfection in the stone's flatness will cause problems with the goal of cutting nothing but the high spots.  Also, the reason it does not cut the flat surface of the work is both the flattened grains and their large area of contact, which together does not allow any cutting.  Any imperfections of the stone surface, like scallops, wheel hop, or whatever else, even tiny, will degrade the results.  That's how I see it, anyway, and that is what I understand from Robin's video.  There are definitely ways to improve the surface by tweaking whatever method of grinding that is used, but it will not take much imperfection to ruin the results, at least the results Robin is getting, which is extraordinary!


----------



## ddickey

Looks like a new channel.


----------



## Cactus Farmer

I have a Rockwell T&C grinder that will do surface work too. I look for abused stones that are sometimes swaybacked to the max. I use a diamond wheel (I have several) to make the surface flat again. A little water mist coolant is in order as there is some heat generated. They appear to my gunsmith eye flat as a flitter (technical term) . Even hard Arkansas stones can be saved from the sad state of abuse they have suffered.


----------



## benmychree

I wonder what effect that the heat generated by the grinding has on the flatness of the stones; I know that with grinding steel parallels dry that it is near impossible to keep them (parallel) and straight, at least on the parallels that I made about 50 years ago of 0-1 tool steel, hardened; the heat of the cut would bow them up in the middle, even with the magnetic chuck on full power.  Originally, I did not worry about exact nominal size, just parallelism; this was on a grinder 16 X 72" and not in good alignment, so I thought it might be nice to grind them to nominal size, but my B&S Micromaster does not currently have coolant and the results were not so good.  I do not know how much effect that the lightening holes had and how much different a solid parallel would act but assume that it would make a difference.  So, with stones ground dry, how flat is flat?


----------



## Rex Walters

Dresden said:


> Usually a granite rubbing block is used to detect burrs



Chips&More (Dave)'s comment earlier in the thread and yours puzzled me until I started reading about gage block stones.

Starrett still sells stones expressly for removing burrs from *gage blocks*, which is simply amazing to me. See page 408 of their current catalog:




The cheapest of them (for steel) appears to just be a small piece of granite that is precision ground. For ceramic or carbide they recommend their aluminum oxide stones (the larger one has serrations which apparently helps with the "feel" per Starrett). The granite stone is what has my attention, though.

I think Dave may have it exactly right. The cheapest option for a "precision ground stone" may be simply a small, cheap granite surface plate. 

I'd be willing to bet that rubbing a hardened and ground part on a surface plate would burnish and identify high spots identically to what you see in Robin's video.

Anyone here ever used any of those Starrett stones?
-- 
Rex


----------



## tyler machine

Just a flat granite block will define and burnish the high spots but it won't shear them off or improve the surface like a flattened aluminum oxide stone.


----------



## maker of things

Heard about Robin's channel while watching Tom Lipton.  I hope he makes a LOT more videos.


----------



## Bob Korves

Rex Walters said:


> The cheapest option for a "precision ground stone" may be simply a small, cheap granite surface plate.


That could be difficult to take to the work, depending on size, shape, and location.  I also agree with Jon that it would only burnish, not remove burs.


----------



## chips&more

Rex Walters said:


> Chips&More (Dave)'s comment earlier in the thread and yours puzzled me until I started reading about gage block stones.
> 
> Starrett still sells stones expressly for removing burrs from *gage blocks*, which is simply amazing to me. See page 408 of their current catalog:
> 
> View attachment 237871
> 
> 
> The cheapest of them (for steel) appears to just be a small piece of granite that is precision ground. For ceramic or carbide they recommend their aluminum oxide stones (the larger one has serrations which apparently helps with the "feel" per Starrett). The granite stone is what has my attention, though.
> 
> I think Dave may have it exactly right. The cheapest option for a "precision ground stone" may be simply a small, cheap granite surface plate.
> 
> I'd be willing to bet that rubbing a hardened and ground part on a surface plate would burnish and identify high spots identically to what you see in Robin's video.
> 
> Anyone here ever used any of those Starrett stones?
> --
> Rex


Yes Rex, I have been using a granite surface plate for a very long time for such purposes. I didn’t mention it earlier, sorry, but I also apply some Starrett granite cleaner as I’m doing the deburring. It really helps keep the shiners/skid marks off the surface of the stone if nothing else. The stone I use is about 9” X 12”. That kind of real estate is another big advantage over the smaller examples. I’m seeing on fleaBay that a replacement, if I bought new, would be about 50 bucks. Both the surface plate and sharpening stone are a good solution to deburr. I’m not deburring every day in my shop. It’s not a priority. But, it is a needed capability in my shop from time to time…Dave


----------



## chips&more

Bob Korves said:


> That could be difficult to take to the work, depending on size, shape, and location.  I also agree with Jon that it would only burnish, not remove burs.


