GD&T of a counterbored slot

[CroninD]

Hi guys,

Relatively new to GD&T. I have a base plate in an assembly with two counterbored slots in it. I know how to geometrically tolerance a normal UN-counterbored slot; i.e;
Link

How do I go about it if the slot is counterbored from the underside to give clearance for a socket head cap screw? Is it the same as dimensioning a counterbored hole minus the diameter symbol? Or should i tolerance the top and counterbored sides seperately?

Any help is much appreciated.

D.

 

[KENAT]

I'd probably tolerance/dimension as two 'coincident' slots where one of them has a depth associated. I'd probably dimension the depth in a section view just to make clear.

If using position & envelope principle to locate the slots I think this should work OK and minimize chance of confusion.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[CheckerRon]

I've done this before and there is a couple ways. You can dimension the slot and the counterbore slot to the same datums each having it's own FCF and maybe a relaxed tolerance on the counterbore, or you can positional tolerance the slot a per the standard and give it a datum, say D. then tolerance the counterbore slots to datum D, "4X INDIVIDUALLY" (or however many there are).