×
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

Stack up Tolerance Analysis.

Stack up Tolerance Analysis.

Stack up Tolerance Analysis.

(OP)
What is the calculation needed to do a Stack up Tolerance
Analysis.Never done it before.
I have a part in a "U" shape with a hole pattern of 20 holes
and a couple of slot on the sides.
Tolerance is off by .001" in one side of the hole pateern and on one slot.
Any ideas?
Thank you.  

RE: Stack up Tolerance Analysis.

thread1103-229607: Using spreadsheet for Tolerance Stackup
thread1103-139353: dimensional stackup
thread2-188871: Stackup Tolerance Study.

Simplistically you add all the contributing dimensions and the tolerances to get the overal dimension and tolerance.

If the above links don't help come back with a diagram of your particular situation and someone may be able to give a more targetted respons.

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: Stack up Tolerance Analysis.

rmaki,

   Tolerance off by only .001"?  Sounds like a pretty accurate hole pattern to me!

   Tolerance stack up is an assembly analysis for evaluating tolerances on your drawings.  It is a useful process for designers and design checkers.  It sounds like you are doing inspection.  What do you want to accomplish?  

    If you insist on your screws and bolts passing through clearance holes without interference, check out the appendices of ASME Y14.5.  My website at http://home.eol.ca/~hgibson/tolerances, covers some non-GD&T techniques, especially helpful if you were not the one who generated the drawings.  

   If you need to position components, you need to do algebra and arithmetic and then add and subtract tolerances.

   If you have chain dimensions on a single part, you can do a stack-up analysis, or you can re-draw the part and apply tolerances correctly.   

               JHG

RE: Stack up Tolerance Analysis.

(OP)
Thanks for the reply.
Drawoh, all the holes on the left side are off (10)plus one slot.
Looks like the set up was move on the CNC operation.
  

RE: Stack up Tolerance Analysis.

Hi rmaki

What is the allowable tolerance for the holes to be off nominal?
To do a tolerance stack you need all the relevant drawings which fit into the particular assembly, then you put the tolerances on each component max or min and assuming the components are made to max and min check wether the assembly can still go together.
What I usually do is mark up a print in red of the assembly with max and min dimensions as this helps me visulise what I am checking.
To be honest tolerance stacking should be done as part of checking drawings before parts go for manufacture and should be as mandatory as putting dimensions on drawings.

desertfox

RE: Stack up Tolerance Analysis.

Quote:

To be honest tolerance stacking should be done as part of checking drawings before parts go for manufacture and should be as mandatory as putting dimensions on drawings.

Go on desertfox, tell another one, I needed a good laugh.

 

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: Stack up Tolerance Analysis.

Hi Kenat

Glad it made you laugh, I said it tongue in cheek but I meant it lol.

RE: Stack up Tolerance Analysis.

(OP)
Tolerance is +/-.0005".

RE: Stack up Tolerance Analysis.

Hi rmaki

So the parts out of tolerance and therefore should be rejected, however what are the holes for and what does the part actually do? can you upload a drawing of the part?
If you can provide more information then we might be able to help further.

desertfox
 

RE: Stack up Tolerance Analysis.

(OP)
Sorry, no DWG.
The holes are mounting holes.   

RE: Stack up Tolerance Analysis.

Hi rmaki

What are the holes for dowels, bolts, screws ? if there for bolts then the 0.001" tol is a nonsense, can you but more explicit.

desertfox

RE: Stack up Tolerance Analysis.

(OP)
Believe me, makes perfect sense it is for a Navy program.
More like a press fit,mounting holes.

RE: Stack up Tolerance Analysis.

Hi rmaki

Okay so how would you like us to help you.

desertfox

RE: Stack up Tolerance Analysis.

(OP)
We want to establish the proper approach for the repair (we still don't know if it's allowed).
It's seems that the holes are shift unilaterally may be .0002" to .0003" on the x axis.
 

RE: Stack up Tolerance Analysis.

Hi rmaki

With the information you have provided so far it would be easier extracting teeth from a sabre tooth tiger and there extinct.

desertfox

RE: Stack up Tolerance Analysis.

Quote (rmaki):

We want to establish the proper approach for the repair (we still don't know if it's allowed).
It's seems that the holes are shift unilaterally may be .0002" to .0003" on the x axis.

   We do not understand what your assembly has to do.  If you have a component that must be located within Ø.001", your part is scrap.  If the drafter ought to be horsewhipped and bludgeoned as per TheTick's recommendations in some other posts, you can review the actual design requirement and update your tolerances to something looser than what you fabricated.  

   Is your organization the fabricator or the designer?
 

               JHG

RE: Stack up Tolerance Analysis.

Hang on

First time he was saying holes are off by 0.001" and tol was .0005", now he is saying holes off by 0.0002" to 0.0003"
so now the holes are in tol?????????????.
Unless you can provide some more information we cannot help you further as the information you have given so far is insufficient

desertfox

RE: Stack up Tolerance Analysis.

rmaki,
Are you really asking how to stack the allowable position tolerance of a hole with the allowable datum shift? That woud be a more explicit question then simply asking how to do tolerance analysis in general.
Tolerance analysis can be a feature to feature analysis, an allowable location like it sounds like you are asking, upwards to an entire assembly of components.

I think this is why some of the replies are a bit on the humpor side.  But if you are just wanting to know how to stack allowable tolerance on a feature based off of datum features of size specified at mmc, there is an answer. Unfortunately, way difficult to explain in this forum for a "pattern" of features of size. For a single feature, not so difficult, but for a pattern? I have found only 1 software application that can verifiably do that right and its no spreadsheet. And there are CMMs that when correctly programmed that can do it. But in an open set-up? Go to functional gaging.

Norm

Norm Crawford
GDTP-S
Applied Geometrics, Inc.
www.GDandT.com

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