Here's one I have for a 1" 20 pitch thread.
All you have to do is change the Z movements to match the 11-1/2 pitch. I start the thread at the bottom and cut up one pitch.Code:(THREAD MILL 1"-20) N3 G00 G17 G20 G40 G49 G80 G90 G98 G53 Z0 T8 M06 S5000 M03 G110 X0.9975 Y0. G43 H08 Z1. M08 Z-0.596 G01 G41 Y0.5 D08 F10. G03 X0.4975 Y0. R0.5 (RADIUS APPROACH) G03 I-0.4975 J0 Z-0.546 G03 X0.9975 Y-0.5 R0.5 (RADIUS EXIT) G01 G40 X0.9975 Y0. G00 G80 Z1. M09 G49 G53 Z0 G110 X0 Y9. T9 M06