【转帖】deveation question

yang686526

deveation question
is it acceptable practice to show two negatives in a tolerance. for example .756 -.001/-.002? thank you.
i have seen this done on manual drawings, but it doesn't meet the requirements of associative dimensioning with most cad drawings/models.  the model should represent the actual part, and such a dimension would not reflect the size of the actual hole without manually editing the dimension.
while i am unaware of any, there may be cad packages out there that will handle this type of dimensioning.
there certainly are cad systems that can work this way and it is a perfectly normal way to dimension shafts and holes.
take a look at your tolerance stackups, there may be a good reason for this.
david
ajack,
i was hoping that there was some software that could handle this (model at actual, dimension at two negative or positive limits - not actual).
there is. vero certainly does it.
inventor will allow you to do this!
david
dumb question, but "why would you want 2 minus tolerances?"  have not seen or heard of.
nominal size hole with a press fit maybe?
david
man i really opend a can o worms here. but i asked because i got a customer drawing with that double minus tolerance.and from what i have read that is acepatable in metric drawings but not is us units. thanks for all the responses.
it is certainly an iso standard.