"Richard J Kinch" wrote in message
. ..
DeepDiver writes:

So why is the o-ring there? Is it because true Bridgeport mills
have a larger through-hole in the spindle that allows the o-ring to
fit down inside the hole?

The Bridgeport J-head drawbar has a raised step there, not an O-ring, to
center the spacer bushing. The O-ring might just be a cheaper way to
approximate that shape.

The US-made J-Head drawbar I purchased does have a raised step on the
bushing below the hex head; that raised step is faced down and would appear
to be designed to engage the through-hole in the spindle. However, on this
bushing is an o-ring that has been fitted over (and around) the step. In my
mind, the combination stepped-bushing and o-ring is probably more expensive,
not less, to produce.

- Michael