Hi Bob, after a surface has been blemished it can no longer be the same. So then what? Do you remove the high spot(s)? Or do you try and push them back to where they were? When I recondition my Bridgeport mill table, I DO NOT RUN A FILE OVER ITS SURFACE. Instead, I have a large flat and heavy piece of cast iron that I slide all over the top of the table. This method burnishes the table. I dislike the thought of filing metal off. That will only change the landscape forever. If my precision whatever has a blemish and I’m concerned about it. I’m not that eager to try and remove it. I would rather burnish it. This of course depends on many factors. But I would try and burnish first…Dave


----------



## tyler machine

Once a clamp, t-nut, 1-2-3 block, part or anything falls on or scratches a softer surface, then yes it's not the same. I can't see rubbing two cast iron surfaces together until both surfaces are free of raised material from scratches or dings. Looks like you would just be asking for them to gall each other and cause more damage.


----------



## Rex Walters

Intuitively, I'd also think that a granite surface plate would be terrible for removing a burr after dinging a precision ground surface. My intuition says a granite plate would only be good for burnishing and not for removing a burr.

Yet Starrett sells a granite stone *expressly* for removing such burrs. Dave also reports success doing the same on a surface plate.

I'm inclined to believe (especially with my humiliating lack of a surface grinder) that a precision ground 2" wide granite parallel might make a passable replacement for a precision ground stone like Robin shows in his video. Robin's stones might work better or faster due to the porosity of an India stone, but a shop grade granite surface plate might actually be cheaper than the commercial $500 stones that Robin mentions (for those of us that can't make our own). 

It might take some time and effort with an abrasive stone cutter or chisel, but a $30 surface plate could make a a half dozen or more small hand stones. I'm tempted to try it. 

This sounds truly outrageous, but I'm also wondering if a granite plate couldn't also be used as the final step to make a "precision ground" India stone. I want to try flattening an India stone on a diamond plate to get it relatively flat, then lapping it on a granite surface plate directly! I'm probably missing something, but I just don't understand why a stone lapped like that would have a substantially different surface than an India stone ground with a diamond wheel.

This is all just a gedanken experiment for me at this point though. I have no experience at all with any of this.
-- 
Rex


----------



## Bob Korves

Rex Walters said:


> Intuitively, I'd also think that a granite surface plate would be terrible for removing a burr after dinging a precision ground surface. My intuition says a granite plate would only be good for burnishing and not for removing a burr.
> 
> Yet Starrett sells a granite stone *expressly* for removing such burrs. Dave also reports success doing the same on a surface plate.
> 
> I'm inclined to believe (especially with my humiliating lack of a surface grinder) that a precision ground 2" wide granite parallel might make a passable replacement for a precision ground stone like Robin shows in his video. Robin's stones might work better or faster due to the porosity of an India stone, but a shop grade granite surface plate might actually be cheaper than the commercial $500 stones that Robin mentions (for those of us that can't make our own).
> 
> It might take some time and effort with an abrasive stone cutter or chisel, but a $30 surface plate could make a a half dozen or more small hand stones. I'm tempted to try it.
> 
> This sounds truly outrageous, but I'm also wondering if a granite plate couldn't also be used as the final step to make a "precision ground" India stone. I want to try flattening an India stone on a diamond plate to get it relatively flat, then lapping it on a granite surface plate directly! I'm probably missing something, but I just don't understand why a stone lapped like that would have a substantially different surface than an India stone ground with a diamond wheel.
> 
> This is all just a gedanken experiment for me at this point though. I have no experience at all with any of this.
> --
> Rex


If you are ever down in Montebello, go to Standridge Granite and talk them out of some cutoffs from making surface plates.  Or any other surface plate maker, or tombstone maker, counter top maker or installer, or whatever.  They should be free or dirt cheap.  I would certainly not try cutting up granite myself.  You will still need something like a surface grinder or similar to get the material flat enough so it will not damage the precision hardened steel surfaces when they are rubbed.  I think the flattened India stones make the most sense over all, and the cost of the stones is negligible in the big picture.  It is like the guys who want to make their own surface plates.  By the time you get together all the stuff needed to make, calibrate, and qualify one, and work the learning curve, the couple/few hundred dollars one costs factory made pales when Standridge can whip out in a short time in a factory to a known and tested quantity.  Why reinvent the wheel?  At some point we should make the parts that all the fancy tooling is designed to help achieve.  I know, life is a journey.  Enjoy the ride.  But, along the road, don't forget to also savor the fruits...

I certainly will not be rubbing hardened steel with burs onto my surface plate that is calibrated to .000030" repeatability and .00015" accuracy over the entire 24x36" surface, and I am sure I would not do so on a small cheap import surface plate, if I had one, either.


----------



## Rex Walters

Bob Korves said:


> By the time you get together all the stuff needed to make, calibrate, and qualify one, and work the learning curve, the couple/few hundred dollars one costs factory made pales when Standridge can whip out in a short time in a factory to a known and tested quantity.



Sorry, Bob. I seem to have riled you.

