On 2012-03-27, Jon Anderson wrote:
On 3/26/2012 2:01 PM, Noddy wrote:

I've been more than happy with the machine's original J head, and the
only reason I'm playing around with this now is because it's (so far at
least) a zero cost option. Ideally, if I could somehow get the machine
swapped from a stepped pulley to variable speed drive without spending a
lot of money I'd be happy.

Well... my shop CNC for some years was an older Millport converted. It's
a step pulley head, and I ran it with a VFD. I'm converting it back to
manual. Moving down under soon, and pondered which to keep, my J2 BP or
the Millport. I've put enough miles on the BP to replace the VS sheave
bushings twice. The Millport with VFD gives me a wider range of speeds,
and is quieter. All it needs is belts and bearings to freshen the head,
which I can source fairly readily. J2 VS parts, I'd probably have to
have shipped from the States.

You should be able to just do a straight up swap on the two heads. I
thought you had a Series II head, which is something of a monster by
comparison. But given you have a lot of QC tooling, sell the VS head,
buy a VFD, and you'll probably still have some money left over.

Another reason for keeping the step pulley and using a VFD is
that your power bill will go down significantly. When Bridgeport went
from the manual to the variable speed in the J series heads, they had to
increase the horsepower to make up for that lost to friction in the
belts of the vari-speed pulley.

Good Luck,
DoN.

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