Motor woes

Has anybody used Astrosyn 8 wire T180 universal motors?

Specs are as follows - 12v 0.6 amp/phase Res 20 Ohm/phase Inductance
35mH/phase Torque 5.5Kg-cm.

I can't get the damn things to run at anything above a crawl without
missing steps!!

I'm running them in unipolar mode with a home built controller based
on UDN5804B's

Can anybody recommend some reasonably priced size 23 motors available
in the UK - I'm looking for between 5-7Kg-cm holding torque, but with
a reasonable turn of speed.

I want to use .2" lead screws but get better than 12 inches a minute
(which is all these will do).

--
Steve Blackmore
steve@...