GD&T question for 2 keyways on shaft

[potrero]

Please see attached drawing for details - comments are enabled in the PDF...

I've got a shaft with 2 keyways, which should be inline with each other along the shaft. My question relates to how to properly spec the drawing; is it sufficient to use "2X" and only detail one keyway, or is there a better way to detail this drawing? What is the appropriate way to indicate that I want the centerplanes of each keyway to be coplanar with each other (with a bit of tolerance)?

Thank you.

 

[powerhound]

Xplicator,
I thought that by your statement - "And if you use position invoking BOUNDARY on the pattern of key slots, a tertiary is not necessary unless you need control of other features to the key slot." - that you were saying that BOUNDARY was required to invoke simultaneous requirements. Sorry for the misunderstanding.

Powerhound, GDTP T-0419
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[drawoh]

Xplicator,

You originally said that the datum should be the mid-plane between the two shoulders. It sounds like your original assumption was correct, however, your terminology was bad. Applying datums to centre lines is a common error on drawings that (are supposed to) conform to ASME Y14.5M-1994. I suggested the option of using the dimension across the shoulders as the datum, which I believe is what you actually meant. Since the two shoulders are a feature of size, you have to at least consider calling the datum up at MMC, although it is an accurate tolerance, and I think all you are doing is locating slots lengthwise. You would get away with it in this case.

When you call up a feature of size as a datum, you need to think about the fixturing.

Your are right about datum_D. This is defined by datum_A-B. Datum_D is not needed unless location to the first slot is more important than location to the shaft ends.

JHG