Friday, January 1, 2010

First Shawm - the Bell!

The bell section forms the bottom 100mm of the shawm.  This will be attached to a foot section about 135mm long, which will slide onto the upper part of the body which has been described in the previous posts.

I didn't have a block of wood large enough to make the bell, so I glued two chunks of rimu together as seen here (note to readers elsewhere in the world: rimu is a timber much used locally for medium quality furniture and house construction - see for more).
As it was, this block was still not quite large enough, and I had to glue some more pieces on here and there.

The bell blank mounted on a faceplate to allow end turning.

I bored a 25mm hole down the axis, with a brace and bit, using the hollow centre as a guide.  It didn't matter whether this was exactly centred but it helped.  Then I drilled two sets of holes with an electric drill, one set in a ring at 61mm diameter to depth 25mm and the other set in a ring at 36mm diameter to 50mm depth.  Taking the faceplate off the lathe, I chiselled out  much of the unwanted wood from the inside of the bell.

Back on the lathe, I did the rough shaping of inside and outside of the bell as seen here.

Checking the internal contour of the bell against a polyester template, printed  actual size from the CAD package.

The original hole I bored to start the turning was not precisely centred.

Here is a small block of wood glued into the base of the bell, and the actual centre re-established by stabbing it with the fixed centre.

I drilled through this new centre with a small drill, providing a guide hole for the next step.

Drilling the socket for the foot section to be glued to the bell, using the centred guide hole from the previous step.

Here is the foot section, with the socket for the upper section cut. The outside is being roughed down to approximate size.

I was not game to cut this socket too vigorously in case I made it too large.  Reaming it later is a safer bet for a good fit.
Here's a detail of the driven centre fitted to the new central hole, filled with a small piece of dowel.

Here's a short reamer I made to tidy the socket on the foot section up to the right internal size.  The cutting edge is the piece of hacksaw blade protruding slightly from the circumference.

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