Thread: Why should I use powder to dress my stone?

Hi Euclid440, I checked the stone on the lapping table like I would check a split pump casing. I am confident the stone is flat. I have not lapped the stone with any grit at all. I don't understand why I would need to do that. I bought the stone from a well known company and it was high quality. The stone is extremely smooth. I paid a fair price from the stone and don't want to dress it with any grit if I don't understand what it will do, like I said I paid a fair price for the stone. I think I will ask one of the geologists here at work what they think about it and see what they think lapping novaculite will do to the surface of the stone. It may take me a while to get an answer but when I do I will post it to this thread.

If it is lapped flat you can “make” the stone act finer by polishing and burnishing the face. The grit in an Arkansas doesn’t release like a jnat or water stone. It is much more akin to a diamond plate. As the plate gets used the tops of the diamonds get flattened and rounded which makes the stone cut less quickly as well as leaves much shallower stria in the steel. So if your edges are comfortable enough or keen enough try rubbing some bar on steel knife or chisel or plane blade on it for a bit then run a razor on it and test shave it.

My ark’s are polished to about 2k then burnished until I started to get my edge where I like it. The versatility of these stones is immense. The other rabbit hole with them is lubricants. There are tons of threads on them around here.

Jeff, all Arkansas stone are pricy, and all the well-known Ark companies sell quality stones, but they do not have time to lap the stones dead flat. Many are sold to knife or tool sharpeners where dead flat is not critical and relatively flat is good enough.

Many people repeat that float glass is dead flat, it is not, and not needed to be to look through it, but it is easy to make flat with a bit of Silicone Carbide and a flat surface.

Some Ark companies are better than others at flattening but still, they are not “completely” flat or defect free. Maybe you got lucky and got one that is. Lapping will not only get you flat but a uniform finish, from a known grit. One that will polish a razor bevel better and produce a finer edge.

You do not know what grit your stone was finished to and if whatever finish that is good enough for you, fine. Lord knows most of the vintage hard Arks were never flattened and are burnished smooth from years of hard use, they can produce fine edges without lapping.

It is not so much that they are dead flat but that they are completely smooth, defect free. The only way to ensure that a stone is completely smooth is to make it dead flat to a uniform surface with a known grit. With an Ark, you only need to do it once.

I would have thought that an Optical flat would show any surface imperfections, but as Tom Lipton shows in the video below it will show overall flatness but not always imperfections in steel from corrosion.

If the corroded steel tool makers flat, (12:01) were a stone, and the corrosion were stone defects of the same size and depth, they would affect the finish quality of the finish they could produce on a razor edge.
What you want to know is not so much flatness, but if there are any dips or defects. But to remove dips and defect, you must flatten. Silicone Carbide is an inexpensive way to flatten, you can use diamonds, but is more expensive than Silicone Carbide.

The translator itself, in this video is interesting. I did not know that.

Russian Optical Flat Testing

I have to disagree with the fact that you only have to lap an ark once. I inherited a bunch of arks from my dad who had a sharpening business and several of them were bellied in the center. His business was mostly concentrated on saws and knives and not so much on razors although he did do some. Either way he never used the arcs on razors, only knives. Some of his stones were bellied like crazy. I had to flatten then lap every single one of them. Do yourself a favor and lap it if for no other reason than for the sake of taking that out of your mind.

Well, let me be a little bit more specific. In fairness he did not use them for razors, only knives and probably applied more pressure than you would with a razor. I do know though that he flattened his stones because I've seen him do it. One of his sharpening machines had a lapping wheel and he had various cans full of powders. I don't know that I saw him flatten these specific ones but he did flatten his stones. More to the point though some of his arks were visibly bellied which takes a lot because novaculite is so hard. Some of them though did not look bellied but when I lapped them you could see the belly at that point. Most of them had a pronounced X through the middle from the X stroke he used. So I guess the take away from that I'm trying to impress is you can look at a stone and it seems dead flat. You can even use a straight edge and it appears pretty much flat but once you put it on a lapping plate you can see that it is not. If you just buy some inexpensive lapping compound and a good flat hard surface and run it over it then you've removed that as an obstacle.