General Drawing Tolerances
General Drawing Tolerances
(OP)
I am interested in finding out if the field is moving away from using a general, or boiler-plate tolerance block on a drawing format or if most organizations are continuing to use it. Any opinions would be appreciated.





RE: General Drawing Tolerances
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
RE: General Drawing Tolerances
People relying on MBD may be doing differently.
KENAT, probably the least qualified checker you'll ever meet...
RE: General Drawing Tolerances
RE: General Drawing Tolerances
When the people fear their government, there is tyranny; when the government fears the people, there is liberty. - Thomas Jefferson
RE: General Drawing Tolerances
Usually, tolerance blocks on drawings state that a certain number of decimal places indicate the tolerance. ASME Y14.5M-1994 states that you do not apply trailing decimals to your metric dimensions.
Most of my drawings are metric. I can use our tolerance block, or I can follow ASME Y14.5M-1994. I follow ASME Y14.5M-1994.
Going through each and every dimension on my drawings and adding or ensuring there is a tolerance easily adds around five minutes time to each and every drawing I generate. I think I have wound up with better drawings.
JHG
RE: General Drawing Tolerances
KENAT, probably the least qualified checker you'll ever meet...
RE: General Drawing Tolerances
thread1103-199111: Fractional dimensions
You may find the thread in general of interest.
RE: General Drawing Tolerances
KENAT, probably the least qualified checker you'll ever meet...
RE: General Drawing Tolerances
Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 06/08
ctopher's home (updated Jul 13, 2008)
RE: General Drawing Tolerances
BTW, even if metric is employed, title block tols can still be used. There's no law saying you can't. :) Just make a note of this variation from the standard in your own company's drafting standards. It is acceptable within ASME Y14.100 paragraph 1.2 to not use particilar sections of the ASME standards as long as you are clear as to what differences you have when this happens.
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: General Drawing Tolerances
For instance in the rest of the world, for metric fasteners, if you just put M5 it means M5 thread standard coarse pitch. In the US you're supposed to put the pitch, this caused a lot of confusion with European employees, also our CAD didn't easily comply and Americans weren't generally as familiar with metrics and it caused issues there too. To get around this we have a note saying "Metric thread callouts without a pitch specifed are course pitch" however this still seems to confuse people.
KENAT, probably the least qualified checker you'll ever meet...
RE: General Drawing Tolerances
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: General Drawing Tolerances
RE: General Drawing Tolerances
Chris
"In this house, we obey the laws of thermodynamics." Homer Simpson
RE: General Drawing Tolerances
RE: General Drawing Tolerances
What I frequently find is that people forget that the general +/- tolerances apply to non-toleranced dimensions, so they end up with +/- tolerances locating the centers of holes, rads, etc., and / or conflicting with GD&T controls. Plus, you would end up with tolerance accumulation and wedge-shaped tolerance zones.
There is a growing use of the notation that I indicated above in conjunction with the general surface profile control. It's in use already in the Big-3 Automotive, in aircraft industries, space, consumer products, and the list goes on.
IF your company's goal is to stay with 2-D drafting or using paper drawings for manufacturing, designers won't necessarily notice the difference. If, however, you are moving toward Y14.41 (digital product definition standard) then the method I've outlined is how it will be done. In fact, Y14.41 prescribes a very limited number of uses for +/- tolerances.
I've heard that the automotive & some aerospace firms are mandating the use of Y14.41 for Tier-1 within a few years, which means Tier-2 and Tier-3 will likely follow shortly after if they are allowed to lag behind at all.
Jim Sykes, P.Eng, GDTP-S
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