Having awful chatter when parting with 8L lathe

Lathe
1

Howdy,

I would like to preface this by saying I am a complete beginner when it comes to machining. However I’ve recently gotten my hands on a 8L, which for the most part has been great. But I have had some really awful problems with chatter, especially when parting. I’ve tried as many solutions as I could research (listed below), and I just cannot seem to solve my issue, so I thought I would turn to the forums for help. All of my attempts have been done using a Tormach 37128 parting tool. Thank yall for the help!

Steps I’ve done already

  1. Changed the GTN-3 Insert
  2. Ensured the tool post was parallel with the spindle, using a precision dial
  3. Tightened the toolpost down to 20 ft-lb (endured it was still parallel)
  4. Added tail stock support
  5. Ensured tool was tight and straight in the quick change tool holder
  6. Tightened the gibs for both X and Z
  7. Ensured everything was tight before starting my program
2

When I first started machining I discovered that it’s a lot like gardening. If you’re having a problem it because there’s too much of something, or not enough of it. Turning, especially parting, seems to amplify this.

Since you’ve already tried the various mechanical things, my suggestion would be more speed, or less along with more feed, or less. I know that’s not really helpful but that’s honestly the best advise I can give you.

Plan on breaking some tools and wasting some material but just (SLOWLY) adjust the spindle speed and feed rate up and down to see where the chatter gets worse or improves. Change one at a time though and when you find something that works, make a note of those parameters for next time.

3

Thanks I’ll give it a shot today, I also want to see if a different insert type may help, specifically one that is a neutral cutter. I would like to say I’m still having this problem with a very slow manual jog, even using step instead of continuous at the smallest setting I’m still hearing and seeing instant chatter.

4

slow the rpm down or more feedrate

5

@Porter_Light can you tell us more about what you are trying to do?

  • What material are you trying to cut?
  • What is your SFM, in/rev, MaxRPM and so on?

I run the following on 303SS while using our parting tool:

  • 100 SMF
  • 0.002 in/rev
  • MaxRPM: 1000

On my 8L at home I upgrade to a thiner parting tool as well. I use this one from Shars: 1/2" External Cutoff Grooving Turning Tool Holder Right Hand 2 mm MGMN

The thinner insert makes parting easier.

6

I part everything about 600 to 800 rpm. 0.0015 in/rev. Accurately set tool, really don’t need to flip and face. Aggressive parting just causes problems.

7
8

Seems like more stuff to go wrong. For me simple is more reliable. If the end mill breaks, should be nice and smooth. Need to be able to know it’s supposed to be cutting and look for no vibes.