Greg Rupp

Proper dimensioning

Discussion created by Greg Rupp on Jun 26, 2008
Latest reply on Jul 1, 2008 by Jerry Steiger
I must be having an off day, but I could use some help. I have a very plain U-channel piece. It's bent out of .1046" sheet metal and is 2.500" OD across the flanges that are equal length (6.00").

It's my understanding that when you dimension across two bends, which are assummed to be bent at 90° (undimensioned), that that dimension is carried all the way down the part. So, my part is dimensioned 2.500±.015 across the flanges and i would assume that diminsion would be held at the bend and on the open end. My vendor is saying they can only hold that at the bend, which I'm perfectly fine with, but then how do I properly control the dimension on the open end of the u-channel.

Secondly, our standard tolerance block say the tolerance on a bend is ±0.5°. Because the flange is 6.00" long, that would techically allow the flange to be .052" off the true position. So which dimension trumps. keep in mind the 90° isn't actually diminsioned, but just understood.

This image might help.

Thanks for review this post!