I have used Metal Rubber Corporation (Monrovia, California) to rebuild
rubber parts for Ampex tape machines. Metal Rubber does very high-quality
work but prices for one-offs can be higher than you might prefer. Typically
once you have five or more identical parts rebuilt, the price drops
You should have some idea of the hardness of the rubber you need (pinch
rollers are typically 70 durometer or 60 durometer while phonograph idler
pucks can be softer, say 40 or 50 durometer). By now, those Webster-Chicago
idler pucks have hardened so much that you won't be able to determine what
they were when new. I'm guessing they were probably 50 or 60 durometer, but
that's an educated guess. "Durometer" (using the "Shore A" scale) is what
industry folks use to measure hardness of this type of rubber part. There
is some tolerance involved, so when you have a part rebuilt, it's best to
specify the durometer and the tolerance you can accept (for example, "60
durometer plus/minus 5").
The best material to use for this type of idler puck is usually synthetic
rubber (nitrile, sometimes called Buna-N) as it is relatively
chemical-resistant and it lasts a long time under normal use. This is
undoubtedly what the Webster Chicago model 80 pucks were originally (I have
several of these machines also).
If you send any part in for rebuilding -- and the part has a center hole --
I would suggest measuring the size ACCURATELY before you send the part (use
an inside micrometer or find someone who can do this for you) and make a
drawing showing the desired inside diameter of the part to ensure that it is
ground to the correct size. Alternatively, you can measure the diameter of
the shaft and indicate the desired clearance you need. Or you can ask that
the vendor do this for you.
Often the center hole will decrease in size due to the high pressure and
temperature used in the parts that are rebuilt using synthetic rubber.
Vendors who do this type of work have equipment that can accurately grind
open the center hole a few thousandths of an inch (or less than that) after
the outside rubber surface is ground to size.
With equipment manufactured in the 1970s and more recently, you sometimes
find urethane rollers. These are often clear or blue or other colors.
Urethane parts do not require high-temperature/high-pressure to manufacture
(the compound is mixed and poured into a mold) and are typically less
expensive to make, but they typically do not last nearly as long as
synthetic rubber. Also, urethane is more easily attacked by various
Urethane is a newer material, so you will obviously not find it in old wire
recorders. But you should know about it since it is sometimes a
less-expensive option when rebuilding equipment.