TP callout for two bearing counter bores

[uptick]

Hi there,
I need your opinion on the case below:
Problem: A buterfly valve with a shaft goes thru both side of the wall. Each side has a bearing bore callout.
1. The hole for the shaft is a thru hole with diameter A +/- tol with a datum A callout.
2. The bearing bore on the right states 2 X diameter +/- tol (for two bearings bores) with a TP of .002" to datum A.
3. They call out a datum C on the bearing bore on the left of the body with a TP of .003" to datum B-C.
Question:
a. Is the callout in item 3 above valid? and good control?
b. Does the 2X diameter +/- tol with a TP of .002" to datum A in item 2 above apply to both bearing bores, regardless the callout in item 3 above? In other word, the callout in item 3 above is NOT REQUIRED.
Your earliest help is appeciated.
Uptick.

 

[uptick]

Sorry. The datum B callout is missing in the bearing bore on the right (item 2.
Hope to hear from you soon. Thanks
Uptick

 

[desertfox]

Hi uptick

Please post a sketch its far easier to see and follow rather than your description.

desertfox

 

[ewh]

Please do not cross-post, as it is against site policies.
The GD&T forum is the correct location for this question.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[MikeHalloran]

Primary datum should be the butterfly bore.
The shaft bores are tertiary at best.



Mike Halloran
Pembroke Pines, FL, USA

 

[uptick]

Hi all,
Sorry. I posted in the wrong place before I posted this here.

Mike: The datum A (the shaft thru hole) is already tight to the butterfly bore which I did not present here. Now the issue is the bearing bores are controlled the A. I wont to know if the callout is correct (valid). I know the total runout for C to B is the best, but does this one (TP callout) work?
Thanks,
Where is KENAT?
Uptick.

 

[MikeHalloran]

Functionally, the shaft bore doesn't come into play until the bearings are worn out. Why include it in the stackup?



Mike Halloran
Pembroke Pines, FL, USA

 

[uptick]

Sorry ewh. I did post overthere after finding out the correct location.

 

[uptick]

Here is the sketch

 

[KENAT]

Where is KENAT?

Working the job that pays my bills. I'm not overly familiar with valves and didn't follow your description well enough to comment.

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[desertfox]

Hi uptick

I think you can't reference B&C to themselves which is what you appear to have done.
What I would do is have B&C as your datum and then use runout of the bore datum A (thru hole) to the datum B&C.

desertfox

 

[desertfox]

Hi uptick

Further to my last post your tolerance figures should actually be derived from the clearance between bearing internal diameters and shaft diameters, ie when the bearing housing holes are misaligned and the bearings and shaft have minimum float, you should still be able to assemble all the components.

desertfox