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Od threading copper without damaging the thread

Tinhsoftware

Plastic
Joined
Feb 5, 2022
Hello, I need some advice. I have a project that i need to cut an od thread 18x2.5 iso 1.500 inch long on a cnc lathe (fanuc contoll). I use 16er 2.5iso, but the threads come out damaged badly. I can have nice finish on other material (aluminum, sst...) but copper. I always use G92. Thank for your help and advice.
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi Tinhsoftware:
You will never get there single point threading C101 or C110 copper because the chip is trapped in between the flanks of the thread as it's being created, so it trashes the developing thread, especially at the crest.

You have two choices:
1) Change the grade of copper to C145 tellurium copper (it's free machining and will break into small chips)
2) Change your process from single point turning to thread milling, thread whirling or thread rolling.

Thread rolling is best (if you don't need to care about how the thread crest looks) because there is no chip at all but the crest is folded over on itself.

Thread milling and thread whirling are better than single pointing because the chips are discontinuous and can fall free more easily without scarring the thread flanks.
Also, you can support the skinny thread crest with the material you haven't cut yet which you cannot do when single pointing.

Last you can try different lubricants...some have advocated buttermilk for machining copper.
Just be prepared to accept the smell when it goes rancid!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
 

Illinoyance

Stainless
Joined
Aug 24, 2015
Does your controller let you choose between plunge feed,flank feed, or alternate flank feed? As Marcus said the chip being trapped between the flanks of the thread causes tearing. Try flank feed or alternate flank feed to see if that will eliminate tearing.
 

Tinhsoftware

Plastic
Joined
Feb 5, 2022
Lets try to see

Does your controller let you choose between plunge feed,flank feed, or alternate flank feed? As Marcus said the chip being trapped between the flanks of the thread causes tearing. Try flank feed or alternate flank feed to see if that will eliminate tearing.

My controll can take G76, but i have never tried it. So on the 1st line of g76 should i use Pxxxx55 or Pxxxx60? Thank you
 

dave morgan

Plastic
Joined
Mar 24, 2018
Tinhsoftware,


I have had success threading C110 using G76 along with Full Profile grade CP500 inserts.

Pics are 10-32 and 3/8-16

I found the best results using a 55° flank infeed for the 10-32 (P021055) and 60° for the 3/8-16 (P021060).

Are you using the correct shim?

026.jpg029.jpg



Dave
 








 
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