Import Lathe Contactor Questions 12x37

[StephenZ]

Hi everyone, Stephen here, new to the site. I've been searching through forums and found a few similar topics, but not the exact answers I was looking for. Here goes...I'm mechanically inclined, but not a professional electrician, so bear with me...
I picked up a barely used harbor freight 12x37 gap bed metal lathe last week. Ran it while i was there, the owner was really helpful and knowledgable...(meaning, I don't think anything was suspect). Anyway, once I got it home and mounted on a stand, I ran it a couple times while figuring out all the levers and whatnot. (I'm stepping up from a small 7x12 lathe, btw) I'm not sure if I switched something out of order, or something, but it suddenly didn't want to run anymore. Here are the symptoms:
-Power light comes on when switch is turned.
-Spindle doesn't respond to F or R lever, but I hear one of the contactors click.
-I found that the Fwd and Rev contactors will work if I manually press the mag plunger.
-The clicking when using the direction lever is the first contactor...whatever that one is called...not a direction one. when I switch to fwd or rev, it releases its magnetic hold and nothing happens. If I leave the lever engaged and manually press the contactor, the spindle will go perfectly.
So, I guess I'm asking for advice on what my likely culprits are.
The CN-11 contactor?
Did it just happen to give up its mag hold?
The motor jumps to life quickly when I push the contactor, so would that make the motor fine?
Direction switches? They seem ok, pretty basic switches..
The thermal protector?
Sorry for the essay...Thanks for any advice.
-Stephen

 

[TonyM]

Don't know what that specific machine has in the way of safety switches. If there are any check they are engaged maybe on chuck guard or drive guard.

 

[RM-MN]

I found a manual for that lathe or similar. The problem might be a safety interlock or you may need a new contactor (relay).

https://manualzz.com/doc/3201707/harbor-freight-tools-43681-user-s-manual

 

[StephenZ]

Thanks for the responses, guys. So, there aren't any safety switches that I could find...or find in the manual/online anywhere. Damn. Strangely, before work this morning, I fiddled around with it some more and it randomly started working in reverse only. I switched the reverse and forward trigger wires coming from the main relay/contactor and it worked in forward. Tonight, it didn't want to work again....then it did a little bit...so I switched wires back again, to test it and it stopped working at all...that's where I'm at now.. The main contactor/relay seems to start buzzing while I'm switching the direction lever back and forth...I just ordered a new CU-11 contactor to replace this one...I hate throwing parts at it, but I'm not sure what else to do...since it worked randomly a couple times, it seems like maybe an electrical component is losing the big fight...the main relay seems likely? Thanks again, everyone.
-Stephen Z

Edit: I read somewhere that the CU-11 is a replacement for the CN-11...they look to be the same (minus the auxillary contactor on the CU in my pic...) specs the same, too.. Thoughts?

 

[Wizard69]

Thanks for the responses, guys. So, there aren't any safety switches that I could find...or find in the manual/online anywhere. Damn. Strangely, before work this morning, I fiddled around with it some more and it randomly started working in reverse only. I switched the reverse and forward trigger wires coming from the main relay/contactor and it worked in forward. Tonight, it didn't want to work again....then it did a little bit...so I switched wires back again, to test it and it stopped working at all...that's where I'm at now.. The main contactor/relay seems to start buzzing while I'm switching the direction lever back and forth...I just ordered a new CU-11 contactor to replace this one...I hate throwing parts at it, but I'm not sure what else to do...since it worked randomly a couple times, it seems like maybe an electrical component is losing the big fight...the main relay seems likely? Thanks again, everyone.
-Stephen Z

Edit: I read somewhere that the CU-11 is a replacement for the CN-11...they look to be the same (minus the auxillary contactor on the CU in my pic...) specs the same, too.. Thoughts?

It kinda sounds like there is an external switch causing you issues. possibly an over travel to the saddle? Unless you have a accurate electrical diagram you are basically shooting in the dark. It is very difficult to do diagnostic work over the net plus I don't want you to end up dead. To that end you might want to try finding somebody locally with a bit of an electrical background.

By the way, during machine tool moves there is a very high probability of something getting damaged electrically. As always a close visual inspection is the first order of business.

 

[StephenZ]

It kinda sounds like there is an external switch causing you issues. possibly an over travel to the saddle? Unless you have a accurate electrical diagram you are basically shooting in the dark. It is very difficult to do diagnostic work over the net plus I don't want you to end up dead. To that end you might want to try finding somebody locally with a bit of an electrical background.

By the way, during machine tool moves there is a very high probability of something getting damaged electrically. As always a close visual inspection is the first order of business.

