Thread milling on CNC knee mill

[Kerry Harrison]

Greetings,

I am trying to learn how to mill threads on my CNC converted BP clone knee mill using a 6 tooth carbide thread mill.

To create the G-code I am using the thread milling wizard in Mach3 Mill but notice there is no option for making multiple passes with an increasing cutting depth for each pass.

Being a newbie at thread milling I have to ask if it is normal to mill threads in a single pass? Even if one pass is the way it's done it seems like it would be hard to get nice smooth threads without at least one clean up pass.

I have a thread mill with the proper pitch for the 1-8 UNC threads I want to mill on a steel rod but hate to just run a program without knowing the proper way things should be done. Don't really want to ruin a $100 thread mill.

Info on this subject seems nigh onto impossible to come by so any thread milling tips would be appreciated.

Thanks much,
Kerry Harrison

[MSFAB]

I am no expert but i have been experimenting with thread milling this past couple of weeks. If you go to the vargus website and look at the thread milling catalog at the end it will give all the mathematical formulas needed to calculate this info. I use cutter comp and a subprogram. I am running it on a BP series 1 interact With Hiedenhain Controller. I am using a vardex cutter. My Machine doesn't allow me to circle on with a z movement so i have to use the tangential approach. but it seems Ok i have been doing 3 passes the third being a spring pass, in 1018 steel. I write the code manually. You should be able to circle on cut and circle off. The Vardex catalog will give you picture representation of different approaches to give a better idea. I hope this helps

Cheers
Marcus