Precision Ground Toolroom Stones

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.
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Rex
 
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.
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Rex
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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.
 
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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.
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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. ;-)
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Rex
 
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. ;-)
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Rex
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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 (?)
 
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 (?)
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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.
 
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.
 
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...
 
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! :)
 
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.
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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.
 
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