Verification of a GDT Use

[JasonNicholson]

I am self training on GDT. I need to use it so that I maintain that the two holes below line up. Is this proper use of GDT for non-opposed diameter of the same size. It has implied self-datum according to a GDT book I have but I am unsure if my interpretation is correct. Please verify. Thank you.

-Jason Nicholson

 

[MechNorth]

A couple things, Jason;
1) your tolerance is in inches (no preceding zero) while your dimension is in mm (you have inches as reference)
2) If you are using the two holes to establish a primary datum feature, then you can use such a callout, otherwise you need to reference it back to a datum(s)
3) You need a 2X indication at the beginning of the callout to establish the two holes as a single pattern.
4) you need a diameter symbol on the geometric tolerance
5) the (M) needs to be in the same box as the geometric tolerance value of "0.05" (I've added the preceding zero)

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[JasonNicholson]

MecNorth,

Per your comments, here is a 2nd attempt.

-Jason Nicholson

 

[MechNorth]

Much better. Just need the diameter symbol on the [.039] dimension. Also, that pattern of features needs to be establishing a primary datum.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[pmarc]

Jason,
Just a small addition to what Jim said:

The pattern may indeed have to be defined as a primary datum feature as long as there is a need to have other features of the cube oriented / located to it.

If, however, you want to locate the pattern from other features of the cube (like side walls, etc.), you may want to take a look at fig. 7-49 from Y14.5-2009 or equivalent fig. 5-51 from '94 edition of Y14.5. The lower segment of composite positional callout does exactly what you already have, while the upper controls location of the holes relative to other functional features. Since you have not shown on your print anything that could anyhow indicate which features serve for datums establishment, it is hard to tell whether what you currently have is a good approach.