Need Help! Threading G76 on Fanuc 5T - CNCzone.com-The Largest Machinist Community on the net!

RGeo · #1 06-20-2010, 09:21 PM

Old Mazak Slant 50 with a Fanuc 5T control
OD threads cut well, but when it cuts ID threads, the pitch is wrong, i.e. trying for 20TPI, getting 24TPI
Using G76 for both ID and OD.
As far as I recall the code is similar to:
G01 X0.0 Z1.0 F0.02
G76 X0.5 Z2.0 K0.025 D0.0006 F0.05

sinha_nsit · #2 06-24-2010, 11:29 PM

It is difficult to believe that the pitch is correct on OD thread but not on ID thread.
If the problem is at the start of the thread, increase Z-clearance at the start point of G76.
And, do not manipulate RPM override during threading.
Must use G97 (constant RPM).

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