Hardinge HC spindle variable speed won't change speed

I need some help with the variable speed on my Hardinge HC lathe. It will not change speed, up or down. It works
in speed range 1 and 2 but shows no change when shifting to speed range 3. This problem started as an intermittent
problem, coming and going for a few months. Now it seems to have failed completely. It did run for a number of years
with no problem. The power is from a rotary phase convertor but that has all been in place for 15 years and
nothing has been changed. Other machines are operating as normal so I don't think it is the power.

The machine is from some time in the 60's and has rounded corner sheet metal. Here is what has been done so far.
The numbered wires have been checked for continuity from the control panel to the main electrical box and on to
the speed change motor control under the headstock. The speed control pots have been cleaned and checked, they
show a variable resistance across the full range and look good. Same for the pot at the speed change motor which
seems to be used for a sense circuit? The transistors in the control box were "diode" checked and seem OK. They
were also put back in the opposite socket but no change was seen. All screws on the ring lugs on the wiring were
loosened and re-tightened. The two P&B relays in the main electrical cabinet were swapped with no change shown.
There is 30VDC coming from the power supply near the P&B relays and the caps in the power supply have been tested
and are good. The micro switches on the drum switches were all checked and appear to be good. The speed it is going
to is in the normal range and is not tripping the over travel micro switches at each end of the speed range.

Another big clue is that with the motor turned off if I turn the large speed adjust screw by hand the RPM's go up or
down but it always returns the speed to the same spot. If I manually actuate the contactors for raising or lowering
the RPM's the speed will change but again, it always returns to the same speed. And range three doesn't work at all.

I have an HC manual on CD but that doesn't help much for this problem. There is also a blue print electrical
diagram that was in the main electrical cabinet. That is very hard to read and some parts are not legible.

What I need is some direction on where to look and what I should expect to find. Thanks in advance for any good
ideas on how to proceed.

John Mc Cabe

You have done a lot of troubleshooting and have not left many obvious things to check. The third speed is not working at all? Does it die when shifted to that position? Could be a contact in the drum switch? I do not know if that would affect the varidrive or not. When you are moving the screw by actuating the contactors, you are doing this with the spindle motor running? Varidrives do not like speed changes while not running. That is the only reason I could think of that it would move back to the original RPM. It has been 35 years since I have run an original hardinge chucker. We have a Tsugami copy but it is a different animal. The cams on it bring it back to a preset speed completely different than the original Hardinge.

When I shift to the third speed the spindle continues to run at the same speed as when it is in position two. There isn't any change, not even a hesitation. We also checked the drum switch and all of the switches turn on and off. When changing the spindle speed with the contactor the spindle is running. You are correct the varidrive does not like that and returns to the speed it was running at. That makes me think that at least some of the system is working. I just don't know what makes it home in on that speed. If I can find that out I will know where to look next.

There is a rod that actuates the limit switches, could it be off center and dragging on the side of the limit switches? Is what brings the speed back mechanical or electrical? Disconect the varidrive motor and find out?
It has been too long but I am thinking the HC had some kind of memory on the 2 to 3 change. The 2 and 3 speeds were set independantly with the speed control switch I think. The hardinges were too dependable I never had much reason to go into the cabinet, the Tsugamis you had to open them up to set the speed cams everytime your job required different speeds. Sorry I could not be more help.

Hardinge HC Chucker

Hi John,

I had an issue with my HC Chucker a while back. There were a series of reset buttons near the bottom of the cabinet. I pressed all of them to make sure they were not disconnected and that fixed my issue. Don't know if that could be your problem but might be worth a try.

I'm out of town all this week. I'll have take another look at the limit switches and see if there is anything else mechanical like a rod that I might have missed. I don't recall any reset switches but will look for those as well. I'll let you know what I find after I return home. Thanks for the suggestions.

