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Thread milling with boring bar

MikeJB

Aluminum
Joined
Mar 5, 2007
Location
Aylesbury, U.K.
We were talking with a very experienced CNC machinist and he suggested using a lathe boring bar with a thread cutting insert to mill threads with our Haas VF0. Much cheaper than purpose made thread milling tools.

Will this work OK? Anybody else doing this? Our visitor was absolutely confident that it would work.

Regards,

Mike.
 
Can be done
But its slow, but if you've got no other way of getting a thread in there... or its a one off part with a very odd thread.

Heres an example program for a 20mm*2 thread 40 mm deep
Have not put in any roughing cuts or anything

O1001
T1 S1500 M6
G54 G0 X0 Y0
G43 Z0 H1 M3 // tool height
G1 G41 Y20 H21 F250 // move to tool out to thread dia with comp
M98 P201002 // call the threading 20 times
G1 G40 Y0 // cancel comp
G0 Z25 M5
M30

O1002
G2 J-20. Z-2. // spin the tool around once and down the thread pitch
M99

Boris
 
THread milling with BB

It works, but it's slow.

I did 4" of 2.75-12 thread in mild steel using a HSS tool and boring bar. Feed was 0.3ipm (BB centerline). Set up a subroutine (as above) and went for coffee. Perfect thread, but the tool has to survive for the whole process if its not an indexable insert.
 
If you guys are familiar with the triangle shaped thread inserts (for lathe IIRC), they have three cutting edges, you can mill a triangle pocket on the end of a piece of 3/4 rod, tap a hole and go. Very cheap, and you have three edges instead of one.
 
Thanks guys for your advice; I guess that this technique is best for those one off or last minute jobs when buying the proper tool is not an option.

Regards,

Mike.
 
You can also make multiple start threads if you use your scaling and rotation..... :)KJC

Eh?
Not meaning to pour cold water on your idea but for a M40*2 2 start thread like the single start listed above:

O1001
T1 S1500 M6
G54 G0 X0 Y0
G43 Z0 H1 M3 // tool height
G1 G41 Y20 H21 F250 // move to tool out to thread dia with comp
M98 P101002 // call the threading 10 times
G1 G40 Y0 // cancel comp
G0 Z+2
G1 G41 Y20 H21 F250
M98 P101002
G1 G40 Y0
G0 Z25 M5
M30

O1002
G2 J-20. Z-4. // spin the tool around once and down the thread pitch*number of starts
M99

Boris

And hope the tool does'nt break :bawling:
 








 
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