Spindle speed runs to high speed uncontrolled
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  1. #1
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    Default Spindle speed runs to high speed uncontrolled

    While doing some threading, my Hardinge HLV lathe spindle speed zoomed up to high without my doing anything unusual. Now, in turning or threading, I no loner can lower the speed, it is stuck at high. Any ideas on what to explore first would be appreciated. I assume it is an electrical issue but looking for ideas where to look first.

    Thanks in advance

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    Is this a machine with a push-button speed control? If so, carefully look for a stuck "High" switch or shorted wires somewhere.

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    This machine has the momentary rotary switch. When turned one way it gradually increases speed by moving the jack screw and turning it the other it does the opposite.

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    It's likely the switch or wiring. Look for shorts.

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    No obvious shorts. The Rotary switch was a bit wonky, but it seems to be fine after I tightened the connections on the back of same. Correct me if I am wrong; however, the jack screw motor is all the way at the bottom so the bottom micro-switch is closed, I assume that this is a normal state and if the machine was working properly the slow/faster switch should slow down the spindle, correct? Thanks. Very perplexing.

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    It's been ages (like, 30 years) since I worked with a Hardinge with power speed control (and that was a two-button affair for high and low adjustment), so I can't claim much more insight.

    With luck someone who knows your specific style of machine will chime in.

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    An HLV-H with the 2 button speed control can do something like this if the machine is moved to a new location and the phase is reversed(Your clue will be the spindle switch vave to be in reverse to make it run forward). It will become locked and you will have to turn the screw that controls the varidrive manually to unlock it. Not sure if you have moved the machine or had a had an electrical problem. First thing to try is manually moving the screw to unlock it.

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    To make things perfectly clear, attach a few pictures of the electrical box.

    There are switches underneath a black cam (12 or more in long).
    They act up after a while if somebody engages in brutal punishment by bang the speed/on/off lever too hard.

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    So, the machine is running the screw to high speed as soon as power is applied. It is not a problem with reversed wiring as the spindle runs correctly. I plan to disconnect the wires to the reversing switch which should prevent the speed-adjusting motor from running. If that motor runs, it is a problem in the contractor, I believe. I am having a cocktail now, so I shall report back tomorrow. Prob not a good idea to "play" after a Mai Tai!

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    I used to work on them too. If I remember right on the end of the screw there is a box with limit switches in there, maybe a stuck contact or I think it's a stuck solenoid in the electrical box. I used to use a plastic handled screw driver and push the relays up to locate the bad ones. I'm no electrician but I bet that's the issue. I am friends with Iverson Machinery in Chicago one of the only authorized Hardinge rebuilders left. I found this manual page 22 shows the mechanism. Also on page 24 there is a rod (A) with nuts you adjust for the limits the travel http://vintagemachinery.org/pubs/417/21058.pdf

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    Well, I removed the two wires to the reversing rotary switch and it made no difference. Clearly, power is being applied to the variable-speed drive-motor independently of the position of the rotary speed-switch and independently of the position of the spindle fast/slow lever. The reversing contactor and overload relay seem fine as does all the wiring. As soon as power is applied to the machine the variable-speed drive-motor that runs the jack screw all the way to high speed, as though the 240 volt wiring was reversed, which it is not. I am wondering if there is a way to further diagnose this by disconnecting the control wires to either the reversing contactor or some similar action. I have what appears to be an accurate wiring diagram (original to the machine) but it is not clear the position of these relays (normally open vs closed). The other action I could take is to disconnect the power to the control circuits that comes off of the spindle speed control. If I understand correctly, the spindle speed control must be in low or high speed for poser to be applied to the control circuits (wire #10). Any thoughts would be appreciated.

    Thanks

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    Check to see if one of the limit switches has failed.


    Sent from my iPhone using Tapatalk

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    Contactor spring failure? Or contacts welded (unlikely) Typically, the up/down contactors are a mechanically interlocked pair , has it seemed reluctant to go slower for a while? (Sticky up contactor)

    The micro switches only inhibit so a failure would not cause it to lock . Has a phase reversal has occurred: is the fwd/rev switch in the correct position when running fwd?

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    These are all excellent suggestions; however, I found the problem, now I have to figure out the best way forward. Turns out that the reversing contactor froze in the "faster" position driving the jack screw all the way to its limit (it is suppose to pop open when you release the rotary switch). So, I removed the cover from the contractor and found that the machine worked fine. For some reason the two black plastic parts that prevent both the fast- and slow-contractors from operating simultaneously appeared to be providing just enough resistance to "prevent" the fast contactor from releasing. I tried to lubricate this "preventer" assembly, but it did not provide any relief. I guess I could replace the assembly (parts 2MP and 2ML); however, that is a lot of work given all the wires and the tight space. Has anyone else experienced this?

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    Billtodd: Your post appeared just after my response below. I am using a rotary phase converter for my 3-phase (home shop) and I did experience what seemed like a hickup on that earlier in the day, which I can not explain. That said, the spindle was running correctly and right in the middle of threading it started to speed up. The contactor turned out to be the cause, and as explained below the mechanical interlock appears to be causing enough physical resistance that the contactor does not open when the slow/fast rotary switch is released. It works fine when the mechanical interlock is removed, which is probably not a good long-term solution.


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