【转帖】olerance calcs

yang686526

tolerance calcs
just thought this may be helpful to any of you.
ctopher,
   you do realize don't you that the formulae for gd&t positional tolerances are very simple?  
   for a screw passing through a clearance hole into a tapped hole, the positional tolerances equal one half the diametral clearance, based on mmc values.  for a bolt passing through two clearance holes, the positional tolerances equal the diametral clearance, again, based at mmc.  
   most of the time, i do the arithmetic in my head.  without the convient tables, people might consider alternate gd&t schemes like setting the positional tolerance to zero (usually but not always at mmc), using holes as datums.
                    jhg
yes, i know. thanks drawoh.
the link is just for anyone that does not understand it and want a visual tool. just for info.
chris
sr. mechanical designer, cad
solidworks 05 sp2.0 / pdmworks 05
ctopher,
i also do the math in my head, or scratch it down with other numbers i'm working with, but this is a good tip.  the site has alot of good reference information other than gd&t.  
it's scary to think that there are people who would use those calculators without understanding what they are doing!
tunalover
i was taught to do it by hand. but, these days i hear the excuses all the time from engineers and designers that they either don't have time (too busy) or why do it if it is available online.
sometimes when i get very frustrated with coworkers, i catch myself doing the same. or sometimes if i'm rushed, i may use the online site for check.
chris
sr. mechanical designer, cad
solidworks 05 sp2.0 / pdmworks 05