Lathe Stall

[Beez12]

Well this has been re occurring daily on my new machine. Regardless of material (4140, brass, mild steel) the spindle is stalling with very small depth of cuts (0.005 at 800 rpm) with freshly sharpened HSS or Carbide tooling. I replaced the primary drive belt with a new one and that never made a difference. The only belt left to change is the variable drive speed belt (which is captured in the head stock). Waiting for KMS tools to open so I can pick up a link style Vbelt.

What else could cause this stalling? I’m not hearing any irregular noise from the motor when it occurs.
Pictures of worn v belt to follow shortly.

 

[Beez12]

Please tell me that this is the problem!

 

[YYCHM]

That doesn't look to healthy LOL So the lathe stalls but the motor is still chugging away?

Lee Valley carries link belt as well. You might want to compare prices.

What length do you need? I have a length that's too short for my use. About 30" worth.

 

[Beez12]

When the spindle stalls the primary drive belt is still rotating to the head stock.

Need about 28” of length, and the belt is 5/8”.

 

[YYCHM]

When the spindle stalls the primary drive belt is still rotating to the head stock.

Need about 28” of length, and the belt is 5/8”.

What I have is 1/2"

 

[Beez12]

Thanks anyways Craig, after the long weekend is over I’ll find something. Hoping it resolves the issue and isn’t the clutch mechanism that’s causing the stall!

 

[Brent H]

@Beez12, that belt is very very loose. Also what kind of motor is driving things? Single phase or DC etc - Does the motor stop when things stall or is it spinning and the belt stops? From the looks of things - check the motor/belt tensioner - something might be very loose

 

[Beez12]

The belt slacks off when the head stock cover is opened. Motor is single phase 120 ac. The motor continues to turn when the lathe stalls

 

[RobinHood]

Hoping it resolves the issue and isn’t the clutch mechanism that’s causing the stall!

I would check the clutch for proper operation anyway. Too many have been burned-up by improper adjustment. And no, less slip is not always better. Try to find the specs of how it should be set and adjust it to that. It will give the longest life and best performance overall.

 

[6.5 Fan]

Ya i would check for proper clutch engagment, also that the pin in the gear is in proper place for back gear or direct drive.

 

[Beez12]

Okay well belt change didn’t have much change on the depth of cut. Clutch mechanism re adjusted and it does appear to be the problem. I finally check the motor specs and it’s a GE 60 Cycle Single Phase 1/2 HP. Could this be the problem, half a HP doesn’t seem like much for a 12x36 machine.

 

[YYCHM]

Okay well belt change didn’t have much change on the depth of cut. Clutch mechanism re adjusted and it does appear to be the problem. I finally check the motor specs and it’s a GE 60 Cycle Single Phase 1/2 HP. Could this be the problem, half a HP doesn’t seem like much for a 12x36 machine.

The clutch does appear to be the problem or doesn't appear to be the problem?

If the motor is bogging down that symptom will be pretty obvious.

 

[Beez12]

Sorry typo, clutch doesn’t appear to be the problem

 

[YYCHM]

When you stall the spindle is the motor stalled as well?

 

[Beez12]

Nope drive belt still continues to turn, so obviously the motor is okay. All I want to do is make a 20 thou depth of cut already!
Craig, if this was your problem what would you do next?

 

[YYCHM]

Nope drive belt still continues to turn, so obviously the motor is okay. All I want to do is make a 20 thou depth of cut already!
Craig, if this was your problem what would you do next?

0.02" is getting up there for a small lathe actually BUT. Is your spindle totally stalled?

Something is slipping.

I've never stalled my machine (1/2 HP motor, 1/2" V-Belt) while turning something. It either breaks the tool or spins the tool post. I have stalled my machine while drilling and having a ooops moment and locking a chuck jaw up on the saddle. In those instances it stalls all the way back to the motor and either trips the power bar breaker or I catch it in time with the ESD switch.

 

[Beez12]

Yup spindle completely stalls while running in direct drive. Back gear works good tho, snapped a parting blade yesterday. No slippage there LOL

 

[YYCHM]

I don't have a clutch and don't know what a back gear is or what direct drive means, some one with a similar machine needs to comment.

Your lathe has a countershaft assembly doesn't it? Mine doesn't.

 

[RobinHood]

Are your dials reading radius or diameter? 20 thou depth of cut is 40 off the diameter.

1/2 hp is not a whole lot of power for a 12” lathe. What spindle rpm do you think you are getting in the direct gear you are in? How are you determining which parts of the drive train still turn when you “stall out” the spindle? Will the lathe run with the cover open? - it looks like the cover slackens the belt.

You need to somehow find a way to verify each component of the drive train is / is not turning when the spindle stops. I wonder if there is a sheared / missing key somewhere. Enough friction to turn the components with no load, but no longer when taking a cut?

How about this:
-unplug the lathe
-block the motor so it can not turn (make some sort of clamp out of wood for the pulley)
-chuck a piece of scrap in the late
-select the same gear(s) that you have issues with
-engage the clutch
-use a pipe wrench to turn the part
-look carefully along the drive train components to see what slips (you may have to put witness marks to see that)

 

[Dabbler]

My 12" has a 1 1/2 HP motor. But my belts don't slip, either... So I think your belt is slipping in the pulley?