ASME Y14.5M - 1994 - Trailing Zeroes? 2

[jmarkus]

I have read in ASME Y14.5M-1982 that trailing zeroes are supposed to be suppressed on a drawing dimension. I was told that this also applies to ASME Y14.5M-1994, but I cannot find such a reference in that version.

Are trailing zeroes still covered by the 1994 GD&T standard?

Thanks,
Jeff

 

[vriyg]

We are debating tolerance block issues and we are trying to adopt ASME Y14.5M-1994 as our drawing "language" but we encounter LOT of resistance.

First, our current tolerance block is to my opinion inapropriate. We state a default tolerance for too many cases and features (which is not the goal of a default tolerance block I think). Meaning:

Radius = +/-.015
Chamfer = +/-.015
Weld location = +/-.25
Bend radius = +/-.020
C'sk dia = +/-.015
Flat Pattern = +/-.007 (for sheet metal)
Dim .X = +/-.030
Dim .XX = +/-.015
Dim .XXX = +/-.005
Angle = +/-.5 deg

This has lead us to many interpretations (which is very wrong!) of a dimension tolerance. For example what is the tolerance applied to a Radius (R.375) specified on a Flat pattern, +/-.015 or +/-.007 or +/-.005?? Which one prevails over the other? This system was put in place by manufacturing in the past to compensate for the lack of proper tolerancing done by the engineering department. Have they re-discovered good drafting practices or just applied a quick fix but never solved the real problem? I have never seen such a tolerance block nowhere! Anyone...

Second, we are sometimes using dual dimensioning for our european customers and we know it is not covered in ASME Y14.5M-1994. If we want to be able to use decimal places for tolerancing, is it right to say we have no choice but to use "INCHES [mm]" format where metric dimensions would only be used for reference and this way follow the non-trailing zeros rule for metric dimensions? Ex.: ".197 [5]" where the tolerance would be .XXX = +/-.005 (from the tolerance block).

Third, if we say on our drawings: "Dimensioning and tolerancing as per ASME Y14.5M-1994" can we still use INCHES only?? The standard does state Metric...

Lots of questions. I will appreciate your comments.
Thanks all.

YG, mechanical designer

 

[ctopher]

If a dwg has inches and metric, I put 2 tol blocks on dwg, one for inches one for metric. "Dimensioning and tolerancing as per ASME Y14.5M-1994" is fine for dwgs with inches as primary, it is what I also use.

 

[alexit]

We use ISO2768 with fine, medium, coarse designations. This requires the engineer to think about what will be manufactured if there is no specified tolerance.

In most cases the feature is important, so you take the time to specify a tolerance...the generic block is only there for those dimensions that are not part-to-part issues (i.e. is the radii of the cute bump on the hood of my car 100% inspected at three significant digits?)

It also gives inspection dept warm fuzzy to know ALL dimensions have a tolerance to which they can inspect parts.


Alex

 

[drawoh]

Vriyg,

I strongly disagree with using dual dimensions on a fabrication drawing. Your drawing determines the acception or rejection of your part, and there can be no ambiguity. ASME Y14.5M-1994 allows for millimeters or inches as your dimension system.

I have no objection to dual reference dimensions. I have even stooped to things liks 4.76 [3/16"], when the metric dimension was a round English number.

Our fabrication block is an add-on to a standard, very simple title block. We can select a millimeter block or an inch block. This keeps things fairly simple, and it allows us to use tolerances that are approximately equivlent to each other -- .005" ~ .01mm.

I see nothing wrong with a set of standard tolerance notes. It is allowed by the standard. The effect of this is that you do not have to explicitly attach tolerances to each of your dimensions, and you save time. This is not necessarily good, since some people use the opportunity to not think about what they are doing. I am getting tired of seeing welding and sheet metal bending specified to +/-.005".

JHG