Tolerances block interpretation

[coax1]

Our company has established certain procedure in regard to the standard tolerance block in the drawing format. Recently, I notice that the interpretation of these tolerances is awkward.
Our standard tolerance for 3 digits behind decimal is .xxx ±.005. Occasionally we have other dimensions that required tighten tolerance such as ±.002. So, in order to eliminate repetitive ±.002 on each critical dimension, we created another standard tolerance with 4 digits behind the decimal just for the ±.002. This is how it looks now:

.xxx ± .005
.xxxx ± .0020

I think the four digits tolerance should not be mixed with three digit tolerance value. I have never seen this kind of format before. Can anyone tell me if the above format violated ANSI Y14.5M-1995 standard? or latest.

Sincerely

 

[swertel]

No, what you have there is fine since you have 4 places for the dim value and tolerance, with that last zero being significant.

If you had .xxxx [±] .002
that would be wrong.

--Scott

For some pleasure reading, try FAQ731-376

 

[coax1]

Thanks Scott

 

[jackk]

I've seen many US companies use different decimal place values to specific standard tolerances.

I've been told that US and EURO interpret decimal place numbers differently. In European countries; 0.01 means exactly the same as 0.0100, but in US the more decimal places would indicate a tighter (or more precise) tolerance (even though it's the same numerical value). Any comments?

 

[swertel]

That's an ANSI/ASME vs ISO standard. In ANSI, the trailing zeros are significant digits defining a tolerance. In ISO, they are not and are therefore excluded. Interestingly enough, ISO standard keeps the leading zeros, though, as in 0.01 vs .01.

--Scott

For some pleasure reading, try FAQ731-376