Stepper motor pullies

Posted some pics and info about the Taig CNC mill I'm doing last week
end, post# 47955
Link to one pic repeated here:-
http://homepage.ntlworld.com/machines/taig2.jpg

I needed 6 pulleys to do this, all 22 tooth 5M HTD series.
Unfortunatly the stockist only had 5, rang round and all the other
supplies wanted double the price I paid for these.
Had a look at the specs and found quite a lot of discrepencies.
So I rang Fenners tech section up who I have a good working
relationship with. Told them I need to to cut this pulley direct on
to the end of a motor shaft and didn't have room to mount one, could
they fax me the info. Sure enough the info came through with all the
calculations.
Seems the basis of the 5M series is a semi circle with a diameter of
3.1 mm or 0.122" Once you have this and the pitch circle diameter
it's easy to make these one of three ways.
[1] drill a series of holes on the pcd and then turn down to the OD
[2] Index round and use a 1/8" end mill
[3] Index round and use a convex cutter in a horizontal mill

I chose the later as I had this setup already on the mill. Found a
cutter with a 0.120" rad and cut a new pulley in about 20 minutes.
If there is enough demand I can convert the design details into an
easy to read table and post this in the files section.
What complicates the matter is there are TWO pitch circle diameters.
The usual quoted one is the theoretical belt pitch circle which is
bigger than the OD and the pcd of the hole circles which is never
published in tables, It's this one we need. Once this becomes clear
these are far easier to do than the trapiezoid type of timing belt.

John S.