I have general diagrams of the machine and other similar ones. I can't find any indication of safety switches or anything that would de-energize the contactor when the spindle direction is selected...but, yes, I would not be surprised if there was some kind of damage during transport. I had to use my trailer to haul it 15 miles or so...CA roads...not good.
I also appreciate you not wanting me to end up dead.... I'd like to keep going for a bit longer, too... I'm a general contractor and have wired many homes, and restored several cars, I just haven't worked with lathe wiring and the use of multiple contactors, etc... I'm not saying I'm a pro, by any means, (I actually can't stand doing electrical) but I've been bitten a few times in my youth and will definitely be very careful..

 

[Anatol]

Coincidentally, I just posted a wiring diagram on this thread
https://www.homemodelenginemachinis...-12x36-lathe-wireing.22761/page-2#post-314705
Its an older model but similar (?) Hope its helpful.
If you can't find a correct and readable circuit diagram, you just have to make your own, can't really proceed without it. Tedious but useful long term. As often and not its a bad connection. Check continuity. Any sign of corrosion? I'd check any remote switches, as suggested. If you find corrosion at contacts, cut wires and reconnect. For hard to get to contacts (ie in contactor) theres an expensive but magical contact cleaner called deoxit.
BTW, a contactor is electromagnetic (a big relay), no permanent magnet, afaik.

 

[StephenZ]

Coincidentally, I just posted a wiring diagram on this thread
https://www.homemodelenginemachinis...-12x36-lathe-wireing.22761/page-2#post-314705
Its an older model but similar (?) Hope its helpful.
If you can't find a correct and readable circuit diagram, you just have to make your own, can't really proceed without it. Tedious but useful long term. As often and not its a bad connection. Check continuity. Any sign of corrosion? I'd check any remote switches, as suggested. If you find corrosion at contacts, cut wires and reconnect. For hard to get to contacts (ie in contactor) theres an expensive but magical contact cleaner called deoxit.
BTW, a contactor is electromagnetic (a big relay), no permanent magnet, afaik.

Yes! thank you. I saw your post there, too. I had asked advice on that thread, too, since it was so similar to my issues and was on the same lathe. I think the fact that the diagram is older, is actually perfect. My machine is probably 10-12 years old, so the tech seems to match it. Thank you!

 

[Brian Lawson]

Hi everyone, Stephen here, new to the site. I've been searching through forums and found a few similar topics, but not the exact answers I was looking for. Here goes...I'm mechanically inclined, but not a professional electrician, so bear with me...
I picked up a barely used harbor freight 12x37 gap bed metal lathe last week. Ran it while i was there, the owner was really helpful and knowledgable...(meaning, I don't think anything was suspect). Anyway, once I got it home and mounted on a stand, I ran it a couple times while figuring out all the levers and whatnot. (I'm stepping up from a small 7x12 lathe, btw) I'm not sure if I switched something out of order, or something, but it suddenly didn't want to run anymore. Here are the symptoms:
-Power light comes on when switch is turned.
-Spindle doesn't respond to F or R lever, but I hear one of the contactors click.
-I found that the Fwd and Rev contactors will work if I manually press the mag plunger.
-The clicking when using the direction lever is the first contactor...whatever that one is called...not a direction one. when I switch to fwd or rev, it releases its magnetic hold and nothing happens. If I leave the lever engaged and manually press the contactor, the spindle will go perfectly.
So, I guess I'm asking for advice on what my likely culprits are.
The CN-11 contactor?
Did it just happen to give up its mag hold?
The motor jumps to life quickly when I push the contactor, so would that make the motor fine?
Direction switches? They seem ok, pretty basic switches..
The thermal protector?
Sorry for the essay...Thanks for any advice.
-Stephen
View attachment 104547

 

[Brian Lawson]

One thing that has not been mentioned, in either this thread or in the other recent thread, has to do with any common FWD-REV contactors/relays is that they generally will have an NC (normally closed contact) in series with the "opposite direction" contactor. That is, each has a "back contact" that stops the "other contactor" from pulling in if that contact is "open". On larger equipment, there is normally also a mechanical interlock.
I see that someone has also mentioned a safety switch on the "change gear cover", and on larger lathes, there is a switch that stops motion if the foot brake is applied.

It is difficult in the photos to "see" how the wiring is terminated at each connection. If "stakon" crimp terminals were used, and they are NOT made by T&B, then they have a bad habit of cracking but then "laying" in place, so that they will have go/no-go state, depending on who may have just sneezed!! Very tough to diagnose and find. Give EVERY wire a slight "tug" to see if they are still OK, and not either broken or loose.

Also note that the "drawing(s)" submitted show the lathe to be 220VAC single phase. Some where on the drawings, there should be "overloads" provided, and on one I think I saw the term "heater", which is probably the overloads.

Good luck.

Brian Lawson, Bothwell, Ontario.

