Need help with NPT threads in Mastercam x9

[tuantrinh]

Hi guys,
Please school me.

I draw this NPT internal threads following the drawing but it's over-sized. is there something that I should do more than the drawing, right?
I found dimensions but I dont know how to put it into Mastercam.

Thank you guys.



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[Zenji]

You have to go the long hand way without cam, im thinking helical interpolation programmed in quadrants. Maybe use mastercam to draw a 3d spline of your tapered thread, break spline at qaudrant with line in 2d views and then use convert to arcs feature to obtain polar information to write program. It should read something like G3X10.Y10.Z-3.R10. And automatically should calculate the polar anchor point. Repeat this for however many quadrants, if one decimal place is wrong then all the code will fail.

[g-codeguy]

No version of MC will do that thread that I know of. At least not in the normal way a thread is done. The 3/8 in. straight section is the killer. You probably could make a thread with zero lead-in and 0 degree infeed. However, I don't know how good the beginning of the thread would be. I've done some threading with a very short starts before the material. RPM has to be held down so the turret can accelerate to the correct feed in a short distance.

Personally I would write it long hand and hope for the best. Too bad many engineers and designers never actually know how to machine a part.

[GcodeEng]

Use a grooving cycle and edit your post to output G92 moves

%
:0001
G21
(ROUGH SCREW CUT ACME THREAD FORM)
(THIS PROGRAMME IS TO RUN IN CONJUNCTION WITH.....)
( ROUGH THREAD )
( TOOL - 1 OFFSET - 1 )
( LGROOVE 3MM BUTTON )
G0 X300.000 Z300.000
G99
G0 T0101
G97 S600 M03 M41
G0 X48.196 Z-9.586 M8
G92 X43.451 Z-146.000 R0 Q0 F6.35
G00 Z-9.586
Z-9.289
G92 X43.451 Z-146.000 R0 Q0
G00 Z-9.289
Z-9.884
G92 X43.451 Z-146.000 R0 Q0
G00 Z-9.884
Z-8.991
G92 X43.451 Z-146.000 R0 Q0
G00 Z-8.991
Z-10.182
G92 X43.451 Z-146.000 R0 Q0
G00 Z-10.182