Common Centerline

Question

Common Centerline

MicroJ (Mechanical)

(OP)

4 Jun 04 10:25

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 (Mechanical) · Answer 1 · 2004-06-04 11:24:42

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 (Mechanical) · Answer 2 · 2004-06-08 17:08:14

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 (Mechanical) · Answer 3 · 2004-06-08 17:09:28

MicroJ,

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

   Drat!

                      JHG

MicroJ (Mechanical) · Answer 4 · 2004-06-09 06:44:18

RE: Common Centerline

MicroJ (Mechanical)

(OP)

9 Jun 04 06:44

Great, thanks for the help guys.

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Common Centerline