I'm talking (out of at least one orifice) about breaking a cheap $30 or $40 surface plate into a few pieces to play with, not attempting to flatten granite to surface plate standards in my garage! I'm pretty sure those pieces will have a surface as flat as anything I could make with my (nonexistent) surface grinder and an India stone.

I wouldn't take a piece of hardened steel to anyone's expensive certified plate. 

Those cheap offshore granite plates aren't up to standridge standards, but they are pretty flat and surely flatter than a surface ground piece of soft aluminum oxide, aren't they? They are also cheap enough to use as a stone to remove burrs.

Until you shut me up by sending me a couple of the stones you're making I'll keep thinking out loud since I don't have the means of making my own. ;-)
-- 
Rex


----------



## Bob Korves

Rex Walters said:


> Sorry, Bob. I seem to have riled you.
> 
> I'm talking (out of at least one orifice) about breaking a cheap $30 or $40 surface plate into a few pieces to play with, not attempting to flatten granite to surface plate standards in my garage! I'm pretty sure those pieces will have a surface as flat as anything I could make with my (nonexistent) surface grinder and an India stone.
> 
> I wouldn't take a piece of hardened steel to anyone's expensive certified plate.
> 
> Those cheap offshore granite plates aren't up to standridge standards, but they are pretty flat and surely flatter than a surface ground piece of soft aluminum oxide, aren't they? They are also cheap enough to use as a stone to remove burrs.
> 
> Until you shut me up by sending me a couple of the stones you're making I'll keep thinking out loud since I don't have the means of making my own. ;-)
> --
> Rex


Sorry if it sounded like I was riled, I often write more passionately than I actually feel.  A remnant of strict schooling...

I think I would leave any surface plate intact, even if it is destined for rubbing and lapping.  A small cheap one would be fine for rubbing pieces on.  Then I would find some granite remnants from a counter top installer for hand held stones for rubbing the parts.  They should be flat enough for that (?)


----------



## jbolt

Bob Korves said:


> Sorry if it sounded like I was riled, I often write more passionately than I actually feel.  A remnant of strict schooling...
> 
> I think I would leave any surface plate intact, even if it is destined for rubbing and lapping.  A small cheap one would be fine for rubbing pieces on.  Then I would find some granite remnants from a counter top installer for hand held stones for rubbing the parts.  They should be flat enough for that (?)



Most stone counter tops are polished. That might defeat the purpose. Some stone counter tops are honed leaving a dull finish which might be more appropriate. I would be skeptical of the flatness.


----------



## Dabbler

Bob - I agree with you.  I think if you want a rubbing or burnishing stone that is flat, polished granite isn't nearly flat enough;  it's just shiny.  However there is a cheap substitute that is long wearing and even very slightly abrasive.  

Slate.   I got several broken pieces of 2" thick slate from a pool table manufacturer.  First it is ground, not polished.  It is ground because that's the cheapest way to get really flat.  Second it is open structured so it is very slightly abrasive.  I'd put it in line with Jade sharpening stones - between 10,000 and 30,000.  Besides broken pieces of pool table slate are free.  

Now that all being said, I'm still going with a carborundum stone.  Taking away the upended crater from a ding does NOT hurt your milling table in the least.  I know it  is counter-intuitive, but hear me out:  You can rub a 400 grit *precision ground* carborundum stone on your milling table for years without removing a measurable amount of metal.  

- There is science behind my comments, not just opinion or 30 years experience. In order for an abrasive to cut, there is a minimum pressure on each crystal that is required to begin or enter the cut.  Think of a dull kitchen knife being dragged in the cutting direction at a 45 degree angle onto a lino tile.  If you press, it will catch if you use enough pressure.  Part 2 of this equation is that by diamond grinding the stone you are cutting off the sharp points of the crystals, effectively turning the large majority of them into the equivalent of negative rake lathe tools.  You've greatly increased the needed threshold pressure required to enter the cut. Part 3 is that by flattening and evening the stone, there are 4 to 6 times the contact area.

By preparing the stones in this way, you've increased the required pressure to start taking material by 12 to 50 times that of a 'sharp' stone, and a flat stone won't have any high spots to score your table.  

For those of us who want a pair and are without a surface grinder, I'm sure one of us with a surface grinder can work out a suitable deal with you.

Oh, and by the way, our equivalent of Harbor Fright, Princess Auto, is currently selling 2"X6" combination stones for 2.99 in their 'surplus' section.


----------



## Bob Korves

jbolt said:


> I would be skeptical of the flatness.


Yes.  They are looking for pretty, not flatness...


----------



## Dabbler

To Rex and others on touching up your gauge blocks:  

I recently received as a gift some DoAll gauge blocks to use as shop setup blocks (my precisions ones stay in the case 99% of the time).  I checked with my toolmaker friend and he told me about a marvellous way to recondition them without messing up their accuracy!

He suggests that the first thing to do is to take a fresh sheet of paper - (I found 20 or 30lb stock , heavier the better, works) and place it on your surface plate or flat plate of glass.  Then rub the gauge block firmly on the paper, using it as a polishing medium.  It took all but the worst rust off my gauge blocks!

