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

 

[GDTGUY]

I assume that you are referring to the paragraph that addresses the interpretation of limits. In ASME y14.5M-1994, this is paragraph 2.4 (page 25) and reads:

"All limits are absolute. Dimensional limits, regardless of the number of decimal places, are used as if they were continued with zeros.

EXAMPLES:
12.2 means 12.20.....0
12.0 means 12.00.....0
12.01 means 12.010....0

To determine conformance within limits, the measured value is compared directly with the specified value and any deviation outside the specified limiting value signifies nonconformance with the limits."

Hope this is helpful

GDTGUY

 

[jmarkus]

Actually I am referring to the requirement that if a dimension is 10.0 it should be shown only as 10, but if it is 10.5, the decimal is shown.

I discovered I was comparing Y14.5M-1982 to Y14.5.1M-1994. I was supposed to look in section 1.6 of Y14.5M-1994. But I'm good now that I have figured it out.

Thanks,
Jeff

 

[looslib]

Just to set the record straight, you are only talking about metric dimensions.

Metric dimensions do not use trailing zeros to hold decimal places for tolerancing, English dimensions do. This has caused us a lot of problems with the default tolerance block on our drawings. There is an exception when using bi-lateral or limit tolerancing.

Metric dimensions less than 1, use a leading zero, English dimensions do not.
Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[gearguru]

Some US car makers standards require to use 0 (zero) in metric dimensions, does not mater that they are not significant. It makes no sense, but they want it. The reason is unknown. Therefore - we put 10.0 for a 10 mm dimensions...
gearguru

 

[looslib]

My guess is just what I explained, they want the trailing zero's to designate the default tolerance for the dimensions.

How do you tell the difference in a metric drawing and an inch drawing if they all have trailing zeros?
Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[PUTTER]

The standard for dimensioning is that the dimension and the tolerance on that dimension must contain the same number of decimal places. So the issue of trailing zeros, is a not a concern as long as the number of decimal places for the dimension and tolerance are the same. Example: 2.35+/-.010 is not correct, it should be either 2.350+/-.010 or 2.35+/-.01, with the latter preferred. Same guidelines apply to metric dimensions.

 

[luftbar]

Very helpful discussion on zeroes and significant figures. Question: when we measure tubing dimensions and a spec is 2.56 at a limit does the ANSI standard force us to reject a measurement of 2.562 and not allow us to round it off to 2,56? That is does all industry adhere to the continuation of dimensional specs with zeroes and does all industry therefore ignore rounding off to significant figures?

 

[looslib]

What is your tolerance on the 2.56 dimension? That will determine if the 2.562 measurement is good. Since you have rouded off the dimension to 2.56, the least amount of tolerance you could have, ignoring unilateral, is +/-.01. Therefore any measurement between 2.55 and 2.57 is good.


Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[drawoh]

Here is what ASME Y14.5M-1994 says...

1.6.1(a) Where the dimensions is less hthan one millimeter, a zero precedres the decimal point.

1.6.1(b) Where the dimension is a whole number, neither the decimal point nor a zero is shown.

1.6.2(a) A zero is not used before the decimal point for values of less than one inch.

1.6.2(b) A dimension is expressed to the sam number of decimal places as its tolerance.

On English or metric drawings, you can have a note indicating a tolerance for a given number of decimals. It is the note on the drawing that makes the decimals significant.

JHG

 

[gearguru]

PUTTER:
You have to use the zero before the decimal point with mm dimensions. Your example has only one correct answer: 2.35+/-0.01
optech is right, standard does not ask for trailing zeroes.
But as I mentioned, some car makers insist on it. I still believe that it does not make sense. We do not make shafts 50 inches diameter for cars here; we also dutifuly state in the title block, that the drawing is metric (which is the standard for the US auto industry) so there can be no mistake if we do not use nothing meaning zeroes.
gearguru

 

[procadman2]

