Stop button issues on reverse direction

[Froneck]

I have a Hendey 14" lathe that works great having a 5hp 1200rpm motor (sync. speed) With my homemade RPC. All machines are wired so the made leg is connected to the motor via contacter terminal and all control wiring is connected to single phase supply. No issues if forward. Push start, motor starts as if connected to 3 phase. Push stop, contacter drops out and motor power removed! But if I start the motor in reverse, (works as it should) and push the stop button (same button for both directions, 3 push button switch) nothing happens. Eventually if I wobble the button while pushed in contacter will drop out. No big thing since I don't use reverse much but do when power tapping a hole.
Any idea as to why??? I'm quite familiar with forward/reverse contacter wiring! Understand how any why it's wired as it is thought I didn't wire it and contacter box in under the chip pan below the chuck making if difficult to trouble shoot. Nor is there an issue with other machines that have similar 3 button switch.

 

[rons]

Tighten down all screw connections.

 

[JST]

Stop usually breaks the circuit for the contactor coil, so a loose connection ought to have never started in the first place.

What concerns me is not that it does not stop right, but that it EVER stops at all! If there is an actual wiring error, it should do what it does all the time. So if it works eventually, then the issue is probably mechanical.

One possibility is that the reverse contactor has a sticky action, either literally a sticky pole piece, or the pole piece is magnetized (DC controls?) and does not easily release.

I think maybe sticky gunk on the pole piece, just because it does release, after the release spring has pulled on it for a while.

You are going to have to get into the box.

 

[Jraef]

It might also be an issue with the mechanical interlock between the contactors, that it is misaligned and jamming, or is worn out. So you are cutting power to the coil, but the mechanical interlock is not allowing the contactor to drop out. Not sure why wiggling the button would have an effect though, unless it’s just coincidental with the time it takes for the mechanical jam to work itself loose.

Simple test would be to disconnect the motor (for safety), energize the reverse function, then lift the wire off the coil. If it stays in, it’s a mechanical issue. If it drops out immediately, it’s an electrical one.