26 February 2011

Hollow and round planes - 3

Working with Sketchup I look further how to sharpen with sandpaper or rouge set on a profile cut with an hollow plane.  Due to the relief angle the bevel of a hollow does not fit its cutted profile, as setting the bevel in contact with the profile covered with an abrasive creates a deeper profile.  To solve this I look at the effect of two variations with the help of sketchup drawings: the ruler trick and sharpening on a different profile.

Using the ruler trick is unorthodox as it is a not done with profiled planes and once used there is no easy way back. On the other hand the used plane blades I have the top is worn out at the edge and are good candidates for using th trick.

To test the effect of the ruler trick set on an angle of 5°.  That's more than the 1 to 3° I expect in real life. So I drew a blade with a relief angle of 15° and cut of the top on 5° and looked at the end profile compared to the original.  Well there is a shadow of a change, but most probably it would be difficult to measure the difference in real life.

 The drawing shows that even after the ruler trick the original profile is unchanged.  I changed the end result from hollow to round, and when I join the two I get a near perfect fit, ... my word.

Another idea is to use a larger profile (covered with an abrasive) to sharpen the bevel to compensate for the difference in profile.  So I looked in Sketchup what profile fits a 10 bevel and found that a 14 is close.

The drawing shows from right to left the plane and its profile.  The profile change when it is set flat to the bevel when the relief is 15°.  And as first the nearly perfect fit of a 10 bevel on a 14 profile.