Air spindles

Hi,

I'm trying to understand how air spindles work and decide how practical it
might be for me to make a small one for some miniature engraving work I need
to do. Does anyone have any links to sites with cutaway drawings of these
beasts or perhaps a dismantled one on the bench which they could post a
photo of somewhere? Thanks,

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk