# Making semi-precision toolroom stones



## Cadillac (Sep 26, 2018)

I like many other have seen a video on utube of robin renzetti “I think” grind stones on his surface grinder and I knew I needed a set. I have a surface grinder but I do not have the combs or hold down plates that are required to hold material of this kind. 
I had purchased a bunch of diamond plates to touch up carbide and such. Why not use the plates to surface the stones???
 So I made a nice little fixture to hold the plate and support it. 
	

		
			
		

		
	



 The plates are 3x6 I recessed it into the wood and then recessed two magnets into the wood to hold them in place while using. The plates sits proud of the wood surface. 



 Then for storing the rest of them. I built the holder from two pcs. of 3/4. So the top pc. I routed a 3/8 void in the bottom. Then the bottom pc I routed a 1/2 void in the top. So when glued together it has a sizable pocket in the side to store the other grits. 


 Back to the stones. I have a variety stones for deburring and such. So I took one that had some worn areas and all loaded up with material. I started with a 200grit plate squirted a little wd on the plate for lube and ran the stone across with even pressure for about 20 strokes. Flipped and you could see how it was leveling the stone out. Once I got full coverage with the 200 I jumped up to 600 gave it acouple strokes then finished with 1000 I think. 
  I honestly don’t know how the stones robin did are but I can imagine their perfect. That guys knowledge and attention to details is supreme. But the stones I did perform just like how his video showed. No scratching of the surface it just exposes the high spots and takes them down with light pressure. 
  Until I make the hold down combs this process seems to work very well. The plates were bought on amazon for acouple bucks a pc. I ended up getting from 200up to 2000 which is like paper smooth but was well worth the money even before I found this out. I recommend if your in the market for some great stones this method works good and diamond laps are great to have anyway.


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## BaronJ (Sep 26, 2018)

Hi Cadillac,

Very interesting to read your post, I've just ordered a 300 grit diamond plate to do almost exactly what you have done.  In my case to recover a very very old whetstone that has become hollow with use.


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## Cadillac (Sep 26, 2018)

You will like the diamond plates. I went ever 200 between grits. I don’t know what grit would be best to finish with but with the 1000 the coarse side of one of those bench block stones with a fine and coarse on it felt like glass after the treatment. But yet works exactly as said. Be sure to update us on your results. Good luck


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## BaronJ (Sep 27, 2018)

Hi Cadillac,

Will do !  I'm away for the most of the day, it should be an interesting exercise.


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## C-Bag (Sep 27, 2018)

Great tip Cadillac, thanks!

 I have the India stones but are the round ones. But I was shocked how quick through use it went convex on me. I have a set of the HF diamond plates so upon reading your post and thought why not. Took some elbow grease but viola, flat again! The HF's are plastic backed so I used some stick on sandpaper on my little surface plate and it kept the diamond plates perfectly in place while I worked the stone back and forth while rotating every other stroke.


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## kvt (Sep 28, 2018)

Cadillac
which stones did you get from Amazon.   I may have to try this.


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## Cadillac (Sep 28, 2018)

Well I made a mistake I purchased them from eBay. They are like 3”x6”.  I had bought 8” round ones from amazon for a bench grinder. These are rigid too but recommend a backer for the most rigidity.


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## Doubleeboy (Sep 28, 2018)

The Starrett hold downs that Robin Renzetti uses are pretty simple, if you have a surface grinder, you could make your own, or pick em up on ebay, they show up from time to time for not much $.  I bought two sets of stones,to make my precision stones, cheapo no name stones and spendy Norton, they both work excellently after being ground on SG, which is a filthy procedure.


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## Bob Korves (Sep 28, 2018)

Cadillac said:


> I like many other have seen a video on utube of robin renzetti “I think” grind stones on his surface grinder and I knew I needed a set. I have a surface grinder but I do not have the combs or hold down plates that are required to hold material of this kind.
> I had purchased a bunch of diamond plates to touch up carbide and such. Why not use the plates to surface the stones???
> So I made a nice little fixture to hold the plate and support it.
> 
> ...


Look here, Cadillac:
https://www.hobby-machinist.com/threads/precision-ground-toolroom-stones.59776/page-3#post-531410
Start at post 83, then read to the end of the thread.


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## KMoffett (Sep 28, 2018)

Deleted.. wrong thread.


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## Cadillac (Sep 28, 2018)

Bob Korves said:


> Look here, Cadillac:
> https://www.hobby-machinist.com/threads/precision-ground-toolroom-stones.59776/page-3#post-531410
> Start at post 83, then read to the end of the thread.


 
Looks good. I’m gonna hold out to make the combs. They will be useful for many other materials, and I love making stuff. I have acouple diamond wheels. I had bought two like the ones you have. One OD and one face or cup wheel. Then I got two name brand ones from a auction lot so I should be with wheels. 
 Side note I saw you have the same mag chuck as mine. Have you felt the need for a fine pole? I picked up a compound sine mag chuck and it just seems a little more powerful but I haven’t used it on the grinder yet. I haven’t had any problems with mine just curious.


