Discussion Forum
I recently purchased a set of chisels to replace a set ‘that went missing [I’m being polite]’. My first set had reasonably straight and reasonably flat backs, which made polishing a flat back a necessary but not unpleasant task.
When I began to ‘flatten’ the back I noticed that only the tip of the chisel and the point of contact at the edge of the honing surface were being abraded, and it took a great deal of work to get a consistent flat scratch pattern [which would allow me to move to the next finer grade, and next, etc.]. Being a hobbiest, I suspected my technigue, but this was repeated when I worked the second chisel.
I held each chisel against an engineers edge and discovered that depending on the length there is a 1 mm to 1.5 mm bow along the length of the chisel.
The results is that I now have two chisels (of eleven) that are polished but not in alignment, by an admittedly small amount, with the edge of the blade.
Is this a common problem or a sign of a poorly made tool? What is reasonable to expect from a set that cost ~$250.
TIA,
Ken Leitner
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Replies
Ken,
I went back into our shop and checked the chisels we have and many of them are less than perfecty flat, including several of my own. The curvature ran in both directions, but the majority were out of flat like yours with a slight upward curve. Not too surprisingly, the chisels with the shorter or thicker blades were generally flatter than the long slim bladed chisels.
Because chisels are generally used freehand, with usually only a short area of the back against the workpiece, there isn't a lot to be gained by having the entire length of the chisel perfectly flat.
I have always just worried about flattening the small area of the chisel's back behind the cutting edge, the first inch or so at most. I usually do this with small hand held diamond stones. I do this primarily to get a good sharp edge on the tool, not to tune up the chisel like you might a plane's sole.
Other's might have a different opinion on this. You should post your question on the Knots section of our site, I'm sure this will generate some passionate debate.
John White
Edited 12/7/2006 11:24 am ET by JohnWW
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