Detail with pilot hole to Assembly to Installation holes requirements?

[hengone]

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.

 

[Belanger]

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

 

[hengone]

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?

 

[Belanger]

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

 

[hengone]

Jean-Paul,

Attached is a picture of the assembly I was referring on my original post. Detail part is release and I am working on assembly.

 

[KENAT]

Are you saying you're going to be match drilling?

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[hengone]

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?

 

[KENAT]

Sorry hengone, I'm still having trouble working out exactly what it is you're trying to do.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Belanger]

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