×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

True Position

True Position

True Position

(OP)
Hello everyone
I am wondering about the true position diamter value. In my case I have two circle parts which has several hole and the coaxiality tolerance is very important between the holes. Please se the attach image. The hole is marked with black color.
I have add true position value for upper part (the green one) 0.2 and for the lower part (yellow one) I add the true position value 0.1. Is it correct to do that or shall I keep the same value for both part?
Between the parts pins and shaft will be placed.

RE: True Position

Quote (OP)

coaxiality tolerance is very important between the holes.

Aren't those clearance holes in the green part? Why you care so much about their alignment with mating holes in the bottom part?

RE: True Position

naah,

Your true position tolerance is a function primarily of your screw configuration and clearance.

There are instructions for calculating this in the ASME Y14.5 standard. I too have worked them out, and I have provided pictures — HTML PDF.

--
JHG

RE: True Position

(OP)
Thank you for your inputs. Acctually I am not aiming for the bolt holes. I have 3 smaller hole with diamter 1.98 mm in both part.
In the lower part (Yellow one) I used 0.05 as true position diameter and in the upper part (green) I devide the true position as 0.05/2 and used 0.025 as true position diamter.
What I am looking for is, if there is a rule of choosing or calvulating the true position diameter, when it comes parts that will make an assembly.

/NAAH

RE: True Position

naah,

It does not matter if your holes clear bolts, shafts, cotter pins or dowels. The calculations are the same. ⌀0.05mm is a tight positional tolerance. Standard practise with dowels is to make a hole to provide XY, and a slot to control θ.

--
JHG

RE: True Position

We can't talk about position tolerances until we know the datums. Are the position tolerances for each part tied back to common datums on each part?

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! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close