ANSI Y14.5M-1994 has caused a great deal of changes with the respect to trailing zeroes in dimensions.
Prior to the 1994 revision it was common to list default tolerances in the title block of a drawing or at least a reference to some company document/mil or sae std showing these references. ie: x.xx = +-0.01 x.xx =-0.005
etc.
I've been back in the aerospace (NASA Contractor) field for 4 weeks and -1994 has made it very messy.
Using the -1994 std and Proe software there are NO TRAILING ZEROES.
The title block has a multiple tolerancing area with a designation of fine, medium and coarse. The engineer is supposed to pick one of these and note it on the drawing.
This is hopefully the worst example.
Coming from a machining/manufacturing background and an ME and 25 years in the business I still cannot understand any benefits. If anything, this section of -1994 has made it more difficult to state individual tolerances.
The only other option is specifying a tolerance on each dim whether by +- symmetricaly or by limits. Both of these options lead to further errors and do not contribute to a clean drawing. (This stands true for 3D models as well.)
I can offer no suggestions or remedies.
Until I see other evidence my opinion of this section of -1994 was rather poorly researched and does not add to ease of manifacturing or engineering.
I will be happy if someone has a better answer.
procadman2

 

[swertel]

Our answer was to make our company standard -1982. The ONLY times we use -1994 (being a government contractor) is if our customer DEMANDS it per contract. Usually, these contracts are the ones were the customer takes ownership of the drawings once the design is complete. If we maintain the drawings -1982 all the way!

 

[looslib]

What am I missing.

I compared section 1.6 Types of Dimensioning in both the 1982 and 1994 standards and they are worded the same.

Maybe if you go back to the 1978, I think it was, standard, section 1.6 might be worded differently.


Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[procadman2]

GDTGUY et al.

With -1994 and no trailing zeroes how do you establish simple dimensional tolerances? ie: +-0.01 +-0.001 +-0.0001 etc

procadman2
Proe Design & Admin
Mechanical & Aerospace

"You can't build a reputation on something you haven't done."
H Ford

 

[looslib]

You have to specify it on each dimension that requires a non-generic tolerance. Also note that the no trailing zero requirement is only on metric dimensioned parts. You can still have a title block tolerance block for those dimensions that are designed to a precision that they have a non-zero value.

If I have a tolerance block that says:
X/X.x +/-3
.xx +/-1.5
.xxx +/-.8

and I have the following dimensions:
12 5 5.5 4.25 5.135

These all fall under the tolerance block tolerance allowance (except hole diameters, which is another story.)

If I want the 5.5 to be tighter I have to specify it as
5.5 +/-.8 or 6.3/4.7.


Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[procadman2]

So, the consensus is -1994 requires us to specifically tolerance each metric dimension.
I see this as yet another reason for people, stuck in 1942, to not use metric.
But, for the rest of us, I assume we are stuck with either adhering to or ignoring this section of -1994.

I am currently talking to Paul Drake, author of Dim & Tol Handbook (McGraw Hill) about this issue.
I will post my findings.

Thanks for the help.


procadman2
Proe Design & Admin
Mechanical & Aerospace

"You can't build a reputation on something you haven't done."
H Ford

 

[procadman2]

Gentlemen,

I talked with Paul Drake (author of Dim & Tol Handbook (McGraw Hill)).

His suggestion is to use the same general tolerancing method as we always have and ignore the trailing zero rule.

He is going to attempt to get this clarified in the next ANSI Dim & Tol edition. (Due out soon). Hopefully this rule will either be omitted or they will have a method of general tolerancing other than limiting every dim on the dwg.

procadman2
Proe Design & Admin
Mechanical & Aerospace

"You can't build a reputation on something you haven't done."
H Ford

 

[looslib]

Except that our drawings all have in the titleblock "Drawn In Accordance with ANSI Y14.5-1989" (or ASME Y14-5-1994).



Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[procadman2]

I understand.

I am in the same boat. (and it's starting to sink.)

I was told that after the switch from Autocad to Proe the designs took 3 times longer to do.

This is just one of the many reasons. It has nothing to do with the ease of use of the software package. It is mostly caused by standards being in place before they are completely thought out. Because you cannot fudge things in a parametric document it takes several times longer to complete.

Hopefully this will change soon.


procadman2
Proe Design & Admin
Mechanical & Aerospace

"You can't build a reputation on something you haven't done."
H Ford