I finally got around to rebuilding the upper hydraulic assembly on my
Clausing 5914 variable-speed lathe. This assembly is attached to the
speed control knob at the top of the lathe. (The lower assembly is what
controls the VS pulley on the motor.)

The rebuild consisted of taking the hydraulics completely apart,
completing the deburring, carefully cleaning everything, and replacing
two O-rings and one V-packing. I bought the rings and packing from
Clausing for small dollars.

The insides were in perfect condition, although there was some grit in
the oil.

The piston is machined from aluminum (6061?) and coated with a slippery
but somewhat hard black coating. (It does not look or feel like the
green coating on the VS pulley hub.) This coating is why the piston has
not galled and seized to the aluminum body of the assembly.

The whole project took a few hours, because I was being careful, having
never done this repair before.

Bleeding air from the system is still a nuisance, and I now know more of
why. The oil reservoir is too small, so when the piston pulls back
uncovering the feed ports, the flow is large and abrupt enough for it to
suck more air into the system. One dodge is to go half the speed range
at first, until most of the air has been expelled.

Another dodge that I may try is to cobble a temporary extension
reservoir that plugs into the Gits oiler at the top of the assembly,
sealed with an O-ring.

Anyway, the lathe can now go as slow as 400 rpm (on the scale), versus
600 or 700 rpm before. I bet that when I get *all* the air out, it will
go all the way to 250 rpm.

Joe Gwinn