He hasn't told me what to do next, but possibly the granite block might be step 2...


----------



## mikey

After reading this thread, it reminded me of this video:






Now we know yet another use for a high quality, high dollar Starrett Pink Granite surface plate - to flatten a $4.00 India stone. The surface plate is destroyed but hey, your oil stone is stainless steel ruler flat! It makes me wonder what the tuition is for this school because someone has to pay for that surface plate. 

Of course, my post is tongue in cheek. I just use a 1/2" thick piece of tempered glass and wet/dry sandpaper to get my oil stones flat enough for my use. With a straight edge (straight to 0.8 microns), I get no light once its flat and that's good enough for me. Then again, I'm not honing my measuring tools. If I ever do, I'll go begging Bob Korves for some!


----------



## Doubleeboy

Bob Korves said:


> 7" O.D., 150 grit, 1-1/4" bore, 1/2" wide, 1/8" thick resin bonded media, 100% concentration.  I just ordered one of that description from Shars, p/n 505-2233.  $81.00 plus freight from Shars, $91.00 and free shipping on eBay.  I went with the eBay order, saved about five bucks.  I also ordered the stones today, Norton 6 x 2 x 1" combination aluminum oxide,  part number 05108568.  $15.99 each.




just a heads up for anyone considering buying the Shars 505-2233 wheel, I just received one.  It looks like it was made by drunken chimpanseses , bad chatter marks, 8 thou runout.  With 1018 steel for sacrificial grinding and 150 grit A/O grinding sticks I am making progress but I am an hour later only down to 5 thou runout.  This is going to be a long project just to get the wheel true.  If I had it do over I would have sucked it up and bought a Norton wheel.  The Shars wheel qualifies as barely better than junk IMO and is on par with the quality of smaller HF wheels I have purchased.  More chinese garbage is my view.


----------



## 4GSR

One of my Chinese diamond cup wheels has this problem.  After passing a couple of carbide end mills thru the wheel sharpening the flutes, it started straightening up.  Not perfect, but does the job. Might try surface grinding a piece of carbide and see if it takes some of the high spots out of the wheel.


----------



## Bob Korves

Doubleeboy said:


> just a heads up for anyone considering buying the Shars 505-2233 wheel, I just received one.  It looks like it was made by drunken chimpanseses , bad chatter marks, 8 thou runout.  With 1018 steel for sacrificial grinding and 150 grit A/O grinding sticks I am making progress but I am an hour later only down to 5 thou runout.  This is going to be a long project just to get the wheel true.  If I had it do over I would have sucked it up and bought a Norton wheel.  The Shars wheel qualifies as barely better than junk IMO and is on par with the quality of smaller HF wheels I have purchased.  More chinese garbage is my view.


I finally took my Shars 505-2233 wheel out of the box and actually mounted it on a surface grinder hub.  It fit snug on the wheel adapter, and only had about .001" runout.  That jazzed me up after all the bad feedback from others who have bought it.  It was also reasonably flat, just a few striations at the surface.  The wheel was very close to flat across the face.  It only took me about half an hour to prepare it for grinding flat stones.  Just lucky, I guess...


----------



## Bob Korves

I also FINALLY got the precision ground flat stones (Robin Renzetti style) done today.  Here are a couple 'after the fact' pics of the setups for grinding the large faces and the sides.  If you look carefully, the thin protruding ledges for stoning relief slots are visible along one side corner of each stone, one fine, one coarse.  They were ground together in the same setup in the grinding vise, with the ledges matched against each other for more support.  Also shown is the old mist coolant setup that came with my first Millrite.  It was pretty sad, leaked at every corner, was full of nasty dried coolant, and the nozzle and hose were messed up.  It works good now.  Grinding with mist coolant is wonderful compared to grinding dry, better results and perhaps less mess than doing it dry and having grit all over the area.  Not one drop of coolant left the table, and this was my first try.  The stones are magical.  When you start to rub them together, at first is some resistance, which quickly changes to totally friction less, like glass on ice.  Same on nice looking ground parts and tools.   A little rubbing and it goes friction less -- done!  I spent the entire afternoon rubbing down everything I could find for candidates.  How did I get along without these stones all this time???

Edit: the stones are great for deburring the mag chuck.  Quick, effortless, beautifully smooth and flat.  Also good for the grinding vise.  The mill table will be the next candidate.


----------



## Bob Korves

I helped a friend with making some flat stones.  He is a gunsmith, GunMonkey on HM.  Here are some pics of what we have done:
Instead of doing the "standard" 6" x 2" Renzetti flat stones, he wanted to have some larger and some smaller ones for his gunsmithing work.  We did a 8x2" set for use mostly as bench stones with the work moving,  a ~4" by ~2" all fine grit India set, and a tiny set as well, ground on all surfaces including the ends to be able to get into tight places.  He did all the hands on grinding, a raw beginner grinder hand, slightly behind me....  They all turned out very nice, way better finish than my first ones, which do work just fine.  The diamond wheel has settled into flat and square after using it in ways to promote that shape.  I will be giving my stones an additional finish cut or two to make them as nice.



