30 December 2013

The quality of cheap

Where expensive planes are to be used as such,  really cheap planes or worn antiques are more open to more drastic interventions.  In this case I look at sole flatness.

When I look at the definition of the relief angle of a plane blade (in this case drawn by Ron Hock, angle d), I may search how far I want to extend the relief. More with a thick Hock blade of course,  but is 2" even better? That's because if I consider planing over a knot,  the harder knot will push the plane up after being cut, reducing the pressure on the mouth and create a shadow zone behind the knot where I expect planing to be less perfect.
Looking at a Leonard Lee drawing about lapping,  he seems to accept an extension of the relief up to the heel of the plane. As only three small zones: at the toe,  the mouth and the heel need to be included in lapping
The idea of unflattened soles can be found back in discussions about the sole geometry of high performance Japanese planes.  The advantage is also that less downward force is needed to maintain the same amount of pressure on the mouth.

That's the theory, for the practice Caspar Labarre from Amsterdam did a few posts on the subject on woodworking.nl
Looking at his pictures one can see that he files away a minimal amount of aproximately 0.1mm (4 thou) on 50% of the sole,   in between the toe and the mouth and by extending the relief up to halfway the heel.  The picture shows, what I think is, a set of cheap Anant planes fine tuned to be on par with the best planes.
After filing the planes are carefully lapped.  As half the sole is already removed this goes faster and that is good for the precision.  He proposes to lap on a narrow band of sandpaper as wide as the sole.  By this the sandpaper has an even wear over its full width and that makes a perfectly flat sole more likely.