QIC capstan

tony duell ard at p850ug1.demon.co.uk
Tue Nov 17 23:55:14 CST 2015

> For that many rollers and that amount of money, personally I would spend it on a small
> lathe such as a Unimat, Taig or Sherline (I'm a Unimat fanatic myself, I love 'em. A
> vastly underrated machine if there ever was one).

Actually I have a Myford Super 7...

> For sources of hard rubber material I would be looking at spindles and guide rollers from
> old printers, photocopiers, typewriters and other equipment. For example the IBM Selectric
> typewriter guide rollers that go under the platen.

'Rubber' (actually it's almost certainly a synthetic elastomer, but...) decays with time, that after
all is why I/we are repairing these rollers in the first place. So I would rather not use old or NOS
parts as a source of said material. I do not want to repair the rollers and be doing it again
in a few months time.

> Hard rubber can be machined with a sharp bit, it's how forklift wheels and conveyor belt
> rollers etc. are brought to size after remoulding.

IIRC the cutting angle is totally different. If you are not careful the cutter will dig in and being 
an elastomer the workpiece will be totally pulled out of shape. Cooling it will help, not too 
much or it will be as brittle as glass but I am told dry ice (solid CO_2) is about the right
temperature. Getting that is not easy though.

> If you have a vernier or digital caliper then get together some diagrams of what you need
> and I will see if I have anything in that range in my stash of rollers and guide wheels.

I have no problems making measurements (I have the vernier, and a 'tenth's mike' (a 
micrometer with the extra vernier scale on the barrel, not that I need anything like that
accuracy for this job). It's getting the rubber that is the problem.


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