Coping Shoulders

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One of the primary applications of scribing gouges is in making timber shoulders fit waney edges.  This is a straining beam that engages a brace on either end, but the joinery is still a brace mortice, layout at 45º to the axis of timber.

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English framers call this “double-cutting” a shoulder, then scribing to fit.  Keep those reference marks parallel…

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Matt Ross made this chisel some years ago, inspired by a French example.  I can’t say for certain that the cranked handle and flared corners were made just for this purpose, but it damn sure does the job.

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This gouge, all told, has cost me something in the neighborhood of $6k so far, but that’s another story for another time, as is the owner’s mark.  The maker’s mark, at the top of the photo, appears to be RUST, which I believe to be an early 19c English maker.

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The owner’s mark, J L CRIST, was stamped twice.  I imagine him to have been a distant relative of the JESUS H CHRIST whose name I have heard invoked so often in shops and on building sites.  Believe what you will…   There are a lot of gaps in the historical record;  I believe that most people just want a good story.

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The result, as always, speaks for itself.

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Final assembly, pulled tight with come-alongs and straps, measured and diagonals checked, ready to mark draw-bores.  You probably can’t see it, but there’s a string with gage blocks stretched across the shoulders.  This was the trickiest setup I have ever worked with, one click on any ratchet affected everything else.  Precise measurements, btw, are facilitated by driving 3d galvanized box nails at measured points on the layout lines.  3-4-5 for post to beam fit-up; check parallel then pull diagonals on bents.

Recently I was sent a link to a paper titled  The Invisible Tools of the Timber Framer  Well worth reading, but still doesn’t quite reach the bottom of the toolkit.  There are a few tricks in fitting tight shoulders in timber, some of them useful for smaller-scale work as well.  Fitting up irregular stock into mortice and tenon is a challenge, getting a snug fit at the shoulder being the final test.  Dividers help, down to an interval of ⅛” or so, but even the sharpest point jumps and scratches along.  For a quick reference, use a “half-pencil scribe”.  Lay the pencil flat on the receiving timber and draw the point across the meeting surface.  Work parallel to that line.

One of my essential tools is an old 12″ combination square blade with it’s own hand-sewn leather sheath for protection.  I use it as a feeler gage in fitting shoulders, along with a collection of 6″ blades of different thickness.  I also use a Starrett tapered gage, about 3″ long, and several maple and boxwood wedges that make up my gap gages.  Wooden wedges are especially useful when working the underside of a timber assembly; a quick pencil mark across, measure the resulting thickness, map the result.  A sharp mill knife (or something equally robust), a steel straight edge, a carpenter’s pencil shaved to a chisel edge (for lighter work, a regular #2 shaved flat with a block plane and pared down), a #705 ink pencil followed by a spritz of water will leave an indelible green line.

Chalk has it’s place in fitting up, but one must be careful of the mess it leaves behind.  David Pye used the term “offer up and fit” which is particularly the case in fitting a shoulder to an irregular surface.  As the shoulder approaches an ideal fit, I leave a margin of ¼” that will actually contact the surface, then slide a piece of coarse sandpaper through the joint.  The resulting scratches show a marked contrast to chisel or gouge, and paring away those marks will result in a tighter and tighter fit.  This is where those scribing gouges really shine.

 

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About michaellangford2012

Timber framer, boatbuilder, dreamer, writer, musician; collector of books, tools, aphorisms. "There is nothing, absolutely nothing…half so much worth doing…as simply messing about in boats."
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3 Responses to Coping Shoulders

  1. Trying to read what the Arabic script says – on the blade: think it says “belong to…. but the rest seems indecipherable.
    Interesting how an English blade has Arabic in well worn script.

    David.

    • It is a mystery. Some of these old tools have an Excalibur sort of feel to them. Maybe I should throw it into the lake and just see what happens…(Le Mort d’Arthur is a must read at Christmastime.)

  2. Greg Merritt says:

    A thing of beauty! As is that crank-necked slick. The scale and organic nature of timber framing has always impressed and fascinated me. Thanks for this peak behind the curtain on how it is actually done.

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