Friday, July 6, 2018

Coffin Smoothing Plane Build - Part 1

This might be due to reading some of Joshua Klein's stuff, but I've been interested in wooden bench planes lately.  I've never owned one, nor have I had access to one, so I've never used one.  Richard McGuire did a great video series on making a wooden jack plane.  But I don't care for the Krenov-type planes (like Richard's) that use a cross-pin to wedge the iron.  I'd much rather have an abutment like traditional wooden bench planes.  I did some internet research on wooden bench plane designs, though it sure would have been nice to have a couple of these planes to help with some details.  A few weeks ago I made my first attempt at a wooden smoothing plane
Sketchup model (without shaping) of a coffin smoother
I started off using Sketchup to rough out a design.  Mine is a three-piece construction, but it's different from other laminated designs that I've seen.  In mine, the sides start out 1/2" thick and I cut the 1/4" deep abutments into them before gluing the whole thing together.
Side pieces showing abutments cut out
For this plane, I'm using a standard 2" wide smoothing plane iron from a metal Millers Falls plane.  The center portion of the plane body is 1 9/16" wide.  With the two 1/4" abutments, this allows the iron a little wiggle room for lateral adjustability.

I made my pieces a couple inches longer than final length so that I could drill holes at the ends and insert dowels to keep the parts aligned.  The extra length was cut off later.  I started by cutting the bed angle of 45° and a breast angle of 60°.
Scrap triangle partially reinserted into the hole it came from
Marking the rear extent of the abutment with the plane dry-assembled
For the forward extent of the abutment, I made a temporary narrow wedge (too narrow to be used in the final plane) to mark the line.
Temporary wedge in place for marking forward extent of abutment
(The drill bit is just a spacer and there is a small wedge forcing the temporary wedge to the right side of the plane)
In the picture above, the drill bit is simply a spacer to keep the wedge from going too far down into the throat.  I also have a very small wedge forcing the temporary wedge to the right side of the plane.  This allowed me to make a knife line to mark the forward aspect of the abutment.  I took great care in making the temporary wedge - I wanted the taper to be exactly the same on the left and right so the abutment lines would be accurate.

With the abutment lines knifed in, I sawed and routed the abutment, and cleaned up the saw cuts with a chisel.
A first dry-fit with the final wedge

Managed to get a nice tight fit of the wedge (with iron installed)
Then I did more shaping of the lower portion of the wedge
Here's something I was not sure how to handle: in the area where the pointy prongs of the wedge recede into the abutment, the wall just forward of the abutment is full width and creates a void where shavings could get trapped.
Can you see the void area at bottom of wedge prongs?
To deal with this, I chiseled the side wall to match the prongs.
Left side with area forward of the wedge prong relieved
Plane reassembled and a much smoother transition
With the throat complete I glued up the plane.  The intent was that the dowels would keep the two sides and the center pieces perfectly aligned.  There was a tiny bit of wiggle room and it didn't come out perfectly, but didn't require too much fettling to work OK.
The glue-up
Next time I'll write about the shaping details and what was required to get the plane cutting properly.


  1. That is an interesting take on the 3 piece plane. I am real curious about how the shavings will come out with the detail you chiseled in. Now of my wooden planes have anything like that.

    1. I'd love to see what your wooden bench planes have to direct shavings towards the center of the plane. I know the prongs of the wedge will help with that - I'm just not sure how the sides of throat can help too. Sometimes in trying to replicate old tools like this it's the details that make all the difference.

  2. Really nice work there.
    I like the very methodical approach to the build.
    Like Ralph, I am also curious about the shavings.
    I can't remember how it looks on my wooden smoother plane. It is not with me in the control room right now, but I think I'll take a look at it tonight.


    1. Thanks, Jonas. One thing I've learned is that a methodical approach is so important in my woodwork. I'll report on the shavings next time.