View Full Version : Chucks and Roughing

06-03-2012, 10:43 PM
hi all. I currently have a 1HP belt drive lathe. Now 2 problems When roughind 2 inch bar (medium hardness) i can only push about 1mm cut before i get chatter. Speed is 250 RPM, feed =.044 inch. Is this good size cut for this lathe? also any deeper cut and the bar slides back up into the chuck..Is this normal?

06-03-2012, 11:03 PM
Your chuck has a problem... or your tooling is dead.

Feed and doc are not just related to hp, but the rigidity of the machine.

Exactly what lathe are we talking about?

06-03-2012, 11:38 PM
How far out of the chuck do you have the work extended? It is supported between centers or the chuck only? What tooling, HSS or Carbide? What condition is your chuck in? Bellmouthed? Does it need to be cleaned and lubricated? Is your tooling properly ground and sharp? What is the radius of the tip of the tool? If you are saying .044" per revolution is high, try .010" to .015" per revolution for roughing.

At this point I am going to suggest you get South Bend's How to Run a Lathe. It's inexpensive and contains a wealth of information for lathe use.

06-04-2012, 01:44 AM
:eek: .044" feed is cutting a thread. Do you mean .0044" feed? 1mm is about .039" so is that the depth of cut or off the diameter?

If your using .044" feed with .039 DOC I can see why it is pushing the material into the chuck. That's way more than a small lathe can handle.

06-04-2012, 07:23 AM
sorry about this just checked again and feed is 0.0046 inch and cut is fed in 1mm therefore reducing diameter 2mm

06-04-2012, 09:27 AM
Ok, now if you lightly touch the jaws on a shaft and wobble it around as you turn the chuck key to lightly tighten the jaws does the shaft ever stop wobbling around. If it wobbles all the way up to the point of the jaws are tight then the jaws are probably worn and not flat. In other words the jaws are bell mouthed. If that is the case, and I think it is, then the jaws need to be ground.