# Thread: Thread mill (Profile distortion)

1. ## Thread mill (Profile distortion)

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?

2. 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

3. 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?

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