Correct GT&D for bore on vertical centre line

[Carra]

I need some help on a part I am designing. I have a cylindrical part with two ODs, I need a hole to be located on the smaller OD (tolerance of +/-.002") and centred on the vertical centreline of the part (also tol +/-.002). I know that I cannot use a centreline as the datum and am wondering on the correct way to dimension this part. Thanks for your help

 

[KENAT]

Is there some other un-shown feature identifying the orientation - i.e. how do you physically define what the vertical 'centerline' is?

Whatever this feature is needs to become a datum most likely.

Posting guidelines faq731-376

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

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

 

[drawoh]

Carrs,

You need a feature to define your centreline. You can use your hole to define it. The only tolerance you need is the location on the circle.

--
JHG

 

[Carra]

KENAT/drawoh

Thanks for the quick response.

The feature that defines the vertical centreline are two other holes at 45 degrees as shown in attached sketch, however I am not sure how to use these features to define a datum.

 

[KENAT]

So, depending on function, would it make more sense for the single hole you originally asked about to be the datum and index those 2 threaded holes from it?

Posting guidelines faq731-376

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

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

 

[Carra]

There are some other separate features that I want to tolerance to the centreline so I was hoping to find a way to show the vertical centreline based on the 45 degree holes as a datum.
Also what is the correct way to show that the hole is located on the diameter and include the tolerance?

 

[drawoh]

Carra,

It is legal to call up each of the tapped holes as a datum, but it will be a pain to fixture in the shop. Why not use your bore as a datum, and locate everything else to it, as we are suggesting, above?

--
JHG

 

[Carra]

Drawoh/Kenat: Sorry for delay in replying, I took your advice and used the bore as a datum with the tapped holes located from the datum. Thanks for all your help