Thread: Charnley Forest hone lapping question

Hello Everyone !

I've bought a Charnley Forest hone couple of days ago...it wasn't lapped so I did it with a DMT 220 extra coarse, finally it became flat, but the surface of the hone is not the "smoothest" because of the DMT. So what can I do to make it superb smooth ? Is it a good idea to put some high grit water sandpaper on the opposite side of the DMT and refine the surface on it ? Or any idea?

Does gun oil works on it ?

Thank you very much !

Yes, fine oilstones work best when they are smoothed a bit more than that. I'd recommend going to at least 600 grit, you can probably use the back of your diamond plate as a flat surface to lap with the abrasive sheet, check it for flatness first though unless you don't mind it being a little out. An easy way to check it for flatness is to lap two softer stones then put them lapped sides together and check for gaps between. After lapping the stone take an old wide chisel or something similar and burnish the surface of the stone evenly for a while to finish smoothing it out. Start with light pressure, then after covering the surface of the stone several times go to medium pressure, then do the same and finally switch to heavy pressure and do it one last time. The whole process should last 20 - 30 minutes. At the end you should have a finishing surface that's as good as you're going to get with that stone.

Thanks a lot, one more question....does the chisel scratch the surface of the hone ? Is it possible to refine after the "chisel method" with a coticule slurry stone or it's a spare movement?

Sorry one more question...do I have to use oil on it with the chisel?

Poor DMT

I'm sure you could lap it with sandpaper at the back of the DMT. Personally I prefer sandpaper on a flat surface.

The chisel trick could work but I don't think you need to.

For a smooth finish you can lap it to 600 grit for a superbly smooth finish lap it to 1k or finer.

I disagree on that quite thoroughly. The chisel burnish is what will give you the smooth edge you want on a straight razor. This stone is novaculite, just like an Arkansas, and that step is an important one for smoothness of your razor edge. If you only want to use it for woodworking tools then it isn't really necessary.

The chisel will not scratch the stone as long as you keep the bevel aligned. I have a specific chisel set aside just for this that I put a convex bevel on to make it easier not to scratch the stone by getting out of alignment. I use oil exclusively on stones that are this hard - oil will let the stone do more cutting, where water will do more burnishing or polishing than cutting. The coticule lapping will be unnecessary - if you want to do it, do it before the chisel burnishing.

As far as lapping goes, the best (fastest) way to do it on a stone of this hardness is to use loose grit SiC for lapping on granite, glass or a cast iron lapping plate, but if you don't do a lot of lapping just go with the abrasive sheet.

Originally Posted by eKretz

I disagree on that quite thoroughly. The chisel burnish is what will give you the smooth edge you want on a straight razor. This stone is novaculite, just like an Arkansas, and that step is an important one for smoothness of your razor edge. If you only want to use it for woodworking tools then it isn't really necessary.

The chisel will not scratch the stone as long as you keep the bevel aligned. I have a specific chisel set aside just for this that I put a convex bevel on to make it easier not to scratch the stone by getting out of alignment. I use oil exclusively on stones that are this hard - oil will let the stone do more cutting, where water will do more burnishing or polishing than cutting. The coticule lapping will be unnecessary - if you want to do it, do it before the chisel burnishing.

As far as lapping goes, the best (fastest) way to do it on a stone of this hardness is to use loose grit SiC for lapping on granite, glass or a cast iron lapping plate, but if you don't do a lot of lapping just go with the abrasive sheet.

Just wondering is this method (the chisel lapping) works on all hard stones (chineese, jap. nats, coticules etc...)?

Yes it will work on all hard stones, but on Jnats for instance, the use of a nagura stone makes using a chisel redundant. Most Jnats will self-slurry if you try to chisel-burnish them anyway. It can be a useful technique but is best for very hard stones that do not shed much grit. It works well for the Cnat or PHIG from the feedback I got from a guy who I recommended to try it, probably wouldn't be much use on a coticule.

Thanks mate !

Let us know how it goes!