I would also like to ask any REAL grinder hands out there what they think of the setup for grinding the ends of the small stones.  Does it look safe enough?  It worked fine, but I want to know if I am doing dumb stuff...

And before anyone asks, I do not do this stuff for money, only for fun.  A real hobby machinist!  Please do not ask for me to make you some for compensation, not going there.

Edit:  I finally got a vertical format photo to post correctly!!!


----------



## EmilioG

I suppose anything can flex if it's sticking out too far, so if it were me, (I don't know squat about grinding), I would think that more support
would give a more precise finish. Putting taller blocks on the opposite side of the vise with clamps, sandwhiching the entire stone up to
the last 1/2" or so. More rigidity?? You know more than I do Bob.
Q: Would a better Norton wheel produce a better finish? Would it make a big difference?


----------



## Bob Korves

EmilioG said:


> I suppose anything can flex if it's sticking out too far, so if it were me, (I don't know squat about grinding), I would think that more support
> would give a more precise finish. Putting taller blocks on the opposite side of the vise with clamps, sandwhiching the entire stone up to
> the last 1/2" or so. More rigidity?? You know more than I do Bob.
> Q: Would a better Norton wheel produce a better finish? Would it make a big difference?


Thanks, Emelio.  Yes, that would be a good idea.  Perhaps something like a 1-2-3 block.  Didn't even come to mind at the time.  The friction loads when grinding this stuff are pretty minimal unless you make a mistake with the depth of cut, but the results of something tall and narrow tipping into the wheel can be catastrophic.  Even more so with a hard part tipping into a spinning standard grinding wheel.  Instant explosion.


----------



## Doubleeboy

Bob,  in your photo you have a lot of metal on the back side of the part with that vise, I think it would be fine as long as you are taking light cuts of a tenth or so.  When I did my stones my last 3 passes were 25millionths, I think the force of the flood coolant was more than the force of the grinding wheel.  Not being Robben or a REAL grinding hand I don't know how well they came out, but on my near new chuck on surface grinder the stones skate across the surface with very little force and no lube or any kind.  In my view it was a worthy project. I sure wish I could find those Norton 4 x 2 combo India stones that use to be prevalent in every hardware store.  I have only one and would love to have more , they are a handy size for stoning mills and tools in general.  Nice photos!!

michael


----------



## Bob Korves

EmilioG said:


> Q: Would a better Norton wheel produce a better finish? Would it make a big difference?


The cheap Shars wheel is now doing a fine job.  It was only off about .001" radially when new and had a few striations in the face.  I dressed those out pretty easily.  The wheel has been if beautiful balance from the beginning.  Others who have purchased them have been a lot less happy with what they received.  It took about half an hour to dress out the .001" runout and most of the other imperfections.  Grinding the first two stones pretty much cleaned up the rest, and has been getting better with use.  The wheel needs to be used by plunge cutting the entire wheel face as much as possible to help the final truing of the wheel diameter and face.  For getting the stones really flat it helps a lot to use a small step over on the final couple light passes.

A Norton wheel would be a big help out of the gate.  It will likely be truer and better in every way.  It is just the cost of it...  There are additional issues that can come up from the wheel adapter and the grinder spindle that can and will cause problems no matter how good the wheel is.


----------



## Dabbler

Bob Korves said:


> A Norton wheel would be a big help out of the gate. It will likely be truer and better in every way. It is just the cost of it...




yeah.  the corresponding Norton stone here is over $500, for a 6 incher.  I didn't even inquire about the 7 inch wheel...


----------



## Bob Korves

Here is how to dress and true a diamond wheel:


----------



## rpseguin

Bob, 
I know this thread is old.
What have your results been like with surface grinding flatstones? 
I think Professional Instruments uses an air bearing grinder to grind theirs. 









Bob Korves said:


> The cheap Shars wheel is now doing a fine job. It was only off about .001" radially when new and had a few striations in the face. I dressed those out pretty easily. The wheel has been if beautiful balance from the beginning. Others who have purchased them have been a lot less happy with what they received. It took about half an hour to dress out the .001" runout and most of the other imperfections. Grinding the first two stones pretty much cleaned up the rest, and has been getting better with use. The wheel needs to be used by plunge cutting the entire wheel face as much as possible to help the final truing of the wheel diameter and face. For getting the stones really flat it helps a lot to use a small step over on the final couple light passes.
> 
> A Norton wheel would be a big help out of the gate. It will likely be truer and better in every way. It is just the cost of it... There are additional issues that can come up from the wheel adapter and the grinder spindle that can and will cause problems no matter how good the wheel is.


----------



## Janderso

Since you woke up this thread, I’ll add my $.02
I was fortunate to be invited to Bobs shop to grind my Norton stones.
We spent a few hours grinding them in as Bob is a persnickety devil.
I use my stones all the time.
They are an essential accessory to have in your shop.
Now that I have a surface grinder, I plan on grinding some smaller stones.


