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Re: Soft Start for Lathe?

Posted: Thu Apr 25, 2019 5:10 pm
by liveaboard
whateg0 wrote: Thu Apr 25, 2019 12:45 pm Is a GFCI breaker? I have a buddy who has GFCI on one wall and he can't start his mill without it tripping.

Dave
A friend of mine had a drill press; gfi would trip if you touched it while it was running.
So he put a thick rubber mat on the floor in front of it to stand on while using it.
Problem solved.

Re: Soft Start for Lathe?

Posted: Thu Apr 25, 2019 5:51 pm
by BadDog
I just checked mine, and with the main drive disengaged (gear head H/N/L in N), grabbing one jaw of an 8" chuck and giving it a firm (not hard) throw, I get more than 1.5 turns without trying hard.

But I don't believe your's is a clutch, nor is mine. You can't really compare a direct drive with a clutched spindle lathe in this respect, at least not as apples to apples (depending on clutch integration).

Re: Soft Start for Lathe?

Posted: Thu Apr 25, 2019 6:44 pm
by WesHowe
On a 4th of July weekend a few years ago, my house A/C quit cooling. A quick analysis showed it was because the outside unit (compressor) was not powered because the breaker popped. Reset the breaker, unit started and cool air returned. But after the unit stopped and tried to restart later, the breaker popped. After several rounds of this I called a repair company, and paid dearly for the holiday service.

Turns out the starter capacitor had burnt out. Due to it's functional absence, when the unit tried to start it drew a very high current very briefly. While an A/C is not a mill, they both have motors. The symptoms sound alike, may be worth checking into.

- Wes

Re: Soft Start for Lathe?

Posted: Thu Apr 25, 2019 9:27 pm
by David2011
BadDog wrote: Thu Apr 25, 2019 5:51 pm I just checked mine, and with the main drive disengaged (gear head H/N/L in N), grabbing one jaw of an 8" chuck and giving it a firm (not hard) throw, I get more than 1.5 turns without trying hard.

But I don't believe your's is a clutch, nor is mine. You can't really compare a direct drive with a clutched spindle lathe in this respect, at least not as apples to apples (depending on clutch integration).
I get a half turn with the tumbler disengaged and the belt off of the spindle pulley so will pursue that. I think with everything disconnected it should be pretty comparable.

Re: Soft Start for Lathe?

Posted: Thu Apr 25, 2019 9:30 pm
by David2011
WesHowe wrote: Thu Apr 25, 2019 6:44 pm On a 4th of July weekend a few years ago, my house A/C quit cooling. A quick analysis showed it was because the outside unit (compressor) was not powered because the breaker popped. Reset the breaker, unit started and cool air returned. But after the unit stopped and tried to restart later, the breaker popped. After several rounds of this I called a repair company, and paid dearly for the holiday service.

Turns out the starter capacitor had burnt out. Due to it's functional absence, when the unit tried to start it drew a very high current very briefly. While an A/C is not a mill, they both have motors. The symptoms sound alike, may be worth checking into.

- Wes
We had that happen as well, middle of the Summer on 105 degree day. It was the cap but nowhere to buy one. It was well worth the AC service man's after hours charge. An aging/failing capacitor did cross my mind and they aren't expensive. I should probably replace it just as a PM. It's 41 years old.

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 6:49 am
by RSG
For what it's worth, my new mill was giving me a problem on start up and doing the same thing, blowing the breaker. We (Electrician and I) eventually identified the issue to be a faulty cap start switch arcing. Once I replaced it and set it up properly I haven't had an issue again.

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 8:03 am
by John Hasler
David2011 wrote: Thu Apr 25, 2019 9:27 pm
BadDog wrote: Thu Apr 25, 2019 5:51 pm I just checked mine, and with the main drive disengaged (gear head H/N/L in N), grabbing one jaw of an 8" chuck and giving it a firm (not hard) throw, I get more than 1.5 turns without trying hard.

But I don't believe your's is a clutch, nor is mine. You can't really compare a direct drive with a clutched spindle lathe in this respect, at least not as apples to apples (depending on clutch integration).
I get a half turn with the tumbler disengaged and the belt off of the spindle pulley so will pursue that. I think with everything disconnected it should be pretty comparable.
That doesn't sound good. I think you should still check the starting capacitor, though. More than one thing can be wrong.

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 9:36 am
by SteveHGraham
I don't suppose you have the wrong start cap? A capacitor sucks a lot of juice when you hit the switch.

