Friday, July 13, 2018

Coffin Smoothing Plane Build - Part 2

Part 1 of this build showed the general construction of the plane body.  This post will highlight some shaping details and the work required to get the plane cutting smoothly.

But first, I couldn't help but try the plane after it was glued up.
First shavings - test cuts were OK
After the glue had set, I cut off the extra length at each end - the final overall length is 7 1/2".  Then I did some typical shaping of a coffin smoothing plane body.
The plane body shaped
The back end was rounded over using chisel and rasp and the sides were curved using a chisel and plane to make the coffin shape.  The upper 3/8" of each side was chamfered, and the chamfer was extended half way down the front and back ends of the sides.

One detail that I see on most wooden bench planes is the "eye".  That is the little "teardrop" chamfer shape on both sides where the throat meets the top of the plane body.  I never knew what the purpose of this feature was, but now I know it is not just decorative.  Using wooden planes requires a lot of reaching the fingers in the throat to pull out shavings.  Without these "eyes", the sharp edge of the throat would scrape the fingers as you pull out shavings.

The final step for the body was to flatten the bottom.  I did this first with a metal-body smoothing plane and then rubbed the sole on sandpaper glued to plate glass.  Next I completed the shaping of the wedge.
The completed wedge shape
Boiled linseed oil was used for a finish - three coats over three days.

When I tried the plane out, I was getting some "chatter" and the surface left by the plane clearly showed the problem.
Chatter shows up easily in an enlarged photo - not sure if you'll see it here
Chatter plainly seen in this edge cut
I skewed the iron a little so that the right side of the iron receded into the plane body.  This resulted in a shaving that clearly showed chatter problems.
A face grain shaving showing chatter issues
I tried skewing the plane and the performance improved, but did not eliminate the chatter.  I googled the problem and found a video that Bob Rosaieski had done on how to diagnose and fix this problem on wooden planes.  The link is here.  In the video, Bob coats the back of the iron with soot from a burning candle.  Then he assembles the plane with iron and wedge, taps the back end of the iron to move it slightly and looks to see where the soot has been left on the bed.

This worked perfectly for me.  It clearly showed where the high spots were - I had an area on one side of the mouth where the iron was not touching the bed.  After paring away the high spots (this took several iterations with the candle and paring), I got the bed flat and the iron started cutting properly.

Here she is, all done and fettled.  The bed angle is 45* and the breast angle is 60* (don't know why, but my keyboard shortcut for the degree symbol of <alt>248 doesn't work anymore).  The wedge angle is 10 or 12*, I forget which.  The plane body is 2 9/16" wide at its widest point and is about 2 5/8" tall.
Glamour shot
I don't know at this point whether this plane will become a regular user, but at the very least it is proof-of-concept about this method of plane building.  I hope to build a wooden jack plane sometime in the not-too-distant future and possibly even a try plane.  Gotta find some irons that are more appropriate for that, though - the iron in this smoother is a thin Millers Falls iron from a metal smoothing plane.

If you'd care to comment, I'd love to know about your experiences in building similar planes.