Acme thread - chatter in base of cut

[dansawyer]

The project is to cut 10 pitch Acme threads in a section of W1 tool steel. I am about half way through a test cut and I am seeing chatter in the base of the cut. The tool is an Acme thread carbide insert. I have the compound feed set to 14 1/2 degrees and feeding with the compound. The cuts are shallow, about 5 thou. Even with this small cut there is significant pull on the cut. After 3 or 4 passes the part is very warm to touch. I am cutting dry. (I really don't have a coolant option at the present. Can I take smaller cuts as an alternative? )
The lathe is a Clausing 13 Engine lathe. The rpm is about 500. The diameter of the part is about .85 inch. The cutter is new. It has a built in rake angle and I have the tool holder level and set about 1/8 inch below center.

 

[DavidR8]

You aren't using any cutting oil?

 

[dansawyer]

You aren't using any cutting oil?

No. I am a relative newbe and have mainly cut slow and dry. Would brushing on cutting oil help this?

 

[DavidR8]

It's definitely a good idea. Any thicker bodied oil will help. Just don't use WD-40

 

[dansawyer]

You aren't using any cutting oil?

No. I am a relative newbe and have mainly cut slow and dry. Would brushing on cutting oil help this?

It's definitely a good idea. Any thicker bodied oil will help. Just don't use WD-40

I just purchased cutting oil. I will pick it up and give it a try. Thanks. Dan

 

[benmychree]

Also, that RPM is way too fast for thread cutting, personally, I would be using a HSS tool at perhaps 150 0r 200 RPM. A carbide tool would be fine on a capable CNC machine, not so much on a relatively light machine such as yours. Better than ordinary cutting oil is TapMagic, I use it for nearly all my work involving steels.

 

[bill stupak]

I've never cut acme threads , but I think the tool should on center and not below 1/8"

 

[benmychree]

I've never cut acme threads , but I think the tool should on center and not below 1/8"

Absolutely, the tool should be on center, its a wonder it cuts at all, I missed that fact in my first reading of it.

 

[DavidR8]

Missed that too.

 

[dansawyer]

Also, that RPM is way too fast for thread cutting, personally, I would be using a HSS tool at perhaps 150 0r 200 RPM. A carbide tool would be fine on a capable CNC machine, not so much on a relatively light machine such as yours. Better than ordinary cutting oil is TapMagic, I use it for nearly all my work involving steels.

Thank you. I will lower the speed to 200 RPM.
I did try some standard oil and that seemed to help.