The old fashioned way of making jar rings was first to take a large
mandrel and wrap it around with a sheet of compounded rubber until the
thickness of the ring was secured. It was then held in place by a
further wrapping of cloth, vulcanized, put in a lathe and cut up into
rings by hand. That manner of procedure, however, was too slow, and it
is to-day done almost wholly by machinery. For example, the rubber is
squirted out of a mammoth tubing machine in the shape of a huge tube,
then slipped on a mandrel and vulcanized. It is then put in an
automatic lathe and revolving swiftly is brought against a sharp
knife blade which cuts ring after ring until the whole is consumed,
without any handling or watching.--_India Rubber World_.
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