Thread and countersink gdt callout

[[Pe...]]

Assuming latest asme 14.5

What do you do with it and how do you do it on the CMM?

My thoughts are that the Ø.000L position would apply to the thread and the countersink too; 14.5 doesnt mention much about countersinks but it does say that coaxial features "such as counterbores" (which a countersink is also a coaxial feature) would share the same positional tolerance since it is listed under.  But putting LMC on a Max feature?

Secondly, the position of the thread itself.  Customer has a spec that defines position of a thread to be the pitch diameter, which isn't something we can measure size of.  To get any result off the pitch diameter I need thread locators.  But then still no tolerance off LMC.

So I would first have to try to measure the minor dia, using a max inscribed cylinder with some vertical scan paths to try to get a size to calculate for MMB on -F-, then try to measure the countersink diameter if possible (which might not even exist due to the magic of MAX limits), then install locators and measure and ignore all the LMC since I cant apply it and only rely on MMB from -F-?

[[Ri...]]

Since they are giving you the direction to measure the minor diameter of the thread - here is how I typically measure those types of features. 

4 or 5 linear scans; slow with very tight point spacing; 1/3 stdDev outlier looped 3 times. This will remove the majority of the points where the stylus falls into the "pitch" of the thread. 

Give it a shot, and I hope it nets what you are looking for. 

[[Wo...]]

As far as as position on a countersink. You will presumably machine both the thread and csink at the same time, theoretically they should be close within a few tenths. Since they give you 0.235" max and a regular NASM csink for .138-32 helicoil is 0.180" - 0.210", you can give yourself a massive tolerance by machining the diameter within that range. Unless I got totally confused by LMC and how it works here.

[[Ri...]]

I see the minor diameter being controlled for location in the TP of .010, the actual thread is TP .000L typically by Pitch Diamter and the Pitch Diameter would allow for a tolerance for the modifier L. Also, you have a virtual shift condition for -F- based on the minor diameter tolerance.

Chamfers are a product of the minor diameter drilled hole and are typically controlled from the title block with something like:

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[[Ed...]]

The way I read the FCF is that the minor diameter is datum -F-, and has a position tol. of .010 @MMC and perpendicularity tol. of .002 @MMC.

The countersink has a position tol. of 0 @LMC to datum -F-.

I read it more like figure 10-27