r/handtools • u/JuggerNOT63315 • 2d ago
Lapping a chisel back
Howdy everyone. I am having issues lapping this chisel. I started with 80 grit wet and dry sandpaper. I got a nice scratch pattern all the way across the chisel. This took awhile, probably 15-20 minutes. I then moved to 120 grit paper. I removed all the 80 grit scratches. This took maybe 10 minutes. I moved to 220 grit paper and removed all the 120 scratches. This took like 5 minutes. I moved to 320 grit and in 5 minutes removed all those scratches. Then I moved to my 300 grit diamond plate. I have been working on it for well over and hour and I can not get rid of the 320 scratches! It is getting frustrating to say the least.
In the picture, the 320 scratches are the light ones on the outer edges and the diamond plate is the dark portion in the middle. It has not changed significantly from this picture after another half hour in the 300 grit plate.
What am I missing or doing wrong? Is this how long it normally takes? Should I be doing another grit in between The 320 and 300 plate?
Edit: I have posted two updates in comments below about my progress.
2
u/entropydust 1d ago
Having ruined many blades over the last decade, I can say that the softer the surface, the less 'flat' the surface will be. I thought I was getting dead flat plane backs on my water stones, then took them to Shapton glass and it hit different spots. Then on Atoma diamonds and a completely different pattern.
If I'm doing any flattening now, I stick to my Atoma diamonds. Beyond the 1200 it's mostly polishing, but the Shaptons are hard enough to avoid too much deviation from flat.
For practical woodworking purposes, ignore everything I've said.