How do you correctly call out coaxial holes that need to be inline so that a bolt could go through 2

[eeyew]

I'm attaching a sketch of a situation that I'm encountering where I need to make sure that the co-axial holes on a clevis remain inline after the stamping is complete. The holes are done at the last stations and I need to be able to locate both holes correctly so that I will be able to get a correct length on the assembly equipment. I don't believe the datum scheme lends itself well to control and gage R&R but this is all I have to work with.

Please let me know if I'm calling out the datums correctly and the datums are set to what I'm trying to achieve and to let me know if the composite position tolerance I have there is called out correctly and will locate this hole at a distance away from the cylinder and inline with each other.

Thanks for everyone's help.

 

[ewh]

It would be 1X and treated as a single feature, if I'm not mistakesn.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[randy64]

ewh, by "single feature" does that mean the "soda straw" diameter that is defined by the tolerance in the FCF extend from one surface to the other, or does each hole have it's own "soda straw" diameter?

In other words, is the tolerance diameter projected across the entire length of the ceneterline of the holes, or is each hole measured independently?

 

[eeyew]

I made some corrections to the markup as I had some circular referencing of datums which I'm not sure is legal to do so. Instead of I've changed datum A into a flatness call-out since I'm most interested in coplanarity with this and I changed the profile tolerance of datum C to get rid of the datums as I'm most interested in fixing that area so that I can locate the holes. Please let me know if this makes sense to what I am interested in getting

 

[pmarc]

eeyew,
Datum features of the part should be selected based on mating relationship of that part with other components in assembly. When you look at datum features you have selected, do you think these are the features that play the most significant role in locating/orienting this part in the assembly? That is the first question. The second question is: what is the precedence of datum features? Is surface A really a better candidate for primary datum feature than diameter B? Another question, if the part is subject to free state variation (which seems to be the case here), perhaps it would be reasonable to inspect it in a restrained condition (a condition that would simulate forces/deflections happening in real assembly)? As for B referenced at MMC/MMB, does that mean the dia. 50.6+/-2 cylinder is mated with a hole of dia. 52.6 min?

You are correct that your previous pictures showed circular referencing of datum features. The problem with your latest sketch is that datum features A, B and C are not controlled relative to each other at all. If A is trully a primary datum feature, B secondary and C tertiary, the datum feature B should be controlled for perpendicularity relative to A, and the datum feature C for profile relative to A|B. As long as there is no relationship between datum features defined on the drawing, the drawing is incomplete.

Regarding some other comments made in this discussion:
- Using a radial leader to indicate the diameter of in-line holes will not introduce anything new to the definition. Both methods - the one currently shown in the sketch, and the method with a leader - are legal ways to define the diameter of in-line holes. What is missing is the diameter symbol in front of both tolerance values in composite position FCF.
- <CF> modifier will turn two independent holes to a single feature of size. This means that hole-to-hole relationship will be controlled by the MMC envelope of dia. 18.30 that neither of the holes will be allowed to violate (this virtual envelope is common for both holes). Current sketch allows axes of both holes to be offset 0.6 max relative to each other, as defined by lower segment of composite FCF. This offset will be limited to 0.1 max, if <CF> modifier is used.

 

[Tunalover]

ewh is correct. The two holes would act as a single hole and would thus be a 1X multiplier. I can't think of a more straightforward way to control the coaxiality of the two holes but to declare them as a single feature with the CF symbol. Composite tolerancing would not be required. A single segment positional tolerance feature control frame would be all that'd be required. It simple and straightforward.


Tunalover

 

[lwealing]

eeyew,

Please also note that use of CF symbol is only allowed per the ASME Y14.5-2009 standard where it was introduced. If using the 1994 (or prior) standard, other methods will need to be used to define the two surfaces as a single feature.

 

[greenimi]

Obviously there are multiple ways to skin the cat. And pmarc hit the nail in the head: how this clevis works in the assembly?

Usually there are 2-3 ways to *correctly* --functionally- define a product.
Not 50 ways and “probably” not a single way!
Just my opinion.


I found on Tec-Ease *ONE* way to define *A* clevis.

The shown clevis may not work/functions in the same way as the OP’s clevis.

Hope this helps more than confuse

 

[greenimi]

http://www.eng-tips.com/viewthread.cfm?qid=317285

eeyew,
You can also read the above thread/link. 4 cases of clevis are discussed (at least in the begining of the thread)