Myford ML7 stalling under load

[hooblah]

I was drilling a 12mm hole earlier in a bit of en16. It got 3/4 of the way through and then started stalling repeatedly. Everything was spinning without slipping, just the chuck wasn't. I was running on the fastest speed so I moved it down to the slowest speed. Turns out it stalled even easier!

Is there some sort of clutch in the spindle, and can it be adjusted?

 

[brightspark]

I was drilling a 12mm hole earlier in a bit of en16. It got 3/4 of the way through and then started stalling repeatedly. Everything was spinning without slipping, just the chuck wasn't. I was running on the fastest speed so I moved it down to the slowest speed. Turns out it stalled even easier!

Is there some sort of clutch in the spindle, and can it be adjusted?

no clutch on the spindle .fastest speed drilling a 12mm hole needs to be the slowest without going in to back gear

 

[hooblah]

It stalls even easier on the slowest speed. I drilled through with a 5mm and followed it with the 12mm, intermittently squirting oil at it.

 

[Richiew]

What state is the drill bit? Try a new one maybe? It is night and day between a blunt and a sharp drill on a little lathe.

 

[hooblah]

It was a new chinesium bit when I started. It then started to get stuck at so I reground it many times, to no avail. Eventually used a new dormer bit which went through like butter.

Still, I'd like to know why this lathe keeps stalling like that. And what I can do to stop it.

 

[Richiew]

Belt slip?

 

[hooblah]

Belt slip?

Read again.

 

[gaz1]

if your chuck wasnt spinning theres a piece inbetween that wasnt spinning

so that means you wasnt direct to the spindle bar itself the tapper bit with a threaded end that you can screw your chuck direct to the myford

so means you have an add on inbetween the chuck and spindle

 

[hooblah]

Ok. So is that normal? Is the add on from factory or aftermarket? I can't see anything suspect.

 

[gaz1]

if you have a back plate its an add on

Suit Myford Backplate 100mm Cast Iron 4" Chuck Back Plate 1.1/8" x 12 TPI | eBay

Myford lathes have 3 different common bore sizes, 1", 1-1/8" and M42.5. Also, as per the various chuck PCDs, it is also necessary to drill and possibly tap the backplate to accept whatever chuck is being mounted.

www.ebay.co.uk

as this will also fit your chucks

myford also have a direct to spindle chuck

GENUINE BURNERD 34M - 6" 4 JAW INDEPENDENT CHUCK for ML7 and Super 7 lathes | eBay

GENUINE BURNERD 34M. This will fit ML7 & Super 7 lathes. 6" 4 JAW INDEPENDENT CHUCK. and has a recessed 1 1/8" x 12tpi thread for less chuck overhang. the item you see in the photo is the actual item you will receive.

www.ebay.co.uk

so unless you have lost your threads on the spindle or chuck

GENUINE MYFORD LATHE -Myford ML7 headstock spindle | eBay

GENUINE QUALITY USED MYFORD PARTS.

www.ebay.co.uk

then its either your bolts or the spindle

 

[Agroshield]

Read again.

Write again, more clearly obeserving and then describing the problem. If we take your original words literally ("everything was spinning... ...just the chuck wasn't"), gaz1's solution is the only possibility.

Start at the motor. It has a pulley on it. Is the connection between pulley and motor shaft tight? Is the belt that is driven by this pulley slipping? The pulley that is driven by this belt is on a countershaft. Is the driven pulley secure on the countershaft?

At this point, we cannot go much further because there is not enough information: ML7's came with no clutch, a clutch and a tri-lever arrangement. So you now have to describe your machine or post a photo of it.

Let us assume the simplest set up of no clutch. The countershaft will have a three step pulley on it in addition to the one driven from the motor. Is that pulley tight on the countershaft? The three step pulley on the countershaft drives another three step pulley on the spindle itself via a belt. Is that belt slipping?

The three step pulley on the spindle is locked to the spindle in direct drive and loose on the spindle in back gear. Have you confirmed the back gear locking pawl is properly engaged and in good condition? I would not impose this fellow on my worst enemy, but his video might help if you are not familiar with how the back gear works:

 

[Alan Reynolds]

Write again, more clearly obeserving and then describing the problem. If we take your original words literally ("everything was spinning... ...just the chuck wasn't"), gaz1's solution is the only possibility.

Start at the motor. It has a pulley on it. Is the connection between pulley and motor shaft tight? Is the belt that is driven by this pulley slipping? The pulley that is driven by this belt is on a countershaft. Is the driven pulley secure on the countershaft?

At this point, we cannot go much further because there is not enough information: ML7's came with no clutch, a clutch and a tri-lever arrangement. So you now have to describe your machine or post a photo of it.

Let us assume the simplest set up of no clutch. The countershaft will have a three step pulley on it in addition to the one driven from the motor. Is that pulley tight on the countershaft? The three step pulley on the countershaft drives another three step pulley on the spindle itself via a belt. Is that belt slipping?

The three step pulley on the spindle is locked to the spindle in direct drive and loose on the spindle in back gear. Have you confirmed the back gear locking pawl is properly engaged and in good condition? I would not impose this fellow on my worst enemy, but his video might help if you are not familiar with how the back gear works:

I thought it was just me who found the accent very irritating where he extends vowels.

 

[mtt.tr]

Does this have the clutch like the super7

 

[tigdlo]

Everything was spinning without slipping, just the chuck wasn't

So the chuck isn't attached to the back plate?

 

[hooblah]

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.

 

[mtt.tr]

Thanks for all the replies. 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?

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

is the lower pulley grub screw tight?

 

[brightspark]

squeeze the belt tight with your hand and turn the chuck see if it slips .is the little slide cog locked in on the backgear

 

[JMS1972]

Maybe the motor is weak. Is it a 3/4 HP one?

 

[Rannsachair]

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

Myford ML7s had an optional clutch, I had one on mine, top left handle:

My belts used to slip before the motor stalled. Lots of good advice above

 

[MattF]

Check the bull gear is tightened onto the spindle fully.