----------



## Rex Walters

Bob was also kind enough to help me make a pair.

I do find them extremely useful for removing burrs, though I’d like a much smaller pair for handscraping. Mine are 6” stones so they can sometimes bridge over and won’t completely remove a burr in the middle of the span while I’m still roughing (when the burrs are most pronounced, but before the surface is very flat).

It may be an imaginary improvement, but I make it a habit to rub all surfaces of the stones against each other to ensure that I don’t wear a curve into the faces. 

That is, with two stones A and B, and four larger faces, A, A’, B, and B’, I rub the faces against each other until I hear/feel all four combinations running smoothly: A on B, A on B’, A’ on B, A’ on B’. 

The three plate principal should ensure they remain truly flat this way.

Again, it may be my imagination, but it does sometimes feel like I’ve removed a bit of curvature from one of the faces I’ve just used. I think always rubbing, say, the same two orange faces together would likely be a bad practice and pretty much guarantee you would eventually create a spherical surface (like grinding a mirror for a telescope).


----------



## Janderso

I do rub mine together but re-watching the video, Robin is meticulous about it.


----------



## Bob Korves

Rex Walters said:


> It may be an imaginary improvement, but I make it a habit to rub all surfaces of the stones against each other to ensure that I don’t wear a curve into the faces.


Flat is probably not as important as we might think, Rex.  The flat stones do a fine job on cylindrical surfaces and Morse tapers at taking off burs picked up in service.  That is the antithesis of flat.  "Flat" when talking about flat stones is about how the stones are ground flat so there is a large surface area with no raised points, but with lots of low spots with sharp corners that cut anything that can get into the openings.  As long as there is enough flat surface to support the part being rubbed, there will be no damage to nice and flat shiny surfaces.  And whenever the stones are not cutting, a nice flat and shiny surface will not be damaged, only defects that stick up above the surface, which get removed.  A couple thou over the 6" length of a stone does essentially nothing bad, even though I would rather have them flat, to get a better feel of how many and where the defects are.


----------



## Rex Walters

Bob Korves said:


> A couple thou over the 6" length of a stone does essentially nothing bad.



I’m not sure. You’re essentially saying making the stones smooth is more important than making them flat.

I’m unclear weather diamond grinding the stones does something to the embedded grit, or if the “magic” of the stones is just due to the much lower pressure per unit area when the stones are truly flat.

I think abrasion requires a minimum pressure per unit area. The larger the area, the more pressure required to abrade. Keeping the stones flat ensures the area is as large as possible and prevents abrasion except at burrs or other very small-area defects protruding above the surface.

A cylinder or taper effectively presents a line (or very narrow rectangle) to the stone. If the stone was also bellied, you’d essentially be stoning a point or very small area (like a burr). I think it’s important that the stone be quite flat when stoning a cylinder or taper (or anything for that matter) else you risk abrading the surface.

I’m pretty sure that if I really bear down on a cylinder while stoning that I can scratch the surface even with a precision ground stone (because the area of the line presented is still pretty small). When stoning a large flat surface, I probably can’t apply enough pressure by hand to cause abrasion.

I’m more curious about how they work the more I use them.


----------



## Bob Korves

Rex Walters said:


> I’m not sure. You’re essentially saying making the stones smooth is more important than making them flat.
> 
> I’m unclear weather diamond grinding the stones does something to the embedded grit, or if the “magic” of the stones is just due to the much lower pressure per unit area when the stones are truly flat.
> 
> I think abrasion requires a minimum pressure per unit area. The larger the area, the more pressure required to abrade. Keeping the stones flat ensures the area is as large as possible and prevents abrasion except at burrs or other very small-area defects protruding above the surface.
> 
> A cylinder or taper effectively presents a line (or very narrow rectangle) to the stone. If the stone was also bellied, you’d essentially be stoning a point or very small area (like a burr). I think it’s important that the stone be quite flat when stoning a cylinder or taper (or anything for that matter) else you risk abrading the surface.
> 
> I’m pretty sure that if I really bear down on a cylinder while stoning that I can scratch the surface even with a precision ground stone (because the area of the line presented is still pretty small). When stoning a large flat surface, I probably can’t apply enough pressure by hand to cause abrasion.
> 
> I’m more curious about how they work the more I use them.


