I have a Hardinge HC on which the spindle speed control jack screw
motor is not turning.
Not sure if it is an electrical problem or what. Everything else
works on the machine and the spindle spins nice and quiet, but I
can't adjust the speed with the knobs.
The nut is down at the bottom of the jack screw.
Somebody who has an HC says that he's seen those machines do that, and
to kick the motor while in speed 2 and adjust the pot/knob up. I
tried that, starting from light kicks to pretty firm, but no luck.

Looking for suggestions on how to fix it.

On Thu, 13 Mar 2008 15:21:00 -0700 (PDT), rpseguin
wrote:

I have a Hardinge HC on which the spindle speed control jack screw
motor is not turning.
Not sure if it is an electrical problem or what. Everything else
works on the machine and the spindle spins nice and quiet, but I
can't adjust the speed with the knobs.
The nut is down at the bottom of the jack screw.
Somebody who has an HC says that he's seen those machines do that, and
to kick the motor while in speed 2 and adjust the pot/knob up. I
tried that, starting from light kicks to pretty firm, but no luck.

Looking for suggestions on how to fix it.


Emailed reply

Ralph

The jackscrew motor is actually a pretty complex system, with two
relays , limit switches and whatnot controlling it. The pots on the
control head are rather problematic, check them first.

To find out if your motor is bad, pull the motor leads from the term
strips and hook a 3ph source to them for a second. I generally use a
relay for this btw.as the motor runs fast as hell. Reverse two leads
to back the screw off, as it will probably hit an end stop while
testing.

Ralph...quite frankly...the jackscrew drive is a bitch to work on, and
there were about 4 variations over the years.

.. If you are having problems with one...the best thing to do is pick
up a VFD that is rated for about 2hp, and raise the jackscrew to
about mid range, and use the VFD for motor control. Its easy to use
the drum switches for forward/reverse and start/stop,,,,,so you can
use your external levers. Change one of the current speed pots to the
VFD speed control pot and you are golden.

Buying and installing a VFD to run the spindle motor, will be
considerably cheaper than having a service tech out.

Gunner, 805-732-5308 cell anytime.