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 10:27 am
by John Hasler
Yes. An oversized starting cap would increase starting current.

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 12:51 pm
by Glenn Brooks
Generally the lathes I’ve worked on have a fairly free spinning chuck. Some of my old time lathes, with split bearings, sometimes actually stall the motor if I tighten the bearing caps down to much. Puts excessive pressure on the head stock shaft, and it binds up. Even then, I can’t recall a time when this popped the breaker.

You could try to pull the bearings, and check lubrication and wear. but if this is a gear head lathe, you will be probably looking at a major tear down and lots of trouble pressing the existing bearings out of the headstock casting. I went through this on my old, 1950 12” Standard Modern lathe years ago - a big heavy, old school industrial machine, with a 5 hp motor. Massive job, and at the end, found nothing at all wrong with the bearings. They were actually lubricated from the oil bath in the headstock.

The only other question to ask is: is this the original motor? If not, maybe some prior owner put an improperly sized replacement in the lathe - to small for the machine. 1 hp seems light if the gear train is as heavy as you describe.

Another idea, might be to just call Jet service center and see what they know them about this model lathe.

All in all, I think the easiest test to run would be if you replaced the breaker with a 30 amp breaker and made a bucket of chips at all speeds- see what happens. If you’ve got some kind of short going on, this likely would trip a 30 amp breaker as well. If all is well, maybe your initial thought that the existing 20a circuit is just to light for the motor, is the correct one.

Good luck. Let us know what happens.
Glenn

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 1:00 pm
by David2011
SteveHGraham wrote: Fri Apr 26, 2019 9:36 am I don't suppose you have the wrong start cap? A capacitor sucks a lot of juice when you hit the switch.
I know the history of this lathe since it was 4 years old and it's 41 years old now. I'm pretty sure the cap is original. Good because it would be the right size. Bad because it's 41 years old. I'm pretty sure capacitors dump electricity on starting; not draw it. (They can be used as batteries in some conditions.)

Re: Soft Start for Lathe?

Posted: Fri Apr 26, 2019 1:46 pm
by David2011
Glenn Brooks wrote: Fri Apr 26, 2019 12:51 pm Generally the lathes I’ve worked on have a fairly free spinning chuck. Some of my old time lathes, with split bearings, sometimes actually stall the motor if I tighten the bearing caps down to much. Puts excessive pressure on the head stock shaft, and it binds up. Even then, I can’t recall a time when this popped the breaker.

You could try to pull the bearings, and check lubrication and wear. but if this is a gear head lathe, you will be probably looking at a major tear down and lots of trouble pressing the existing bearings out of the headstock casting. I went through this on my old, 1950 12” Standard Modern lathe years ago - a big heavy, old school industrial machine, with a 5 hp motor. Massive job, and at the end, found nothing at all wrong with the bearings. They were actually lubricated from the oil bath in the headstock.

The only other question to ask is: is this the original motor? If not, maybe some prior owner put an improperly sized replacement in the lathe - to small for the machine. 1 hp seems light if the gear train is as heavy as you describe.

Another idea, might be to just call Jet service center and see what they know them about this model lathe.

All in all, I think the easiest test to run would be if you replaced the breaker with a 30 amp breaker and made a bucket of chips at all speeds- see what happens. If you’ve got some kind of short going on, this likely would trip a 30 amp breaker as well. If all is well, maybe your initial thought that the existing 20a circuit is just to light for the motor, is the correct one.

Good luck. Let us know what happens.
Glenn
I like your plan. Yes, it's a gearhead lathe. In spite of the small size in many ways it's built like much larger lathes. The spindle bearings are held in place with external caps so I don't think they would be pressed onto the spindle. I don't see how it could be installed with the bearings already on the spindle. Pretty sure the lathe has never been disassembled. The year on the motor is the same as the year of manufacture of the lathe and both are made in Taiwan. The original spec is for a 1 HP motor and I believe the belt was original when I got the machine. I can't guarantee it's the original motor but it has all the indicators of being original. The gearbox is run dry with grease applied to the gears. The bearings are lubed through fill caps on the front of the headstock and they have sight glasses for the oil level.

After looking at the bearing installation from the outside it appears that I could remove the caps and flush them out with a brake cleaner type aerosol without removing them. I have PDFs of the instructions and assembly along with parts lists.

I bought a 30A breaker some time ago but was reluctant to install it on a 12Ga circuit. Other comments indicate that it's not unsafe for a dedicated circuit so I'll find the breaker and install it.

Thanks!
David