01 August 2013

How did Roubo do

After letting Roubo outsource his massive mortises to carpenters in the previous post,  I discovered a different idea reading the Lostartpress blog.  Chris Schwarz drilled then saw his mortises with a jigsaw and finished with a chisel.

Jigsaw joinery can be fun, fast and sometimes appropriate. For example used in exterior structures like guardrails. The tenons are in this case best cut on the spot and mortises come where tenons end. I made a test piece a few years back while developing my technique, from right to left.
  1. first try with a circular saw and chisel but the tenon is all jigsaw as it involves upwards diagonal cuts
  2. drilled through with jigsaw 
  3. stopped with a short jigsaw sawblade and drawbored
  4. No. 3 is ok, more of that
  5. angled 
Back to Roubo,  I don't expect that he used a jigsaw but a frame saw is a good idea for a through mortise.  Looking at plate 12 fig.5,13,14 we can see a scie à tourner a frame saw with a 1/2" blade.  After drilling a hole it is quite easy for a trained professional to cut out the mortise to the line.  If the Vagnmakeri på Söder movie from 1932 is an indication (at 15:00) it will take only a few minutes to do the sawing .

Nowadays it is uncommon to find through mortises in a bench top. Probably with reason as seeing for example tenons come and go through the top with seasonal changes offers little added value.  Up to now I have two reasons to do it: It is sturdier,  Roubo for example wedges the tenons at the top.  It is easier to make,  by lack of a chain mortiser or something similar through mortises are sometimes simpler.

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