TP of threads

[[Mi...]]

I got a TP callout on a M6x1 threaded insert. They also gave me MMC. Question is what’s the tolerance on the threads so that calypso can add the MMC?? I know the Min and Maj for the threads but how do I apply that? Again I don’t measure threads a lot here so Im kinda in the dark

[[SH...]]

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You can use the app Mech tab.
I hope it is internal thread.

IMG_20200826_222006.jpg

[[Ja...]]

If all they're wanting to see is location and diameter, I usually measure the threaded hole as a cylinder, scanning 4 linear paths slowly and with high point density (remember to use filters and outlier removal). Then I intersect that cylinder with the surface/plane it's perpendicular to (tick 'shell' in the intersection window) and the resulting geometry will be a circle (with an averaged diameter of the cylinder). Use this intersection as your feature for reporting true position, diameter, MMC or whatever you need. As far as applying your tolerance, you do that under the Ø characteristic window.

Also, I sometimes use "circle on cylinder" to extract a circle, use just 4 touch points and then use its actuals to guide my 4-linear scan cylinder; helpful if your machining isn't spot on.

[[SH...]]

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He is asking about thread tolerance...

[[Mi...]]

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Yes another colleague of mine suggested the linear cyl set up as well. I will try this.

But I am also wanting to know how to tolerance the M6 threads so I can get calypso to give me the MMC. I know where to put the info, I just need the numbers. Its a weird callout that I have not seen much. I don't expect to get much if any mmc off the M6 threads. Ridiculous call out

[[Jo...]]

There was some discussion about modifier on thread before.. I think position, functionally, would be pitch diameter. How can you measure pitch diameter with CMM ? I have several prints like that and omit the modifier. That "bonus" tolerance isn't going to help much.

[[Me...]]

MMC on threads is on the pitch diameter. It's almost impossible to do with a CMM unless you have very large threads that you can access with a probe to accurately measure it.

Some prints will specify minor diameter and people will use the tolerance of the minor diameter to calculate MMC, which is usually negligible. This is totally wrong, in my opinion, as threads are self centering, but that's another conversation.

[[Mi...]]

John/Robert I agree. I'm allowed .3 TP. I'm getting .431 so without inputting a diam for the M6 threads, I don't see the Circle M doing me ANY good.

Trying to get them to drop the MMC and do a straight TP with higher tol. NO way I can get into the threaded insert to make a measurement on the pitch.... Yes its an insert and not a cut thread. Its inside a molded plastic block

[[Ja...]]

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You're right. I misunderstood the question.

[[Ma...]]

I believe, that MMC can not be applied to threads - it can not be measured directly.
M6x1 is not full description of threads - missing grade ( 6H, 7H is usual ).

If thread tolerances should be used, then it must be doubled because of insert.
If is insert in no free state ( is not moving ) than it could be MMC for insert ( it's cylinder )

[[Jo...]]

MMC absolutely CAN be applied to threads but as mentioned above, several times, it doesn't buy you much and a CMM isn't equipped to measure the pitch diameter. One big reason for using an MMC modifier on threads is to accommodate the use of a hard gage in the case of a hole pattern. If a pattern of threaded holes is positioned at MMC then expanding thread gages must be used on all the holes.