Thread milling

Tim in D · Oct 19, 2011

I've been asked to modify some threads in a microscope turret to take a larger size objective lens. This will be my first thread milling exercise on the Haas Minimill. I'm wondering if you can do multiple passes with a single point thread mill. If I G00 to the hole location, Z down, spindle orient and run the threading code will I be able to take another pass if the thread is not quite correct? I plan to set up some test plates with the proper size holes and get everything "dialed in" before I have a go at the real deal. The material is brass. The thread is something like 25mmx .75.

Thanks

Tim in D

706jim · Oct 19, 2011

Yes, it is possible to thread mill with a single point lathe style tool mounted on a short boring bar. A simple subroutine can be used to generate the helix and repeated a number of times to produce the thread. My suggestion would be to practice on a piece of scrap material and use this to trial fit the new piece. (Ever try to accurately measure an internal thread?)

Ex:
G90 G0 X0Y0 Z1.0M3 S1000(POSITIONS OVER HOLE)
G1 Z-1.0F10.
G41X1.0D01(TOOL RADIUS OFFSET)
M98P2L6(CALL SUB 6 REPEATS)
G40G1X0Y0(CANCELS OFFSET)
G0Z1.0
M30

(SUB)
G91G3I-1.0Z0.05
M99

Tim in D · Oct 19, 2011

Hey, thanks Jim. Now that I think about it, there is no need to orient the tool as it is spinning at the set RPM. The tool will enter the cut at the same position regardless.
Thanks for the code too.

Tim in D

706jim · Oct 19, 2011

You're welcome!

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Tim in D

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