lathe rules of the trade

[Rocketmachinist]

I worked with a guy for a while that was exclusively a lathe machinist but didn't like sharing what he knew. Now that he is gone I am stuck with doing everything around the shop including cnc lathe. I have some questions hopefully someone can help.

• Is there any rules to how far I can stick out my part. He had mentioned something about when i cut aluminum pie jaws there is a ratio of how far I can hold my part out like (1 inch bore into my jaws and I can hold my part out 6 inches or something like that.)
  
• Is there a rule to the clamping pressure of the chuck. I understand It would be relative to the material, the size of the part, is it hollow, and spindle speed, but where is a good starting point
  

Any other help would be amazing

[mkd]

6:1 ratio sounds good to me, but really depends on how much you need to cut all at once, and how far from the chuck that cut is taking place.

generally if the part gets winged outta the chuck, you may want to rethink the method. J/K

 

also the length vs diameter ratio will determine what you can get away with and not have a center-support.

 

answer is vague, cause in typical engineer speak; it depends.

[mkd]

post up a specific job spec.

people more knowledgeable than me will chime in with exactly how they will attack it.

[GoetzInd]

 

As far as you can with out launching it. For example, this is too far......

[Newbeeee™]

Don't forget 'sharp end to the metal'

 

Ref chuck pressure - difficult this one because it's machine specific depending upon the actuator size.

For jobs such as rings which are thin wall, we'll put a manual chuck in bored jaws on the cnc so we can pysically grip knowing how much force we've applied.

You always want to hold 1.5d of material if you can as well (or at least the length of the jaws for engagement).

[Del.]

Do it like I was trained. Give it all she's got till part comes out and then back off 1 notch!!

[crazy^millman]

I have done 316 SS sleeves holding to 1/2 of Material sticking out 22" really comes down to how crazy you are.

[Chipmakr]

I have done 316 SS sleeves holding to 1/2 of Material sticking out 22" really comes down to how crazy you are.

 

With a steady rest or a tailstock on play?? If not please share how.