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268102 Ed Minch <ruby1638@a...> 2019‑03‑13 Dowel plate
Did a fun thing today

On the big big Kalmar Nyckel, trunnels are used for fastenings in many places,
mostly planks on the hull and deck into the framing underneath.  A trunnel is a
wooden dowel that has a slot in both ends.  You put a wedge in one end and drive
it wedge first into a flat bottomed hole.  As it bottoms out, the wedge spreads
the trunnel and locks it in place.  You then drive a wedge into the top.  So the
trunnel is wedged in place at the top and the bottom and acts as a bolt.

The biggest we use is 1-1/4” and driving them into existing holes that old ones
have been taken out of has always been a hassle.  I made a chair devil with a
round recess in the blade that matches the biggest trunnel, and that has worked
well, but I thought that a dowel plate would be faster.  The question in my mind
was could you drive something that big made of Jatoba, a very hard wood, without
crushing the wood or wearing yourself out.  Also, the local machine shop wanted
$200 and another $175 to heat  treat it.

One of the other volunteers is a machinist and he made one to my specs with
1/64” steps either side of 1-1/4”.  I turned up a couple of Jatoba blanks just
big of 1-1/4" and we had at (past tense of "have at’).  Here is a picture:


It did a passable job with reasonable effort - actually once it was sized at the
biggest hole, the 1/64” steps were fairly easy.  But you could see a ring at the
start of each blow that was a little off of the finish of the travel of that
blow.  Then my machinist mate had an idea - we stuck one in the 20 ton press and
shoved it smoothly through and it it made a beautiful thing.  Just the hint of a
bow along it’s 7” length, but good enough for shipbuilding.  So now we can make
our own accurate trunnels without a drawknife and shave horse, but still be

How cool is that

Ed Minch

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