"Norman Billingham" norman.at.tumulus.org.uk wrote in message
...

"SNIP

For some idea of how the rings would look, here's an ebay listing for
some in the US.
http://cgi.ebay.co.uk/6-5-3-4-MDF-Di...d=p1638. m118

Obviously the almost rectangular bits would be fairly simple to cut with
a coping saw, but I'm a bit stumped about how I'd get a taper with the
rings. Are there any places that'll supply the wood and cut it? I very
rarely do any kind of woodwork, so buying a lot of tools isn't going to
happen, although there is a lathe in the shed that I could use, although
I can't see any way of using a lathe to get a taper...

Using a wood lathe it would be fairly simple. Make a false faceplate from
a piece of MDF. Attach to one side of it a pice of wood which will lift
one edge of the mounted work off the faceplate to the angle of taper you
need.

Roughly cut the workpiece circular and mount it on the false plate via
screws in the central waste, with one point on the faceplate and the other
side resting on your previously attached scrap. The back face is now
leaning at the required taper angle, as is the front, but you can now turn
away wood from the front to bring it back parallel with the faceplate,
thereby creating your taper.

Aha.

Now turn the outside circular and finally part off the ring to the
required diameter from the front.

I've since had a second look and I've worked out that I'll need the baffle
to be rectangular rather than round to allow everything to mount up
properly. I presume my best bet would be to start with a circular bit of
MDF, put the taper on, then cut the centre hole out with a coping saw and
square the sides off? I assume it'd be a pain to be working on a big
rectangular bit of MDF on the lathe.

The work will be a bit unbalnced so you'll need to run the lathe slowly to
avoid vibration.

You can do the same thing perfectly easily on a metal lathe as long as it
will swing the diameter.

Now all I need is a couple of scraps of MDF to meddle with.