[j206]

Good day to you all, as a rule I use the Vargus Threading software for code generation when milling thread forms but we have threadmill cycles on FC so I decided to have a look at them the other day to produce a 0.5-13 UNC thread form. Looking at the NC code generated I was confused to see that the diameter generated would have been 0.519 as opposed to 0.5 (0.426 dia cutter drives out to X0.0463 from X0.0 Y0.0 and interpolating with a 0.0463 radius )

I understand we are working with a 0 dia offset for the tool and we would have backed it off anyway by 0.005 and worked it in but can someone explain why the system would create an oversize hole in the first place?

Many thanks.

[Perfect Circle]

The default that FC puts into the thread height is wrong.
The minor for a 0.500-13 is 0.4225 nominal. and the thread height is 0.03725
If you plug these into FC thread mill you should come out correct if you use the exact diameter thread mill.

Good Luck~! :cheers:

G0 G17 G20 G40 G80 G94
T1
M6
G54 G90 X0. Y0. S2577 M3
M10
G43 H1 Z1.0 M08
Z0.1
G1 Z-0.5815 F8.825
G41 D01 X0.0313 Y-0.0082 F2.2062
G3 X0.033 Y0. Z-0.5769 R0.0213
X0. Y0.033 Z-0.5577 R0.033
X-0.033 Y0. Z-0.5385 R0.033
X0. Y-0.033 Z-0.5192 R0.033
X0.033 Y0. Z-0.5 R0.033
X0.0313 Y0.0082 Z-0.4954 R0.0213
G1 G40 X0. Y0. Z-0.5
Z-0.5815 F8.825
G41 D01 X0.0313 Y-0.0082 F2.2062
G3 X0.033 Y0. Z-0.5769 R0.0213
X0. Y0.033 Z-0.5577 R0.033
X-0.033 Y0. Z-0.5385 R0.033
X0. Y-0.033 Z-0.5192 R0.033
X0.033 Y0. Z-0.5 R0.033
X0.0313 Y0.0082 Z-0.4954 R0.0213
G1 G40 X0. Y0. Z-0.5
G0 Z1.0
G28 G91 Z0. M09
G28 G91 Y0. M5
M30