Hand Tools

Subject:
Re: More .. (shudder) .. on the chipbreaker :O

ian neuhaus
There again is the recommendation to make it match the edge. "Slightly rounded", but why? So that one can relate an iron laterally and use one side or the other only?

not intending to be condescending ...
it's simple geometry.
If the plane iron is very slightly curved -- which is the recommended shape to avoid plane tracks and to assist with edge jointing -- then it follows that the chip breaker (or back iron) should have the same curvature. Otherwise when a straight chip breaker is set 1/64th back from the edge of the iron near the sides, it will be 1/32 or possibly 1/16th back from the cutting edge in the middle. As Haywood notes, in some woods 1/64th from the cutting edge is the desirable set back. Conversely, if the set back is 1/64th at the center of the iron, the chip breaker will overlap the cutting edge towards the corners of the iron, with all the "chip under the cap iron" problems that will entail.

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