I picked up a pair of Ice Bear flattening stones which are quite out of flat themselves.
Is it normal for flattening stones to come way out of flat?
Working on flattening the first one on plate glass and some 180 grit wet dry paper. Not going so fast, might have to stop and pick up some 80 grit wet/dry to speed this along.
One would expect you wouldn't need to flatten that which is supposed to flatten the other stones straight from the factory!
Alan
Some people use carborundom grit on a piece of glass. They now also sell diamond dust. Used for the same purpose.
Max,
This is a concept I never have understood because the grit eats away at the glass, too. Doesn't this defeat the purpose of using it as a reference?
Bob
Glass is very hard. It does etch the surface but the stone flattens quicker. Glass is cheap and disposable. m
"Bob" wrote in news:v2oqd.5736$ snipped-for-privacy@newsread1.news.pas.earthlink.net:
Glass is harder than steel, but very brittle. One doesn't use steel to cut glass, they have diamond glass cutters, or special tips to scratch the glass.
May have to make a trip to the lapidary supply house here in town and get some flattening grit. I tried a belt sander 80 grit cubic zirconia belt, but wetting it with the stone caused the edges to curl.
Alan
Actually, I sharpen all of my edges on 12 inch diamond bench stones. I also flatten my Japanese and water stones on the diamond stones. max
I'm curious about this, also. The explanations I've read about lapping say that the lapping compound becomes imbedded in the softer material and abrades the harder material. I'd expect that this isn't an all or nothing proposition and that both surfaces would be abraded, to a greater or lesser degree.
Any lapping I've done using glass has the glass covered with (disposable) wet/dry abrasive paper, so I assume that I've not abraded the glass at all.
I wonder if covering the glass with contact paper (or something similar, but sturdier) would work, using lapping compound?
R, Tom Q.
Glass is harder than some (most ?) steels, but I don't think it's harder than all steels. I may be mistaken about that.
In any case, the glass is likely softer than the stone that the OP is flattening and also softer than the lapping compound being used.
I'm guessing that the glass plate _is_ being worn.
R, Tom Q.
the gemstone world uses a scale of hardness called Moh's. on Moh's scale, glass and steel are both 5. silicon carbide, the stuff that cheap sharpening stones and the grit of wet/dry sandpaper are made of is 9 on Moh's scake. the roller wheels on glass cutters are made of hard steel, pretty much the same stuff as files are made of. you can also get them in carbide, but that's beside the point- the steel ones work fine.
a good hard glass like pyrex is harder than soft steel, but the steel will still scratch it.
I do lapping and honing as part of my "real" job, so this is going accurate in a real world sorta way, altho maybe not textbook....
...Honing is using an abrasive that is fixed in a matrix, usually just the grit with glue...ie a stone.
...lapping uses a loose grit that gets embedded in a "soft" plate or mandrel. "soft" means that it's softer than the steel or iron that you are trying to sharpen or shape. almost all the time, there is some sort of lube used...light oil, olive oil, kerosene, fuel oil or water being the most common lubes. about the only exception to the soft vs. hard is when doing cast iron...flattening the sole of a plane, for example...in that case, both parts will be abraded, so watch VERY closely to make sure that you aren't destroying one while trying to flatten the other...it is possible to get both flat but you do have to be careful and pay attention.
As for using glass as a lapping plate, altho iron works better, glass is easier to get, is much cheap and can be thrown out when bad things happen. Glass is MUCH more brittle than iron, but it's surface hardness is actually pretty soft and will allow the lapping grit to embed and do it's job. That is, as long as you don't try to use a very course grit compound, so anything courser than about 240 grit, use MDF for the plate.
Any question, feel free to Email me and I'll try to clear them up.
Mike
the glass is definitely being worn.
That's because of the carbon (carbides) in the iron matrix.
the action of a roller wheel glass cutter is kind of a special case in the cutting tool universe. glass is an amorphous solid- sort of a supercooled liquid- held together by surface tension. the steel wheel has compressive strength greater than the surface tension of the glass, so it crushes the surface of the glass even though it's not significantly harder than the glass. the break in the surface of the sheet of glass makes it easy to break cleanly along the line.
... not to pick nits, but on the moh scale, a substance will not be scratched by something that is softer than itself; it can only be scratched by a material the same hardness, or harder. Thus, if the pyrex is scratched by soft steel, it must be the same hardness or softer than the steel. (IIRC, that was one of the identification methods for identifying minerals). A softer substance may leave a mark, i.e. part of itself on a harder material, one would have to remove the mark to determine that no scratching had occurred.
this is the weakness of scratch tests. a substance that is stronger will scratch a substance that is slightly harder, but weaker. soft steel scratching hard glass is a perfect example.
now, steel and glass are both manmade materials, with a wide range of specific composition and a wide range of properties, including hardness.
If you get a third stone you can flatten them against each other. I'll leave it to you to determine why two stones are insufficient for this.
-j
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