"0.50in" or ".50in" in drawings

ASME Y14.5-2009:

1.6.2 Decimal Inch Dimensioning

The following shall be observed where specifying decimal inch dimensions on drawings:

(a) A zero is not used before the decimal point for values less than 1 in.

(b) ............

But, on the other hand .........

1.6.1 Millimeter Dimensioning

The following shall be observed where specifying millimeter dimensions on drawings:

(a) Where the dimension is less than one millimeter, a zero precedes the decimal point. See Fig. 1-4.

(b) ...

Hi wingman1985,

There is no difference between "0.50in" and ".50in". It is a matter of preference. Some people feel it is proper to include the zero - "0.50in" (I am one of these people). Other, lazy people, do not choose to include it. In any case, it does not change the number of significant figures.

Mike

In my opinion, one of the biggest problems with standards is that they seldom tell the rationale behind them. Admittedly this has the advantage of shortening the documents, but it is irritating when no explanation is given for counterintuitive provisions.

I like the leading zero, as in the mm standard. I wonder why the ASME standard omits it. A leading decimal point might be obscure, especially in hand-written dimensions. Leading with a digit should make this less likely.

During old school days we were taught about this aspect. We were told that the decimal should never be the left most character.

The reason was simple

It is possible to misread .50 as 50

However one does not misinterpret 0.50 as 050 or 05.0 since in either case the leading zero shouldn't have been there.

It also may be noted the slight space created by the decimal character, which will be negated in case it is left-most or right most (where it does not matter anyway)

This was later extrapolated into scientific notation where the decimal should exist after the leftmost significant digit.

People may be reluctant to write 0.50 as 5.0E-1 though.

Why ASME has given that notation I am not sure, may be just to maintain it's identity/ difference , as I have seen in quite a few ASME standards where logics fail., _{(and without being biased, it does exist in ISO too)}

GA and congrats on your 100th!

Thanks. Maybe I can get the mods to promote me to 46 now.

ANSI/ASME Y-14.5 as well as DoD MIL-STD-1000 Used to require the use of the leading zero in order to make sure the decimal point is indeed a decimal point and not a speck of dirt or other inadvertent mark. Frankly they are idiots for removing the requirement. Also the number of digits behind the decimal point is important as it defines the tolerance allowed for that dimension. it also requires that all decimal points use a period, not a comma. You Europeans take note Commas are NOT TO BE USED FOR DECIMAL POINTS.

Yes, this IS a translator's job to know.