Saturday, November 12, 2011

Turning a Centreless Disc From Thin Material

I'm restoring an elderly Moen lavatory faucet. There's a circular concealment cover for the knob's attachment screw that has gone to ruin; a replacement disc of some sort is in order. Here's a view of the ruined one.

I have some thin black plastic that I think was originally an electrical insulation sheet in the chassis of an old slide projector. Here's a way to make a small, centreless disc from such stuff.

That square of wood is attached to my wood lathe's face plate. A slightly oversize square of the plastic material is adhered to the wood square with carpet tape. I squeezed the thing all over in the wood vise, so that plastic is well and truly stuck there.

With a bit of trial-and-error pencil marking with the work spinning, I managed to mark the diameter I was after (32.5 mm). A very careful approach with the pointy end of a 1/2" skew chisel results in this.

A centreless disc.

A small utility knife blade slid underneath the plastic is helpful for coaxing the material off the wood. Varsol is helpful for getting the tape off the plastic. (Carpet tape's adhesion can be quite amazing.)

And here's my new screw concealment cover.

It fits perfectly, which is a good thing. Had it turned out to be too big, I'd have had to start again and make another one. Once off the face plate, there is no practicable way to alter the size of the disc just a little.

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