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## Bob Korves (Sep 28, 2018)

Cadillac said:


> Have you felt the need for a fine pole?


The conventional rule of thumb is small poles for small work, large poles for large work.  But in reality it is not that simple.  Small poles make small flux fields at closer spacing, large poles make large flux fields at larger spacing.  It all depends on what you are doing.  Not only is the the field larger or smaller, it is also shorter or taller.  If you put a 6x12" x2" thick plate on both chucks, both will hold the work down just fine.  If you are putting tiny work with big poles, it will hold it down if it is right over a pole, but not at all in between poles.  Conversely, grinding a part 1x1" by 2" tall on a fine pole chuck, the flux will not reach very high into the part and could very possibly be thrown on a fine pole chuck if it is not blocked in.  Of course, it is usually pretty easy to block it in.  It is not so easy to add magnetism where there is none on a coarse pole chuck.  I have a B&S adapter plate that fits my B&S mag chuck perfectly, and matches the big chuck pole spacing, but it transfers magnetism well or poorly to parts on top of the fine pole plate, depending on many things.  I will take some pictures of it...  Done.

The top photo shows the B&S coarse pole mag chuck.  On it is the B&S adapter plate.  Note that the adapter plate notches on the bottom need to straddle the chuck poles for best transfer of magnetism.  On the adapter is a 6" ruler in the front, it is held down very well.  The 1/8" thick bloc behind it with the two holes in it is also held down well.  There is also another ruler on the mag chuck to the left of the adapter.  It is held down marginally, I would not try grinding it like that.  The dressing tool on the right rear of the adapter is held down "adequately" for dressing a grinding wheel.  It has a 3/4" square cross section.  When it is on the main chuck, it is rock solid.  On the left rear side of the adapter, and on the chuck, are two short Rex 95 HSS 5/16" square lathe tools.  The one on the adapter is held down just adequately, the one on the main chuck is barely held down at all.


In the lower photo is a magnetic transfer block with a 3/4" diameter dowel pin in it.  As shown, the transfer block is rigidly held to the chuck, the pin is held down, but it would slide if it was ground in that position and the pin would need to be blocked to prevent that.  With the block turned 90 degrees, it is worthless.  Mounted on the adapter, in any orientation, it is also worthless.  I suppose (but do not know) if it would work a lot better on a fine pole chuck.


So, it is a mixed bag.  I got the 6x18" B&S mag chuck from a friend of a friend for $100, needed major cleanup and grinding the top and bottom in on the grinder.  The handle works smoothly and easily.  It is a good chuck.  I would prefer a fine pole chuck for the work I mostly do, but this one is working out OK for me so far.  The rule for chucks on surface grinders is "be creative, but don't be stupid."  Now I need to go demag some tools...


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## BaronJ (Sep 29, 2018)

Hi Bob,

You mentioned "Demag" !  I'm curious as to what you use.  I do have a home brew device that I use for things like drills and screwdrivers, and that works very well, but is quite limited.


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## Bob Korves (Sep 29, 2018)

Baron, I have an old L-W demagnetizer like this one:
https://www.bidspotter.com/en-us/au...0006/lot-775f4e0a-6ea2-4d58-a4f2-a4cf014ea857
The two top plates combined working area is 6.5 x 11" .  It works great, loud hum.


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## BaronJ (Sep 30, 2018)

Hi Bob,

Thank you for posting that picture, as they say "A thousand words".  My demag is based on an old motor winding, the sort that you see in record players and washing machine pumps.  Everything has been removed except the windings and laminations.  Pull a drill or screwdriver through the middle and it removes any magnetism.  I do wonder seeing that picture if adding a couple of steel plates on top of the laminations would make it more useful.  If I get chance I'll take a picture t


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## BaronJ (Sep 30, 2018)

Hi Bob,

As promised.  Pictures of my demag device.





This is actually the coil from a Bosch washing machine water pump.  On this machine the pump rotor and impeller are all inside a plastic moulding. 
The plastic bits are held in place by a tag that fits into that slot in between the poles.


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## Bob Korves (Sep 30, 2018)

Before having the nice big L-W demagnetizer, all I had to use was my Weller soldering gun, could put smaller pieces like screwdrivers through the loop to the heating tip to demag them.  

Control and demag units like the Electro-matic Neutrofier for electromagnet surface grinder chucks (http://www.em-chicago.com/chuck_controls.html) have programs that reverse the DC current while reducing the voltage in steps to zero over some seconds.  You can watch the rat fur on the chuck flip back and forth, less and less, until it is just laying there, totally non magnetic.  Those are very nice chuck controls.  They also let you dial in the magnetism level you want, which can be important for delicate parts.

Another H-M member and I are currently working on a poor man's version of that, using a potentiometer to manually control the voltage and a drum switch to manually reverse the current.  It works, but still has some glitches...


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## 38super (Sep 6, 2021)

PGS hold down, coarse tooth bandsaw blade cut to length


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