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kenst
07-24-2015, 01:29 AM
I inherited about 5 8" stones from my dad, problem is, a couple of them have the centers worn down.
What grade ofSilicon Carbide should use to straighten them out.
Also have a couple of granite slabs that are polished on one side and other is smooth, but not polished.
Start off on the unpolished first?
Thanks

Black_Moons
07-24-2015, 05:38 AM
What kind of 'stones'?
Bench grinder stones? Throw them out. They become unsafe with age and rough handling may have damaged them. 'inherited' makes me suspect they may be very old.

Rosco-P
07-24-2015, 07:08 AM
What kind of 'stones'?
Bench grinder stones? Throw them out. They become unsafe with age and rough handling may have damaged them. 'inherited' makes me suspect they may be very old.

No...kidney stones.

Bench stone can be flattened on a surface grinder or a coarse diamond impregnated (sintered?) stone. Similar to: https://www.dmtsharp.com/sharpeners/bench-stones/

bborr01
07-24-2015, 10:04 AM
Ever heard of ringing a grinding wheel? Must be you haven't. I have never heard of grinding wheels becoming unsafe with age. Can you expand on this?

Brian


What kind of 'stones'?
Bench grinder stones? Throw them out. They become unsafe with age and rough handling may have damaged them. 'inherited' makes me suspect they may be very old.

wierdscience
07-24-2015, 10:08 AM
Ever heard of ringing a grinding wheel? Must be you haven't. I have never heard of grinding wheels becoming unsafe with age. Can you expand on this?

Brian

Same here,I'm still working on the pile of 8" bench wheels I bought 20 years ago with no problems.I'm starting to think they get better with age like fine wine ;)

kenst
07-24-2015, 11:56 AM
I should have specified, not grinding wheels, flat stones, 2"x8".
Have a total of 9 big stones, 5 8x2", 4 2x6", and probably 10-12 assorted smaller sizes.

Mcostello
07-24-2015, 10:34 PM
I don't think I've ever heard of anyone "ringing" a bench stone! :) They don't seem to rotate very fast, don't think they will blow up very soon. :)

darryl
07-25-2015, 12:46 AM
Seems to me that bench stones that are worn like you say should be considered worn out and simply replaced. As far as the granite slabs, it's possible they are surface plates. Only one side is ever used, the side which is certified to a certain flatness. Could be they are still useful as is, but this could be an opportunity for you to look at ways of checking the flatness. You might start by deciding whether you need or could use a flat surface, and to what use you might put it. I use mine quite often during an assembly of parts where I want it to not rock when placed on a 'flat' surface like the cross slide table or mill table, and I use it in conjunction with a 123 block to see whether a workpiece is square or not. What you have might still be perfectly suitable for things like this.

kenst
07-25-2015, 02:36 AM
These slabs are drop offs of everything from counter tops, head stones, lab slabs, and have been ground and tested by laser.
Have them as stepping stones, smooth side up not polished, as pedestals for balance scales. Some of them are as big as double sink cutout.
Have a friend that had a job doing the accuracy work for a large company.

dalee100
07-25-2015, 07:16 AM
Hi,

The bench stones can be easily flattened by simply rubbing the concave side on a concrete block or even a flat sidewalk.

Dalee

Lee Cordochorea
07-25-2015, 09:40 AM
There are dozens of kinds of bench stones. Are these synthetic Japanese soft water-stones? White noviculite? Something in between? Some of them need a pretty hard abrasive to flatten. Others can, as has been noted, be flattened quite easily. If they're not marked, only way to know is to try different abrasives.

Mark Rand
07-25-2015, 08:12 PM
Use a sheet of 40 or 80 grit wet & dry paper supported by one of the granite flats, with water as a lubricant. It'll get the stones flat reasonably quickly. The granite flat might not be perfect afterwards if it were a proper surface plate, but I suspect that isn't a problem in this instance.

kenst
07-26-2015, 08:49 AM
Wonderful ideas guys.
One of these methods should work, Mark, you're right, not a lab stone, just have a hard time going through the "valley" and getting anything sharp.

Mcostello
07-26-2015, 09:37 PM
I had a worn out bench stone at work when a thread was posted similar to this one. One answer was to rub it on a brick or somesuch to flatten it. I just used the floor upon which I was standing to the amusement of everyone else. It worked good.

michigan doug
07-26-2015, 10:05 PM
I got a couple from my dad that were similarly sway backed. At about the same time I started using a 400 grit belt on my 1" belt sander, followed by a 1" leather belt with some buffing compound to put the final stropped edge on my various knives and scissors, exactos, drills, etc.

I would never go back to a bench stone. Crazy sharp, crazy fast, doesn't heat the edge if you're even halfway careful, doesn't remove much material. Shaves the hair right off your arm effortlessly. Impress all the girls. Works for axes or mower blades (start with 80 grit if they are rough) down to the finest pocket knife, chisel or plane.