Now that I am home again I took another look at the items suggested above. I looked at the rods that connect the levers to the drum switches. They seem to be OK. The drum switches and the limit switches have all been checked and turn on and off. When changing the speed lever from position 2 to position 3 there is no change of speed. If I move the speed adjust screw when power is off, the speed change motor moves the nut back to the same position when I power back up. I can see and hear the up speed and down speed contactors actuating so that is why I think the problem is electrical in nature. Once I opened the electrical cabinet I found the reset buttons. They seem like a circuit breaker? I pushed each one and started it up but found no change. I then pressed each one with power on and the spindle turning, still no change. I did not notice any resistance or any mechanical change like when a circuit breaker is reset. I need to find someone that understands the electrical circuit and could give me a suggestion on what to look for there. I don't know for sure but would suspect that the HC has the same circuit as the HLV does anyone know if that is correct? Thanks for all the suggestion so far.

Now that I am home again I took another look at the items suggested above. I looked at the rods that connect the levers to the drum switches. They seem to be OK. The drum switches and the limit switches have all been checked and turn on and off. When changing the speed lever from position 2 to position 3 there is no change of speed. If I move the speed adjust screw when power is off, the speed change motor moves the nut back to the same position when I power back up. I can see and hear the up speed and down speed contactors actuating so that is why I think the problem is electrical in nature. Once I opened the electrical cabinet I found the reset buttons. They seem like a circuit breaker? I pushed each one and started it up but found no change. I then pressed each one with power on and the spindle turning, still no change. I did not notice any resistance or any mechanical change like when a circuit breaker is reset. I need to find someone that understands the electrical circuit and could give me a suggestion on what to look for there. I don't know for sure but would suspect that the HC has the same circuit as the HLV does anyone know if that is correct? Thanks for all the suggestion so far.

It has been more than 30 years since I ran an HC, but I seem to remember that the speed 2 and speed 3 were independant of each other. I have a funtioning Tsugami copy on the HC but it's speed selection on the 2-3 shift is made with cams. I think the HC used 2 independant circuits so it could "remember" the speeds selected.
The HLV-h does not change speeds with the varidrive when the speed lever is operated, just the motor speed is changed. Probably many of the parts are the same but some additional electrical or mechanical parts parts were probably used in the HC.
When you change the number 2 speed does the #3 speed always stay the same or does it follow the #2 speed?
The answer to this question will give you a clue to the problem.

On the HC there are 2 speed adjust pots on the control head. One covers the speed setting for position 1 and 2 of the speed selection lever. The other pot is for speed 3. When moving the lever from position 2 to position 3 there is no change of speed. Moving either pot shows no speed change at all. That is part of the reason I think the problem is electrical in nature. The pots check out OK for resistance and change from high to low across their range. I am aware that the HLV only has low and high speed but I have to wonder if the circuit for the speed change isn't similar. After all they are both using a remotely controlled motor to turn a screw to change the position of a belt on a 2 piece pulley. The speed adjust motor always returns the screw to the same position. If I turn off the spindle and turn the speed adjust screw by hand in either direction, it always returns to the same place when the spindle is started again. The speed adjust circuit is working to some degree. I just don't understand how it works. That circuit is where I thinks the problem is and what I need help with.

If adjusting either or both pots changes nothing, I would look at the circuit controled by the pots. Maybe this is down stream, between the pots and the varidrive motor. Also it seems like the speed control needs feedback from the pulley positions to know how far the motor should go? Is the feedback working (maybe a mechanical link)?

I was wondering if you ever solved this? I have a chucker with the same problem. Speed control pots do nothing and no speed change from 2-3. Also buzzing contactor in speed 1 but it does switch speeds

Exact same issue

Did either of you resolve this issue. I have an HC doing the exact same thing.

Bob J

MitsTech said:

I was wondering if you ever solved this? I have a chucker with the same problem. Speed control pots do nothing and no speed change from 2-3. Also buzzing contactor in speed 1 but it does switch speeds

Click to expand...

You have picked up a very old thread.
You would have better luck starting your own thread with a good description of what your problem is.

Bill