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Detail with pilot hole to Assembly to Installation holes requirements?

Detail with pilot hole to Assembly to Installation holes requirements?

Detail with pilot hole to Assembly to Installation holes requirements?

(OP)

Hi,
I have a detail part with 4 pilot holes .128-.132dia with a pattern location of .0560M|A|B|C and hole to hole of .0140M|A. The bracket detail will be installed on the 2 longerons assembly upper and lower as shown in the picture. ME want the 2 hole to be pre-drill with .128-.132 on the longerons assembly upper and lower. The longeron upper and lower will be install to the skin using 4 pilot holes of .1280-.1320dia with a pattern location of .0140M|A|B|C. The bracket will then be drill full size drill .1640-.167 prior to fastener installation 5/32dia. What tolerance should I use at the longeron assemby? How do I ensure that the bracket holes will always matches at the installation? What step should I take to approach this problem? I am thinking to use same positional tolerance as the detail bracket.

RE: Detail with pilot hole to Assembly to Installation holes requirements?

Picture didn't get attached. But a quick read of your question makes me think that "virtual condition" will be an important part of the answer.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

RE: Detail with pilot hole to Assembly to Installation holes requirements?

(OP)

Hi Belanger,
How do you add picture in the attachment. When I click on attachment below nothing happen? I am reading about virtual condition and I have found 2 the virtual size of the pilot hole to be one to be .128+.0140=.142 for hole to hole and perpendiculariy relative to datum A and .128+.054=.182 positional tolerance relative to datum A|B|C. What should I do with this number?

RE: Detail with pilot hole to Assembly to Installation holes requirements?

You're right -- it looks like they've changed the format for posting replies. It used to have a different "look." I'm not sure how to attach!
For holes, the virtual condition is a subtractive formula, so it's not .128+.0140 but rather .128-.0140= .114 and the other one would be .128-.054= .074. But there's a lot of info in the original question and I'm not quite able to digest it all :)

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

RE: Detail with pilot hole to Assembly to Installation holes requirements?

(OP)
kenat,
The holes from the channel will be match drill on the assembly. Using the 2 Da holes on the top assembly and 2 Da holes on the bottom assembly. How to make sure that the holes pattern from the detail will matches on the assembly?

RE: Detail with pilot hole to Assembly to Installation holes requirements?

Something to do with getting the datums aligned or a common datum structure? From there you can analyze the tolerances.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

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