Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Tolerance a profile to become a fit

Status
Not open for further replies.

UGMENTALCASE

Aerospace
Oct 10, 2011
123
Good afternoon, back again with my stupid but necessary questions! :)

We have some pins which are shown on the attachment, these fit into a bush head, shaped the same way (so the bush is slotted) How, or should I say what is the best way to tolerance this piece in order to give it a H7 g6 type fit with the bush? I've never done it before, as you normally put those sorts of things on a hole/shaft. I've experimented with line profile etc. but it just doesn't look right.

Any help would be great!
Cheers
 
 http://files.engineering.com/getfile.aspx?folder=e3b08798-b707-458f-8916-1a664b926cb2&file=example.jpg
Replies continue below

Recommended for you

For pins in slotted bushings, typically diameter control is all that's required to meet the majority of the function. The straightness of the pin will further secure function and prevent lack of fit.
 
I don't quite understand your picture.

Do both your pins and your matching slots have obround shape?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 
Yes checkerhater, they are both that shape. So the image is the pin part and the Bush is the female of that shape
 
First, to get our terminology straight.

According to the text of the stahdard, "For the purpose of ISO 286, only features of size type cylinder as well as type-two parallel opposite surfaces, defined by a linear dimension, apply."

That is, only simple features are subjects to "fit" and not compound ones. So, the best you may expect, is fit similar to H7/g6

H tolerance zone is extending from theoretically exact Nominal (formerly BASIC) feature into the body of the part, similarly to Unilateral profile.

g tolerance zone goes even further into the body of the part, being unequally disposed, but in the same direction - the condition that is not very well defined for Profile tolerance.

If you are willing to go there, we may consider the possibilities.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 
I think I get what you are saying :)

I was thinking of using, although didn't think it 'looked right' the profile of a line and having the tolerance one sided with the 'U' and using a mid range tolerance of the fits. So for example it would look like the attached image, being mid range of a g6 fit. You know? At least that way I know it's all going one way, and then I BASIC all the dimensions in question?
 
 http://files.engineering.com/getfile.aspx?folder=8d6aa892-52b7-4915-afba-ac819684468b&file=tol_box.jpg
It could be profile of a surface, this way the form will be controlled.
Adding datum(s) will also control orientation and location.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 
Status
Not open for further replies.

Part and Inventory Search

Sponsor