Common Centerline

[MicroJ]

Is there anything in ASME Y14.5M-1994 that defines tolerances on "common centerlines". We have a customer that frequently shows features on the same centerline w/out giving a positional tolerance...is there a default per the ASME spec ?

In the past, our method of manufacturing has insured that these features are within a range that I personally know will work for the function of the part, but we are starting to take on parts where I do not have such a luxury of knowing the part function.

 

[ctopher]

A centerline is the center of the part or feature. Having a feature on that centerline uses the tolerance from the feature the centerline is used from. Adding a positional tol could be confusing to a machinist. I hope I was clear. This was from my GD&T instructor a few years ago.

 

[drawoh]

MicroJ,

There is a default. The allowable error is zero. On your own drawings, you may explicitly apply a positional tolerance of zero.

The resulting hole must fall without the maximum and minimum material conditions of the features, such as the max and min diameters of a hole.

My GD&T instructor did not mention anything about this confusing machinists. One of the advantages of GD&T is that you can apply positional tolerances to non-dimensioned features.

JHG

 

[drawoh]

MicroJ,

On paragraph 2 above, I said "without". I meant "within".

Drat!

JHG

 

[MicroJ]

Great, thanks for the help guys.