Myford ML7 stalling under load

[gaz1]

Thanks for all the replies. Sorry Gaz I wasn't quit following what you meant.
No, the belts aren't slipping as far as I can tell. When sufficient load is placed on the work piece, the motor slows down and the chuck will eventually stall. Once it's stalled everything speeds up again and keeps spinning. So where could it be slipping?
It's a Bernerd chuck I believe.

Unfortunately I can't take a look at it until next weekend. The pic attached is the best I can do until then.

View attachment 372404

yours is a 2 belt from the motor so does suffer from belt slip as you enguage and disenguage ( clutch ) the belt to the head stock

you also have a backplate before you get to the chuck

if you look at your pic alone the spindle is all one piece to a degree if that piece was spinning as you said and the backplate or chuck wasnt then you have an issue with the backplate chuck area

if that spindle wasnt spinning and the belt pulley was spinning then you have an issue with the pin that connects the spindle to the belt drive system

theres only 2 ways i can think of to stall a motor out

motor not strong enough to spin
or
too deep of a cut is being taken

 

[tigdlo]

Thanks for all the replies. Sorry Gaz I wasn't quit following what you meant.
No, the belts aren't slipping as far as I can tell. When sufficient load is placed on the work piece, the motor slows down and the chuck will eventually stall. Once it's stalled everything speeds up again and keeps spinning. So where could it be slipping?
It's a Bernerd chuck I believe.

Unfortunately I can't take a look at it until next weekend. The pic attached is the best I can do until then.

View attachment 372404

Are you drilling a 12mm hole or cutting a taper with a taper reamer as in the photo? If it's the taper I don't think you have the power/torque to do it and would be better using your topslide and cleaning it up by hand with the reamer.

 

[hooblah]

Old pic. I can't get to the lathe until at least next weekend. The reamer worked fine.

 

[hooblah]

I'm pretty sure the backplate is not spinning with the chuck stationary. Is that what some of you are hinting at? How does that even work?

 

[brightspark]

I'm pretty sure the backplate is not spinning with the chuck stationary. Is that what some of you are hinting at? How does that even work?

the backplate is screwed on to the spindle and the chuck bolted to it

 

[hooblah]

Yes, so how is it possible for the backplate to spin but not the chuck? Perhaps I'm getting confused, but that's what it's reading like.

 

[minimutly]

Lads lads lads. This is almost as bad as the Yamaha xj forum (Americans mostly), where people are flat out typing at keyboards trying to diagnose someone’s xyz issue from the internet, when the answer is for the OP to just have a close look at it. By all means carry on, if it floats your boat, but it is all a bit silly no?

 

[gaz1]

either this whole piece is spinning or its not the rght side being your threaded end for the backplate to screw too



this is what it looks like without the bull gear and the 3 belts drive system within it

 

[brightspark]

either this whole piece is spinning or its not the rght side being your threaded end for the backplate to screw too

View attachment 372502

this is what it looks like without the bull gear and the 3 belts drive system within it

View attachment 372503

the small gear is fixed to the 3 step pulley. if the locking pin is engaged on the large right hand pulley the shaft is solid rel;ease the pin and it runs in back gear when that right hand lever with the bobble on is engaged. this explains it easier

 

[not done it yet]

What concerned me was that the OP said the motor slowed. The chuck would ‘stall’ (stop) if the motor stopped?

Makes me wonder if the OP is describing what actually occurs. Motor should be running at 1425rpm (or close to it) and not ‘slowing down’ at all loads less than over-load/.

 

[hooblah]

Ok let's try again...

Under excessive load, everything comes to a stop. Sometimes this is instantaneous, other times it's a gradual stop, with the motor losing rpm. This has only happened when I've been drilling using the tailstock.

Once the chuck stops, the motor speeds up to normal running speed, along with the belts and pulleys. There is no slipping of the belts as far as I can tell.

Once I back off the tool that's buried itself into the work piece, everything carries on as normal... Until the process repeats itself 2 secs later.

So if the shaft is solid, the pulleys are spinning, yet the backplate isn't... Sounds like (though I can't be sure until I look) the pulleys are spinning on the shaft. How are they secured to it?

 

[Pete.]

Once the chuck stops, the motor speeds up to normal running speed, along with the belts and pulleys. There is no slipping of the belts as far as I can tell.

Once I back off the tool that's buried itself into the work piece, everything carries on as normal... Until the process repeats itself 2 secs later.

So if the shaft is solid, the pulleys are spinning, yet the backplate isn't... Sounds like (though I can't be sure until I look) the pulleys are spinning on the shaft. How are they secured to it?

The pulleys are not fixed tot he shaft, they only connect to the spindle via the back gear or the bull gear pin.

Question: When the chuck stops turning but the motor and pulleys carry on, does the large gear behind the chuck (the bull gear) turn with the pulleys or stop with the chuck?

If it turns with the pulleys then the bull gear is slipping on the spindle.
If it stops with the chuck then the bull gear pin is not engaging.

 

[roofman]

Thanks for all the replies. Sorry Gaz I wasn't quit following what you meant.
No, the belts aren't slipping as far as I can tell. When sufficient load is placed on the work piece, the motor slows down and the chuck will eventually stall. Once it's stalled everything speeds up again and keeps spinning. So where could it be slipping?
It's a Bernerd chuck I believe.

Unfortunately I can't take a look at it until next weekend. The pic attached is the best I can do until then.

View attachment 372404

Dont think people are reading this correctly....sounds like a bad motor until it speeds up again..bit confused myself tbh

 

[Scalarocco]

Dont think people are reading this correctly....sounds like a bad motor until it speeds up again..bit confused myself tbh

It's one of those things that would be easy to diagnose if it was right in front of you. A video of the issue occurring would be most beneficial.

 

[hooblah]

It's one of those things that would be easy to diagnose if it was right in front of you. A video of the issue occurring would be most beneficial.

Hopefully coming this weekend.

 

[not done it yet]

Hopefully coming this weekend.

By then, I would hope you would have found/isolated the problem area.

 

[hooblah]

Ok first use of the lathe in months. Turns out the motor pulley slips when the chuck stalls. How do I go about tensioning the belt? Does someone make a ribbed pulley kit to replace the vee belt setup?

 

[tigdlo]

I don't think the single v velt setup from the motor to the countershaft should be upgraded, if it's in good condition and correctly tensioned then it will provide all the torque that is appropriate for the lathe. If you replace it for something that can transmit more torque then what will be the next weakest point?

Take some photos, it probably just needs a clean up and maybe a new belt. The motor plate angle adjusts the belt tension, there should be a strap with a slotted.

 

[brightspark]

if you look on post 15 theres a lever that operates a cam on the counter shaft that slackens the belts . to the left of it theres an adjusting screw with a locknut . if the main belts slipping screwing it in tensions the main drive belt . once adjusted check the motor belt to counter shaft. if its slack undo the motor plate 4 nuts and bolts and slide the motor till the belt is tensioned and tighten up job done. the motor belt is easy to change but the main one needs the head stock spindle to be removed and refit or you can buy a link belt and fit it without removal

 

[GRW]

If a pulley slips then you'd be thinking tension (on anything motor/belt driven).
If the motor stalls (under a load it should or used to do no problem.... then you have to look at the motor.
(If both, then could be an overload or a combination of load and a sub-par drive motor)
Worn/Sticking Brushes will make a motor gutless, or if the run capacitor is on its way out (check it's actual microfarad reading against its rating on the casing, & if it ain't close to the stated rating, tis fubar). Worth checking before writing a motor off as kaput.