Thanks Andy,

It sliced OK with Makerbot.

I have downloaded Netfabb to see if I can sort out this and other future drawing fails, but there is a whole new vocab to learn. I use Sketchup for quick and dirty prints, but it woefully lacking for anything tricky.

Nick, I found the collet. It had obviously slipped into another dimension through a wormhole on my CNC machine desk and reappeared underneath it, behind some sheet materials.

Cheers,

Rob-T