×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Hole Tolerance Question

Hole Tolerance Question

Hole Tolerance Question

(OP)
Hello,

I am trying to perform a tolerance stack up on a small assy. I have:

Block w/ Hole ID - 0.309 +/- 0.002
Bushing OD - 0.307 +/- 0.005
Bushing ID - 0.250 +/- 0.005
Pin OD - 0.244 +/- 0.002

I want to put the bushing into the hole and put the pin into that. I have never done a tolerance stack up on anything except examples (none of which I had anything like this).

Right now, my idea is to cut it in half and just do half of the stack up so it represents a more simple stack up.

Could someone give me direction on how to do this?

Thanks,
J

RE: Hole Tolerance Question

Sorry, what are you trying to analyze?

Worst case fit of the bushing into the block is minimum block hole dia - maximum bushing OD. So .307-.312 so .005 interference - which may be a bit aggressive depending on factors you don't list.

Likewise Min bushing ID -max pin OD. So .245-.246 = .001 interference which again I don't know if that's appropriate for your application or not.

If you want to find max slop then do the opposite calculation.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Hole Tolerance Question

What kind of fit are you interested in? Clearance fit, press fit, transition fit?
Right now it seems that all fits are transition. You just need to compare:

#1:
a) min. ID of hole with max. OD of bushing;
b) max. ID of hole with min. OD of bushing;

#2:
a) min. ID of bushung with max. OD of pin;
b) max. ID of bushing with min. OD of pin;

In both cases there will be an interference in a)'s and a loose in b)'s, so this is typical transition fit.

RE: Hole Tolerance Question

(OP)
Hey,

My question was not using worst case, I figured that out. I was wondering if I was using the RSS, more specifically if it was okay to take off from the outside to the center and then just double everything to get the entire hole tol.

Thanks,
J

RE: Hole Tolerance Question

Right off the bat I can see that the bushing can be anything from a .005 press fit to a .005 clearance fit. It seems that a design should require one or the other, but not either one. This makes a difference in how the rest of the stuff stacks up. Can you re-evaluate and let me know if that was your intent?

Powerhound, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Hole Tolerance Question

And what does it have to do with RSS?

RE: Hole Tolerance Question

(OP)
To clarify - The bushing design was just changed. We are switching to a plastic bushing with a slit in it, so it can fit a range holes, it has a .035" slit in the side and now has a .315" OD with and ID of .258 +/-.005 on both OD and ID.

With that said, it will fit down to a .305 hole if my math is correct, before that gap closes. Thus making it a slip fit all the time.

My asking for the RSS tolerance stack up is mearly because I am not sure if my method of doing this (in this scenario) is correct and I wanted to see if someone could tell me if my method works.

WC right now, I believe will have a .006" press fit. I would rather it be slip fit because we are putting a rivet (the pin) through the center and right now I am not sure how much that will expand.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources