On Fri, 16 Jan 2009 21:03:29 +0100, Nick Mueller wrote:

Michael Gray wrote:

which is to be 6.369 tpi

Or almost a 4 mm pitch (3.988 mm)

Nick

Thanks to all and sundry for their help and advice. I have a 110vac gear
motor that I'll put on the leadscrew and have a go with that, using my
favourite old light dimmer as a speed controller.
Pics will appear later at a Photobucket address.
again, many thanks,
Mike in BC