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Precision Ground Toolroom Stones

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by Bob Korves, Jun 12, 2017.

  1. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    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...
     
  2. Dabbler

    Dabbler H-M Supporter - Premium Content H-M Supporter-Premium

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    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...
     
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  3. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    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.
     
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  4. tyler machine

    tyler machine United States Iron Registered Member

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

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    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.
     
  6. Dabbler

    Dabbler H-M Supporter - Premium Content H-M Supporter-Premium

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    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.
     
  7. tyler machine

    tyler machine United States Iron Registered Member

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    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.
     
  8. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    The smaller ones sound like a good idea.
     
  9. Dresden

    Dresden United States Iron Registered Member

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    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.
     
  10. thayne_1

    thayne_1 United States Active Member Active Member

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

    countryguy United States Active User Active Member

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    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.
     
    Last edited: Jul 10, 2017
  12. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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

    tyler machine United States Iron Registered Member

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    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?
     
  14. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    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.
     
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  15. Dabbler

    Dabbler H-M Supporter - Premium Content H-M Supporter-Premium

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    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.
     
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  16. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    I am interested in how it turns out. Great prices...
     
  17. tyler machine

    tyler machine United States Iron Registered Member

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

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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

    Dabbler H-M Supporter - Premium Content H-M Supporter-Premium

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    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!
     
    Last edited: Jul 12, 2017
  20. Joe in Oz

    Joe in Oz Australia Active User Active Member

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    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.
     
  21. Rex Walters

    Rex Walters Active Member Active Member

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    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.
     
  22. Rex Walters

    Rex Walters Active Member Active Member

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    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.
     
  23. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    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...
     
  24. Rex Walters

    Rex Walters Active Member Active Member

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    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
     
  25. tyler machine

    tyler machine United States Iron Registered Member

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    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 :disturbed:
    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. :cool 2:
     
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  26. Rex Walters

    Rex Walters Active Member Active Member

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    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.
     
  27. Rex Walters

    Rex Walters Active Member Active Member

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    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
     
  28. tyler machine

    tyler machine United States Iron Registered Member

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    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. :cool 2:
     
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  29. Rex Walters

    Rex Walters Active Member Active Member

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    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
     
  30. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    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!
     

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