Rex, I know that my 1946 B&S surface grinder does not produce flat surfaces.  It has about .0015" of curvature over the 18" length of the mag chuck, and about .0005 over the 6" width.  Many to most hobby shop surface grinders and many commercial machines will have the same issue or worse.  It has been scraped in at some point during it's previous life.  We have ground about 15 precision flat stones so far on my SG.  They all work just fine.  I can rub the stones together and then rub one on a steel surface, hardened or not, no lubricant, with my entire body weight bearing on the stone, and zero galling occurs.  Just shiny metal, less the high spots.  It is a simple matter of adequate surface area in contact with the work and the way that the 'flat' surface spreads the load while the recesses cut anything sticking up.  All the stones we have made on my SG are close enough to "perfect" to work like they should.  They also work very well for de-burring cylindrical and Morse taper tooling, but I would definitely not not put my full weight pressure into those operations, not enough surface area in contact.  The precision stones definitely do a far better job on the curved surfaces than ordinary stones can do, the undamaged surfaces remain unmodified, and the original geometry stays intact.  Robin Renzetti shows stoning curved surfaces with his precision flat stones in one of his videos.

"I’m unclear weather diamond grinding the stones does something to the embedded grit, or if the “magic” of the stones is just due to the much lower pressure per unit area when the stones are truly flat."
It is the latter.  And they just need to be "very" flat...


----------



## Rex Walters

Bob Korves said:


> I can rub the stones together and then rub one on a steel surface, hardened or not, no lubricant, with my entire body weight bearing on the stone, and zero galling occurs.



Yup, though I’ve been afraid to apply much pressure when stoning cylindrical or tapered things.

We agree that it’s the flatness that makes them work, and appear to now be arguing over just how flat they need to be (which is so unlike me — laugh).

I’m pretty sure the requirement to constantly rub (lap) them together makes them flatter than right off the grinder. I believe the constant rubbing isn’t just to eliminate foreign pieces of metal protruding above the surface, it’s also to abrade the stones themselves and keep them flat.

Your grinder produces roughly the same amount of curvature to every face of every stone you’ve made, no? Putting the stones face to face then doubles that error. Right off the grinder, I remember mine felt a little crunchy for the first few rubs, then quickly settled in to that slick feeling of good contact throughout.

I rub all four large faces together until they *all* feel slick and smooth. A with B, A’ with B, A with B’, A’ with B’. The only geometry that would allow this to happen is a quite flat plane, no?

I’m pretty sure they wouldn’t work with a full thou and a half of curvature, but it doesn’t really matter. The stones we made on your grinder definitely do the job, and I’m going to continue rubbing them together constantly even if it’s just a good luck charm!


----------



## Bob Korves

Rex Walters said:


> I’m pretty sure they wouldn’t work with a full thou and a half of curvature, but it doesn’t really matter.


The .0015" is over the length of the 18" chuck, (the chuck actually measured .0012" out of flat, don't want to oversell...   ), so that would be .0004 over the 6" length of the stone, not much. I have experienced the same roughness when rubbing two freshly ground stones together, every time. I think it is swarf that gets into the lower recesses while grinding the stones during the last pass, rather than from abrading the solid stone quickly parallel. And yes, it does go away completely with a few seconds of rubbing them together.


----------



## Bob Korves

The stones are flat and co-planar enough that when you hold one at a very slight angle to a light source, like a fluorescent lamp, you can quite easily see a good reflection of the light in the stone.  It works even better to have strong light from behind you illuminating an object, to get a good view of the reflection on the stone surface.  I have no idea how to quantify how perfectly angular a reflection we are seeing, or how to measure it with simple apparatus, but that might be a good way to determine actual flatness if it could be done to a good enough result to be meaningful.


----------



## middle.road

Janderso said:


> Since you woke up this thread, I’ll add my $.02
> I was fortunate to be invited to Bobs shop to grind my Norton stones.
> We spent a few hours grinding them in as Bob is a persnickety devil.
> I use my stones all the time.
> They are an essential accessory to have in your shop.
> Now that I have a surface grinder, I plan on grinding some smaller stones.


Nothing wrong with waking up a thread.
As I've commented elsewhere, The Central Cali area hobbyist environment seems a lot friendlier than elsewhere.

I scored (3) 4" dia. stones at one of the sales, they're going to some attention. Along with the rest of my stones. 

There's a gent by the name of Lance Baltzley that I came across on YouTube in an Abom vid, his website shows ground norton stones.
https://www.26acremaker.com (no affiliation, just passing on information)
Break out the pocketbook. . .


----------



## Janderso

It looks like he charges about $100 for his time. I saw his set-up, he runs several stones at a time. As I recall, the stones ran about $100 for the pair.
I'm sure he does a good job.
I am fortunate to have a connection
Now that I have a good surface grinder all I need is a diamond wheel for it.
Hmmm, I wonder if I could sell a pair for $150??


----------



## Bob Korves

middle.road said:


> Nothing wrong with waking up a thread.
> As I've commented elsewhere, The Central Cali area hobbyist environment seems a lot friendlier than elsewhere.
> 
> I scored (3) 4" dia. stones at one of the sales, they're going to some attention. Along with the rest of my stones.
> 
> There's a gent by the name of Lance Baltzley that I came across on YouTube in an Abom vid, his website shows ground norton stones.
> https://www.26acremaker.com (no affiliation, just passing on information)
> Break out the pocketbook. . .


