Previous in Forum: Mold Modification   Next in Forum: Old Lathe Manual Needed
Close

Comments Format:






Change Mode
Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







Add Vote
6 comments
Rate Comments: Nested
Dal Wagner
Member

Join Date: Jun 2011
Posts: 7

Geometric Tolerance for Large Diameter Piece

10/16/2012 9:10 AM

I'm looking for a geometric tolerance value for circularity on a two large diameter parts .I'd also like to know what the minimum taper I could achieve over the respective lengths.

I have no idea what is achievable.

The circular structures are fairly thin with wall thickness approximately 12-15mm and are supported with rings and flanges to increase rigidity. All material is fabricated steel plate.

The first part has an OD of 2378mm and an overall length of 1186mm

The second party has an ID of 2854mm and an overall length of 1191mm.

I had originally hoped for a circularity value of 0.25 but I think this is unrealistic.

Any input would be greatly appreciated
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Good Answers:

These comments received enough positive votes to make them "good answers".
PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#1

Re: Geometric Tolerance for Large Diameter Piece

10/16/2012 9:59 AM

Flangeless pipes with that sort of diameter and thickness would have difficulty achieving better than +/- 3mm or so, as:

  • on their sides they would start sagging under their own weight, and
  • the manufacturing technique (seam welding?) would introduce distortions at the weld, even if the rolling were perfect, which it rarely is.

The flanges would help, though having attached the flange would rather restrict the amount of corrective stretching the item could withstand before the bolt holes no longer line up.

__________________
 "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
2
lyn
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#2

Re: Geometric Tolerance for Large Diameter Piece

10/16/2012 12:08 PM

Look here:What is GD&T ? - Engineers Edge
Register to Reply Good Answer (Score 2)
Go to Next Good Answer
Richard R Langley
Participant

Join Date: Oct 2012
Posts: 2
#3
In reply to #2

Re: Geometric Tolerance for Large Diameter Piece

10/16/2012 1:19 PM

Very good resource, thanks for posting. Very informative.
Register to Reply
lyn
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#4
In reply to #3

Re: Geometric Tolerance for Large Diameter Piece

10/16/2012 2:49 PM

Thanks,

Hang around. There are good resources here. MatWeb is another fine site.

There are also some really sharp people here, in many fields.

Welcome to the forum.
Register to Reply
2
polymerfan
Associate

Join Date: Jun 2011
Posts: 48
Good Answers: 2
#5

Re: Geometric Tolerance for Large Diameter Piece

10/18/2012 2:35 PM

Another question that you should ask is what tolerance do you need. If you are over-specifying you will be adding cost/price unnecessarily. In the words of my design engineering professor, don't turn a 1 cent hole into a 10 cent hole (or into a 1 dollar hole) by tightening the tolerance without a reason. Only specify what is needed for the application.
Register to Reply Good Answer (Score 2)
No more Good Answers.
lyn
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#6
In reply to #5

Re: Geometric Tolerance for Large Diameter Piece

10/23/2012 10:28 AM

A belated GA for that observation. Coming from the aerospace industry I saw this all the time. Out of 50 features, maybe 5 were critical but it takes time to tolerance individual features. Not to mention the cost of inspection. rejection, material review boards to determine criticality.

The designer saves 20 minutes, but costs 10 hours of extra work down-line.
Register to Reply
Register to Reply
Have a Different Question?
6 comments

Good Answers:

These comments received enough positive votes to make them "good answers".
Copy to Clipboard

Users who posted comments:

lyn (3); polymerfan (1); PWSlack (1); Richard R Langley (1)

Previous in Forum: Mold Modification   Next in Forum: Old Lathe Manual Needed

Advertisement

Got Something to Say?
Ask a Question
Start a Discussion

Search this Forum
Manufacturing:
Go

CR4 Sections
Aerospace
BioMech & BioMed
Chemical & Material Science
Civil Engineering
Communications & Electronics
Education and Engineering Careers
Electrical Engineering
General Discussion
Instrumentation
Manufacturing
Mechanical Engineering
New Technologies & Research
Software & Programming
Sustainable Engineering
Transportation

Site Directories
Forum Directory
Blog Directory
User Group Directory
RSS Feeds

CR4 Rules of Conduct
CR4 FAQ
Site Glossary

Who's Online (66 right now)
Show Members
Advertisement