huangyhg

is this correct gd&t?
here is a copy of the print i am talking about
just taking a real quick look i'm thinking the parrallellism is unnecesary as the positional is tighter.
however others on this forum are far more experienced so can give a better answer.
gotta go...
runout would seem more correct here.
"art without engineering is dreaming; engineering without art is calculating."
how would you inspect runout on two flats? i agree, some kind of runout would be the correct callout but inspecting runout on flats???
i would also like to know if the callouts are correct. unfortunately our drafting team has little to no knowledge in the gd&t area, our quality department has all the gd&t knowledge (which is what i'm in). before i toot my horn i want to make sure i'm barking up the right tree. the callouts don't seem correct but i'm not 100% sure.
i'm thinking a symmetry callout would be appropriate?
you are showing parallelism to itself.
chris
solidworks 06 5.1/pdmworks 06
autocad 06
mopar4u,
i agree with ctopher on the parallelism. i would guess that the drafter is trying to control the parallelism of one surface to the other. if the tolerance is +/-.005", this could be out by .010". it is badly drawn.
i have no problems with the symmetry. this is described in asme y14.5m-1994 in section 5-13. the positional tolerance provides a control.
jhg

this example has some other problems i believe. the angle and the flat on the bottom are inadequately defined. if he is needing the top surface parallel to c it needs to be handled with a separate callout. curious to know that the datum feature a is.
the tp callout is okay as long as clocking is not important. then parallel to itself is wrong. does that flat need to be a datum? but your total runout is wrong. it should be just to datum -a-. also, as a side note, total runout would be an expensive shaft. i would just use runout.
one last thing to ponder when it comes to assigning datums to a part is it needs to clearly define design intent
best regards,
heckler
sr. mechanical engineer
swx 2007 sp 2.0 & pro/e 2001
dell precision 370
p4 3.6 ghz, 1gb ram
xp pro sp2.0
nvidia quadro fx 1400
o
_`\(,_
(_)/ (_)
(in reference to david beckham) "he can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. apart from that, he'
the total runout is to be checked using datum a and datum b of equal importance, hence the a-b in the frame. datum a and datum b are our bearing journals.
heckler, i agree, that parallelism callout is wrong. i guess the more that i look at it, the more symmetry seems to fit what the drafter is looking for. the symmetry callout could replace the true position and the so called parallelism. like i said, our drafters have very little gd&t knowledge.
thanks for the help everyone, great site.
mopar4u,
be careful with symmetry. it is not the same thing as parallelism. a surface profile might work too.
i suggest a chat with the designer. you need to know exactly what it is they want. we could be very confused.
jhg

__________________
借用达朗贝尔的名言：前进吧，你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]