Hand Tools

The bevel

Wiley Horne--So. Calif.
Hi David,

Here’s a notion. It doesn’t rise to the level of a theory. Just a thought that occurs: Warren’s recommendation of the farthest setback that gets the job done, combined with the rounded bevel, have the effect of reducing friction between shaving and bevel. Bending the chip to a critical angle, rather than ‘breaking’ it. Minimize back-pressure by not letting the bent shaving become a ‘spring’ flexing back onto itself and increasing the pushing force required. He creates just enough friction and back-pressure to get the job done—note in Fig. 6 that the pushing force required at 8 thousandths is only 10% or so greater than ‘no chipbreaker’, and this is with a flat bevel rather than a rounded one. And yet there is concave wear below the chipbreaker at 8thou, showing that the chipbreaker is doing real work on the shaving.

Question: How does the above notion relate to the straightened shaving? I wonder if Warren is going for a straightened shaving, which would seem to require ‘breaking’ the chip, or whether he is trying to find a sweet spot just before physically breaking the shaving.

The picture I see, and maybe it’s incorrect, is that there is a continuum from ‘bend shaving’ to ‘bend to critical angle’ to ‘break shaving to produce straight shaving’, to ‘accordion shaving’—as the bevel steepens and the setback is tightened.


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