- #1
FranzS
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- TL;DR Summary
- Deviations from the nominal thread profile due to tilting angle of the cutting insert?
Hello CNC experts!
For threads with a high "pitch to diameter ratio", so to speak, the manufacturers of cutting inserts for CNC threading suggest tilting the insert at an angle ##\lambda## with respect to the ##z## axis (spindle axis on a lathe), so that the cutting edge/surface of the insert will work perpendicular to the groove it's "digging" (though that is true only at a very specific diameter [##x## coordinate on a lathe], but let's not get into such tiny details).
See for example what the manufacturer Sandvik Coromant writes (link: https://www.sandvik.coromant.com/en.../how-to-choose-thread-turning-insert-and-shim):
My question #1 is: wouldn't such a tilting "widen" the profile of the resulting thread (i.e. increase the flank angle with respect to its nominal value) when the cross-section of the thread along the ##z## axis (not considering angle ##\lambda##) is inspected?
I guess the "widening" of the flank angle due to the tilting is so small that it is still within the tolerances indicated by the standards?
And here's my question #2, closely related to the previous one: is the nominal cross-section profile of a thread (ISO, etc.) to be considered along the "threaded stem" axis (i.e. the lathe's ##z## axis) or perpendicular to the thread helix (thus taking into account the ##\lambda## angle)?
I've always thought the former was the correct cross-section to be considered.
Thanks for your attention.
For threads with a high "pitch to diameter ratio", so to speak, the manufacturers of cutting inserts for CNC threading suggest tilting the insert at an angle ##\lambda## with respect to the ##z## axis (spindle axis on a lathe), so that the cutting edge/surface of the insert will work perpendicular to the groove it's "digging" (though that is true only at a very specific diameter [##x## coordinate on a lathe], but let's not get into such tiny details).
See for example what the manufacturer Sandvik Coromant writes (link: https://www.sandvik.coromant.com/en.../how-to-choose-thread-turning-insert-and-shim):
My question #1 is: wouldn't such a tilting "widen" the profile of the resulting thread (i.e. increase the flank angle with respect to its nominal value) when the cross-section of the thread along the ##z## axis (not considering angle ##\lambda##) is inspected?
I guess the "widening" of the flank angle due to the tilting is so small that it is still within the tolerances indicated by the standards?
And here's my question #2, closely related to the previous one: is the nominal cross-section profile of a thread (ISO, etc.) to be considered along the "threaded stem" axis (i.e. the lathe's ##z## axis) or perpendicular to the thread helix (thus taking into account the ##\lambda## angle)?
I've always thought the former was the correct cross-section to be considered.
Thanks for your attention.