 

[StephenZ]

One thing that has not been mentioned, in either this thread or in the other recent thread, has to do with any common FWD-REV contactors/relays is that they generally will have an NC (normally closed contact) in series with the "opposite direction" contactor. That is, each has a "back contact" that stops the "other contactor" from pulling in if that contact is "open". On larger equipment, there is normally also a mechanical interlock.
I see that someone has also mentioned a safety switch on the "change gear cover", and on larger lathes, there is a switch that stops motion if the foot brake is applied.

It is difficult in the photos to "see" how the wiring is terminated at each connection. If "stakon" crimp terminals were used, and they are NOT made by T&B, then they have a bad habit of cracking but then "laying" in place, so that they will have go/no-go state, depending on who may have just sneezed!! Very tough to diagnose and find. Give EVERY wire a slight "tug" to see if they are still OK, and not either broken or loose.

Also note that the "drawing(s)" submitted show the lathe to be 220VAC single phase. Some where on the drawings, there should be "overloads" provided, and on one I think I saw the term "heater", which is probably the overloads.

Good luck.

Brian Lawson, Bothwell, Ontario.

Yes, all good bits of info. I wish there were some sort of safety switch that I just didn't see, but I've been over every inch of this thing and see nothing...kind of odd, really. Yeah, I hear you about those crimp on connectors. I have tugged on each one and checked their set screws, too. Always good practice!
Yes, 220v single phase. It has a thermal overload that seems to be functioning properly. I traced the current through it in on and off positions and tested the breaker feature of it. It popped and reset fine. That should be good, right?

 

[DJP]

Back up one more device and test the L1 and L2 fuses/breakers in your panel box. I have seen strange things happen when one side of the line voltage is missing or weak.

 

[StephenZ]

Back up one more device and test the L1 and L2 fuses/breakers in your panel box. I have seen strange things happen when one side of the line voltage is missing or weak.

Funny, you say that. I was standing next to the plug this morning and thought the same thing. Ran it back to the sub panel I had installed...all good.

 

[Wizard69]

Funny, you say that. I was standing next to the plug this morning and thought the same thing. Ran it back to the sub panel I had installed...all good.

I tried looking at the photo you posted with respect to the relay you think is a problem. The first problem to resolve is are you changing directions with the motor stopped? The forward and revers should be electrically interlocked to prevent that and likely mechanically interlocked.

As for the relay in question what do you mean by pops out? Is the relay shutting off or does it have some sort of overload function. (I can’t see from the picture what it really does in the circuit). Normally when I hear the word pop, I think breaker or overload device that needs to be reset. This may sound picky but it helps to understand what you have happening here. At the moment I believe that the switching of motor direction is purposefully shutting off this relay.

I could be wrong there but at this point to go further would require ringing out the electrical system.

Also you mentioned single phase operation. Frankly it has been so long I’ve forgotten how that is done with relays on a single phase system.

Lastly there are a number of cables leaving that panel box, the must go someplace.

 

[StephenZ]

I tried looking at the photo you posted with respect to the relay you think is a problem. The first problem to resolve is are you changing directions with the motor stopped? The forward and revers should be electrically interlocked to prevent that and likely mechanically interlocked.

As for the relay in question what do you mean by pops out? Is the relay shutting off or does it have some sort of overload function. (I can’t see from the picture what it really does in the circuit). Normally when I hear the word pop, I think breaker or overload device that needs to be reset. This may sound picky but it helps to understand what you have happening here. At the moment I believe that the switching of motor direction is purposefully shutting off this relay.

I could be wrong there but at this point to go further would require ringing out the electrical system.

Also you mentioned single phase operation. Frankly it has been so long I’ve forgotten how that is done with relays on a single phase system.

Lastly there are a number of cables leaving that panel box, the must go someplace.

Ah, yes, sorry, poor choice of descriptives. The ‘pop’, I meant to describe the de-energizing of the magnetic contractor. When power is on to the machine, that first relay/contactor pulls in and should stay, I believe. When a spindle direction is chosen, that contactor de-energizes and nothing moves. I believe the contactor is going bad and can’t hold when the spindle direction is chosen.
And, no, I never would try changing direction when the is motor moving.
I’ve also run down all the wires in the machine to their destinations and figured the purpose and currents of them. Definitely nothing going to any safety interlock anything.
Short of something else I’ve missed, I’m fairly certain it has to do with something in the contactor/transformer area. Of course, I’m waiting for my new green power light/holy grail of electrical circuits before I can do anything else...lol.
Thank you for your help!

 

[StephenZ]

I tried looking at the photo you posted with respect to the relay you think is a problem. The first problem to resolve is are you changing directions with the motor stopped? The forward and revers should be electrically interlocked to prevent that and likely mechanically interlocked.
At the moment I believe that the switching of motor direction is purposefully shutting off this relay.

