Lathe not working...again...

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ChrisD123

Member
Joined
Jun 11, 2012
Messages
167
Location
Calgary, Alberta, Canada
Hey guys, so yesterday I was just finishing up a pen when my lathes motor seemed to have let go. It would start fluxuating in speed and then shut off, and it wouldn't really start unless I turned the chuck while hitting the start button. Even this did not keep it going it didn't want to stay running, this has happened before and I somehow fixed it but I have no idea what wrong. It's still getting power and I've plugged it straight into the wall so it's not a power problems, does anyone have an ideas on fixing this?
 
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Sounds to me like a problem with the motor, either motor going bad or a bad connection not providing enough power to the motor. But maybe someone else would have different thoughts.
 
have you checked the switch? i have heard of really fine dust getting into the switch and causing a problem with the connection. You could also bypass the switch to rule that part out
 
Does the motor have a capacitor on it? If it is a Start/Run Capacitor it could be going bad. Be careful if you do when you go look at it, it stores a charge and packs a hell of a punch if you cross the phases.
 
Ummm I'm not sure where that would be there's a rotation switch. Speed switch. On off switch. Fuse thing and that's it on the main board. Last time I cleanedy lathe though I think I pulled out the bushing and they shocked me... Haha not fun! Would that be what ur talking about?
 
That happened to my jet 1220 so I called jet and they sent me the capacitor replaced it myself and has been working great since then.
 
If that's the lathe I think it is it is about the same as the other metal mini lathes (variable speed DC motor mini lathes from Grizzly, HF, etc.).

Several things to check beginning with the switches and the connectors for the wiring to see if they are loose or corroded, maybe the motor brushes if you have significant time on it, and maybe the most likely being the speed control potentiometer if the others check out (which can cause erratic speed and operation of the motor).

Those little fuse holders can also cause trouble - simple as they are there is nothing the Chinese cannot make poorly.

If all those check out and obvious things like the electric line(s) are good and the wall outlet good then the problem may lie with your motor controller itself (that would be the circuit board). Several problems with those boards (if they are the same as the Grizzly, HF, etc. boards) are the MOSFETS and sometimes bad solder connections. There are other things that can cause the problem such as the rectifier circuit in them (which can be found with a simple multimeter to see if it is putting out AC or DC voltage) but not as common. They're pretty easy to fix if you can do simple electronic soldering to replace the defective parts.


If you trouble shoot inside the controller box with the cover off do yourself a favor and unplug it first then put it all the way back together before plugging it back in, even the DC side has over a hundred volts which can give a fairly stiff shock. It takes a little longer that way but is much safer.
 
ChrisD123 said:
Hey guys, so yesterday I was just finishing up a pen when my lathes motor seemed to have let go. It would start fluxuating in speed and then shut off, and it wouldn't really start unless I turned the chuck while hitting the start button. Even this did not keep it going it didn't want to stay running, this has happened before and I somehow fixed it but I have no idea what wrong. It's still getting power and I've plugged it straight into the wall so it's not a power problems, does anyone have an ideas on fixing this?
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I have 2 mini 7" metal lathes this sounds very familiar. A few things comes to mind first BRUSHES how much time do have on your lathe. I had to replace my brushes after about 2 years (I had heavy use) Another weak spot is the F.O.R. switch if you don't have a dust cap on your toggle switch dust gets in and destroys your switch I have been through 3 of those.
But with this statement fluxuating in speed and then shut off my bet would be brushes. You don't have to pull the motor to get to them. Look under your ways near your head stock you will see the access hole for near brush (the other is on opposite side) You should be able to unscrew the plastic cap and pull your brush out if it has any burnt look to it or if it's less then say 1/4" (don't have specs) also look at the spring (I had one break once) If it is worn down to say a 1/4" a quick fix would be to pull the spring just a bit to give the brush more tension. Then order new brushes.

JMOP good luck
Bruce
 
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ChrisD123 said:
hey guys! thanks for all the help! after checking it out further i found that the brushes on the back had a broken spring and wernt contacting properly, i fixed it and now all it sounds thank again for all the help!
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Yep had that happen to me. NOW is the time to order new brushes.

AND if your lathe doesn't have a rubber boot on the F.O.R. switch (new ones do, older ones do not) I would get one and keep the dust out of the switch or that will next. Typically metal lathes doesn't encounter the fine dust we tend to make.

Good luck
 
ChrisD123 said:
hey guys! thanks for all the help! after checking it out further i found that the brushes on the back had a broken spring and wernt contacting properly, i fixed it and now all it sounds thank again for all the help!
Click to expand...

Make sure to install the brushes the same way they came out, same side and same up/down orientation. This ensures the brushes seat the same way.
 
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