Thread mill (Profile distortion)

[Lassetti]

Hi,
I faced the challenge which I couldn't solve. I need to calculate the relationship between a profile distortion and a diameter of thread mill and represent drafts. I know there are some software programs but I couldn't find them. Does anybody know one?

[Fred the thread]

Hi,
manufacturers of thread mills do no publish this sort of software or reveal the calculations that they use for these tools.
However, the calculation I use for the thread distortion (thinning) is as follows:
Max thread thinning per flank = (s * s * r) / (8* pi * pi * c * (R - r) * R)
where R = Minimum hole radius
c = tangent of thread flank angle (profile angle / 2 when symmetrical form)
S = lead of thread (pitch * number of starts)
r radius of cutter minus thread profile height

and the maximum cutter diameter to avoid thread thinning:
2 * ((r / 2) + square root ((((r * r) / 4) + ( S * S * r)) /(8 * pi * pi * c * 0,02)))

The above assumes that the form on the cutter has not been compensated

This can be drawn out if you have a solid modelling 3D CAD system
If you would like these calculations in a spreadsheet let me know and I will send it on
hope this helps

[Lassetti]

Thanks for your suggestion. But I don't need these spreadsheets. I'm just trying to figure out how the thread flank is obtained by the thread mill. I just understand that the flank which obtained by the thread mill is not equal the flank which obtained by the tap. And the flank depends heavily on a diameter of the thread mill. Am I right?