Interesting. Even if I’m switching properly, something in that direction switch-main relay/contactor-the direction contactors may be de-energizing that relay? The direction switches go through that first main relay/contactor, so would that further implicate that relay as the failure? That’s where the ‘buck’ seems to be stopping with all the wire tracing I’ve done..

 

[DJP]

If you are convinced that the relay is faulty bypass it with a suitable test lead and see if the machine runs as intended. You can build a test lead with a breaker in the line in case there is a short. I have one with a 10 amp breaker just for this testing process. Isolating the failed component is the objective. Replacing it with a known good part is the next step.

 

[Cogsy]

I'm not much of an electrical guy (to put it mildly) but I just remembered back when I had an issue with one of the capacitors on my lathe motor. The first sign was the magnetic contactor 'playing up' and struggling to stay engaged. Sometimes it would, sometimes it wouldn't, then the cap blew and once I replaced it all was good. Not saying it's your issue, just mentioning it as I remembered it.

 

[StephenZ]

I'm not much of an electrical guy (to put it mildly) but I just remembered back when I had an issue with one of the capacitors on my lathe motor. The first sign was the magnetic contactor 'playing up' and struggling to stay engaged. Sometimes it would, sometimes it wouldn't, then the cap blew and once I replaced it all was good. Not saying it's your issue, just mentioning it as I remembered it.

Ah, the motor caps.. when that happened, were you still able to manually engage the contactor and run the motor? When my contactor de energizes, I can push it back in and hold it and the motor fires right up immediately.

 

[ignator]

Hi everyone, Stephen here, new to the site. I've been searching through forums and found a few similar topics, but not the exact answers I was looking for. Here goes...I'm mechanically inclined, but not a professional electrician, so bear with me...
I picked up a barely used harbor freight 12x37 gap bed metal lathe last week. Ran it while i was there, the owner was really helpful and knowledgable...(meaning, I don't think anything was suspect). Anyway, once I got it home and mounted on a stand, I ran it a couple times while figuring out all the levers and whatnot. (I'm stepping up from a small 7x12 lathe, btw) I'm not sure if I switched something out of order, or something, but it suddenly didn't want to run anymore. Here are the symptoms:
-Power light comes on when switch is turned.
-Spindle doesn't respond to F or R lever, but I hear one of the contactors click.
-I found that the Fwd and Rev contactors will work if I manually press the mag plunger.
-The clicking when using the direction lever is the first contactor...whatever that one is called...not a direction one. when I switch to fwd or rev, it releases its magnetic hold and nothing happens. If I leave the lever engaged and manually press the contactor, the spindle will go perfectly.
So, I guess I'm asking for advice on what my likely culprits are.
The CN-11 contactor?
Did it just happen to give up its mag hold?
The motor jumps to life quickly when I push the contactor, so would that make the motor fine?
Direction switches? They seem ok, pretty basic switches..
The thermal protector?
Sorry for the essay...Thanks for any advice.
-Stephen
View attachment 104547

I'm going to assume that the correct schematic is the one RM-MN posted a link to, as this was a direct HF. If you have an HF model number that should be included in your post.
I suspect it is the KA contact that has failed open. This is a safety inter lock to require the FWD-RVR selector to be in the off position. It latches up this interlock by applying power to the KA relay coil when the FWD-RVR selector is off.
Your bypassing all this when you manually engage the motor by closing the KM1 or KM2 motor contactors.
Your motor is not the issue if it starts up by manually pressing the KM1/KM2 magnetic switches.
You need a voltage ohm meter and with the power plug removed, check the KA contact that is pointed at in the below schematic. If the meter reading (in ohms mode) shows low ohms, when you manually close it, then check for loose wiring. If no issue found, then power the machine up and use the volt meter set to measure low AC volts, for the control transformer output. Note the one side that shows 0 (zero) that is a common, connect that one lead to your volt meter. The other lead connect to the KA magnetic coil terminal, and see if it shows voltage when you move the direction selector into FWD or RVR. If not, follow the wiring to the source of why it's open.
In the below schematic, where I have "these KA contacts open...." is not supposed to happen when the direction is selected, your indicating this as a problem, that from my limited input, indicates the KA holding contact is not in the circuit from either it's failure of wiring problem. Note that when no direction is selected the SA1 and SA2 direction switches provide power to the KA coil. You indicate you hear this close.
The FR and it's switch contact appear to be OK, this is the motor overload. Everything would be off if the FR switch was open.
I don't know what the SA3 or SB1 is about, does your machine have a foot brake? Then one of these switches is to shut motor power off when used.
HL is your power on indicator light, you indicate it's on, so I think messing with this is the wrong path.

But if this is not the schematic to your machine, then all this becomes moot.