I got a chance to talk at length with Lance Baltzley at the last Summer Bash.  Lance is doing a very nice job of making precision flat stones out of ordinary Norton sharpening stones.  It is not a difficult job, but it does require understanding the process and being careful with the details.  Lance's stones show better craftsmanship than mine do, very nice work.  I only do them for my own fun or with friends, so it matters little.  They work just fine.  Robin Renzetti gets a much higher price than Lance does for his, as does the original maker of them that Renzetti copied (and improved) them from.

Dan, you said "I scored (3) 4" dia. stones at one of the sales, they're going to some attention. Along with the rest of my stones."  Making precision flat stones from sharpening stones ruins them for being honing and sharpening stones.  With flat stones, we can remove burs to a very accurate plane, while not changing anything else.  If you tried to sharpen a knife with them, all you would have afterwards is some tiny shiny spots where burs and high spots were leveled.  It would not really sharpen the knife at all.  Also, rubbing a normal sharpening stone against a precision flat stone would only ruin the flat stone, too much pressure at the points of the random grains of the bench stone.  The precision stones have a large parallel surface area and you cannot enough pressure per total area engaged to distort the metal and cut it.  You also cannot make flat stones using bench stones, the surface must be made so that all the high spots are cut down into a flat and parallel surface with tiny recesses between coplanar grit plateaus, and the corners are sharp and do the cutting of things that get down into the recesses.  It is important to properly understand the fundamental differences in what goes on with the precision stones compared to ordinary abrasive stones.  Both have their places, but the kinds of work they do does not really overlap.  -Bob


----------



## middle.road

Yep, there definitely is a science to it.
I guess I should have clarified my statement a bit and detailed that I just need to get them cleaned up and usable for general use. 
Nothing at the level like you, Lance or Robin do up.
One is in decent shape, the other two not so much. No numbers that I can make out on one the two.
I'll hold back the JB64 for special use, I believe that it is a silicone carbide stone. The other two I'm thinking are india stones.


----------



## Bob Korves

middle.road said:


> Yep, there definitely is a science to it.
> I guess I should have clarified my statement a bit and detailed that I just need to get them cleaned up and usable for general use.
> Nothing at the level like you, Lance or Robin do up.
> One is in decent shape, the other two not so much. No numbers that I can make out on one the two.
> I'll hold back the JB64 for special use, I believe that it is a silicone carbide stone. The other two I'm thinking are india stones.
> View attachment 307759


I have always liked those round stones for deburring stuff in the shop, especially machine tables.  I now use my precision ground stones on machine tables and other precision surfaces, and use the few old round stones I have on less fussy stuff.  Even when scraping metal, I like the precision stones more than the round stones with standard grains to deburr after each scraping pass.  I want the scraper to define the surfaces, not the stone, and I think it gets better results, both with accuracy and with how nice the surface looks after scraping it in.  I should probably grind a couple round stones into precision flat stones.  I like the feel of them in my hand when using them for deburring larger surfaces, like machine tables.  -Bob


----------



## Janderso

I finally ordered the Shars diamond wheel for my Brown and Sharpe surface grinder. The last time I took the plunge they were on back order.
I did a show and tell at work for a couple of the line techs. They were so impressed how the stones will remove only the high points and leave the mirror finish alone that they wanted some for themselves.
I decided to have the shop pay for the diamond wheel and the Norton stones, I'll grind them. The benefit, I'll have the wheel 
I hope I get a good wheel.
Bob, If you don't know a guy with a Norton dresser ($500+) what do you do to dress the diamond wheel?


----------



## Dabbler

Janderso said:


> what do you do to dress the diamond wheel?




Ah, some of the youtubers have done just  that recently.  I've never had to do it so I won't try to describe it - I'll only mess it up anyway.  I wish I could remember the 2 or 3 videos i saw on that since Christmas.

Success!  'solid rock machine shop'  has a video entitled
*Truing and dressing a diamond wheel on the surface grinder.*


----------



## Janderso

Janderso said:


> I finally ordered the Shars diamond wheel for my Brown and Sharpe surface grinder. The last time I took the plunge they were on back order.
> I did a show and tell at work for a couple of the line techs. They were so impressed how the stones will remove only the high points and leave the mirror finish alone that they wanted some for themselves.
> I decided to have the shop pay for the diamond wheel and the Norton stones, I'll grind them. The benefit, I'll have the wheel
> I hope I get a good wheel.
> Bob, If you don't know a guy with a Norton dresser ($500+) what do you do to dress the diamond wheel?


Interesting. Cold rolled steel cleaned up the radial runout. The lateral process looks like a real mess.
I'm not building rockets, I may just check and work out the radial issue.


----------



## Janderso

Here is a good article on how to mount and dress a CBN and diamond wheel.
Good information!


			https://graffdiamond.com/files/common/tech-notes-973841.pdf


----------



## 38super

Purchased shop stones from an ebay vendor, if you visit his estore and contact him directly you'll save a bit.
PM if interested.  I am not associated nor sponsored by this vendor.


----------

