Position of Stub Acme Thread

[[Da...]]

Hello, I am new to CMMs in general, so please keep that in mind when responding.

I have a position callout of a threaded hole, and while I understand using a helix path to locate, or using a hole location gage, this thread has a couple oddities.
For one, it is a Stub Acme thread. I do not see any options to purchase a hole location gage for stub acme threads.
Also, the thread has multiple gaps, so I am not sure how to do a helix path without it hitting a gap.
Thanks in advance for any advice.

[[Ri...]]

How big is this thread?

[[Da...]]

1.750 - 12 Stub Acme

[[Du...]]

what exactly do you mean by multiple gaps. ive had to run quite a few stub acme threads on my machine, could you post a picture of it or the print?

[[Da...]]

[[Ph...]]

Depending on the accuracy needed ("Cyl. Form Lines", "line scans", "Linear Paths") seem to work well for location. Name will depend on the software version. I use 16-20 pts per thread inch depth and scan slow about .2" in speed, and 8 lines per cylinder.

[[Du...]]

ahh, i see now. at this point I don't think you would be able to do a helical path but maybe you could do multiple linear paths down the thread and set your evaluation to inner tangential. i used this a few time with success

[[Ma...]]

If you have a rotary table you could construct a cylinder from a number of self centering points or even helical scans between the interruptions. It may also be possible to accomplish this with a miniature start probe without a rotary table.

[[Gr...]]

You might try using a cylindrical stylus and points without scanning. This avoids probing between the threads.

[[Je...]]

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Outer Tangential

Outer-Tangential will represent and interfacing perfect gage.

If measuring as a circle, (Flyscan from VAST Peformance option is made for scenarios like this) measure slow and overlap data. Evaluate as Outer-Tangential to get your minor diameter as measured with a gage pin. Careful with going heavy on filters and outliers as this can easily affect your data.

If measuring as a cylinder, use several circle scans in the same manner with as much feature depth as possible. If your diameter is greater than your bore depth between furthest scans, revert to circle feature as the feature type. Axis projection could become an issue due to feature geometry.