Sig Figs and Tolerance
Sig Figs and Tolerance
(OP)
Settle an arguement...
There is a dimension of 6.7mm +/- 0.25mm
Ignoring the sig figs in the dim the limits should be 6.95 and 6.45 however since the dim only has 2 sig figs the limits are 6.5 and 6.7. Agreed?
Now what if you have multiple tolerance? Do you round the tolerance (e.g. the tolerance become +/- 0.3mm) and apply it to all the dims or do you add them all up and THEN apply the rules of rounding. (e.g. 2.0 + 2.0 +2.0 = 2.25 + 2.25 +2.25 = 6.75 = 6.8?)
Thanks,
Sean
There is a dimension of 6.7mm +/- 0.25mm
Ignoring the sig figs in the dim the limits should be 6.95 and 6.45 however since the dim only has 2 sig figs the limits are 6.5 and 6.7. Agreed?
Now what if you have multiple tolerance? Do you round the tolerance (e.g. the tolerance become +/- 0.3mm) and apply it to all the dims or do you add them all up and THEN apply the rules of rounding. (e.g. 2.0 + 2.0 +2.0 = 2.25 + 2.25 +2.25 = 6.75 = 6.8?)
Thanks,
Sean





RE: Sig Figs and Tolerance
RE: Sig Figs and Tolerance
No. Based on the stated assumed limits, you would be rejecting good parts. If ±.2mm was the design intent, the drawing should state such.
I agree with TheTick.
When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - Thomas Jefferson
RE: Sig Figs and Tolerance
Significant figure are irrelevant here. ASME Y14.5M-1994 requires that you delete trailing zeros from your dimensions. In any case, the 6.7 is a requirement, not a measurement. Significant figures apply to measurements.
JHG
RE: Sig Figs and Tolerance
Can't recal the exact reference but probably somewhere like ASME Y14.5M section 1.6.1
KENAT, probably the least qualified checker you'll ever meet...
RE: Sig Figs and Tolerance
RE: Sig Figs and Tolerance
However, off the top of my head I don't know what ISO may say, but I'd expect similar.
KENAT, probably the least qualified checker you'll ever meet...
RE: Sig Figs and Tolerance
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Sig Figs and Tolerance
RE: Sig Figs and Tolerance
Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca
RE: Sig Figs and Tolerance
You are hijacking this thread. :) Anyway, I do think your point was covered above in part. Again, there's no law about this and as long as rules are established in advance, a company can choose to use .xxx .xx style dim'ing for metric.
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group