In trying to replace the vernier drives in my HW-101, I made a boo-
boo. I bought the metric version, had them machined, and only found
out when I tried to install them into my set. OOPS!
For sale are (2) Jackson Bros (now Mainline Group) 6:1 ball drives,
JUST LIKE the ones in the HW-101 and similar sets, but the 6mm type.
Look here for specifications:
http://www.mainlinegroup.co.uk/jacksonbrothers/4511.htm
The shafts have been cut down to 1/4" on a lathe with a little
chamfer. However, all hardware is present; hex grub screws and small
brass screws for mounting a tuning dial.
Asking $5 each plus shipping.