Controlled radius Simliar or to on a diameter. 4

[SDETERS]

Please see pic. What I am after is a way to control a profile within the tolerance zones shown. The feature that I am after is on the left. The Feature on the right is what I do not want, which is the surface that has reverse of surfaces or sharp points. The Left feature I get when I use a boring bar to machine the bore and the right surface I get when I machine the same bore with the reamer. The reason for the difference is due to an interrupted cut during the boring/ reaming process. I am looking for a good way to call this out on the print with GD&t or some other way. We are using ASME 1994 standard.

Thanks

Shane

 

[SDETERS]

I am sorry my first attachment does not seem to work Here is a JPEG.

 

[SDETERS]

One more time I had a bad character in the name.

 

[MechNorth]

A size tolerance allowing the inner & outer boundaries, with a form control (cylindricity) refinement would be my first thought, but you actually have a better form error on the RHS. An adequately tight form control would eliminate much of the jagged aspect of the RHS, and still prevent ehe ellipsing of the LHS. What is it about the RHS that bothers you?

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[SDETERS]

We are pressing a bushing into this bore. We have found if the points around bore makes the press in force light versus the nice oval shape which makes the press in force higher which we are wanting. Thanks for the feed back

 

[MechNorth]

Ah. Okay, you are using bad manufacturing to your advantage. The problem is, it's not controllably/repeatably 'bad'. You are better off restricting the size tolerance to a more precise range that will ensure the press fit you seek. Chances are that when you get to that tighter size tolerance, you will not need a form refinement.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[ak762]

I would consider also that there is relationship between precision of fit grade and surface roughness

 

[Belanger]

Maybe some sort of "rate of change" circularity tolerance? Consider how we can do this for flatness (a larger flatness overall, but then a smaller localized flatness tolerance), and maybe try to extract the same idea to a double-decker circularity callout.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

http://www.gdtseminars.com

 

[MechNorth]

I don't see any reason that wouldn't work, J-P. As always for a novel situation, it's not directly supported in the standard, but it seems at first glance to be a reasonable extension of basic principles.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[pmarc]

I agree that something like circularity per unit of perimeter length could work as a logical extension of principles.

In fact I think that concept of "controlled diameter" (as an extension of "controlled radius") could easily fall under that category too. This would most likely have to be done by placing additional note - as there is obviously no standard symbol for controlled diameter - but I do not see any major roadblock that would prohibit such practice. On the contrary, this could be quite interesting and useful idea in case of sealing surfaces for instance, where any abrupt changes in outline's form may significantly reduce sealing efficiency.

However in OP's case it seems to me, as Jim already noticed, that it is not the matter of feature's form error, but of properly defined size tolerance. Shane, would you have any issues with sharp points and reversals if the actual diameter on RHS picture was close to outer tolerance limit all around? Is there any other reason, beside poor press-fit, that makes RHS picture unwanted?

 

[SDETERS]

On the RHS it all has to do with Surface area and contact with the Bushing I do believe. It is the sharp points that is giving us trouble. This is all about press in force and press out force on this bushing. We have the size controls at the limit of what the manufacturing guys can hold in our machines at this time. Doing what you said about circularity with a length or per a certain angle of degree does makes some sense. This has been discussed in house but I did not see this in the standard. But I do not see no reason why something like this could not be put on the print. What is good about this issues is that the machining of this bore is done in house, so we can come up with a callout and come up with a company standard on how it should be inspected per the callout on the print. Thanks for all the feedback.