Kelvin Mount Positional Tolerance 1

[KENAT]

I’m currently checking the drawing of part of a Kelvin Mount, a type of kinematic mount (see figure 3 of this doc to get some idea what I’m talking about

http://www.optics.arizona.edu/optomech/references/papers/Lake 2000.pdf

)

Specifically I’m looking at the conical hole (like a countersink) and the V groove. In my case the V groove is of finite length with fully rounded ends.

At present the V groove is dimensioned by having the length of the parallel portion given, the included angle and the depth. The conical hole is dimensioned by the angle and depth.

I want to control the location of the features, probably using positional.

However, normally to use positional on these types of features I’d be dimensioning the conical hole by diameter & angle (ASME Y14.5M-1994 fig 1-38) and apply the positional tol FCF to the diameter and for the slot I’d dimension by overall length and width (fig 1-27) and apply positional FCF to both length and width, probably with boundary (fig 5-47).

Given the application dimensioning the depth rather than the diameter or width kind of makes sense, although if you do it right I suppose you could dimension the other way with the same results.

So is there an easy way to apply the positional without changing the dimensioning scheme? Can I put the FCF on the depth? This looks odd but is kind of equivalent.

Also given that in this case it’s the length of the parallel portion of the slot that’s important should I leave the slot dimensioned as is or change to overall length?

Anyway I’m in above my head and would appreciate any guidance.


KENAT, probably the least qualified checker you'll ever meet...

 

[powerhound]

KENAT,
I would use "profile of a surface" considering that it appears that you are not really dimensioning features of size. I would suggest using basic dimensions to define your true profile and using "profile of a surface" to apply the tolerance. See if this link helps

http://www.tec-ease.com/tips/february-07.htm

Although the scenario is not exactly like yours, it gives an example of how to dimension an angled slot correctly. It may give you a shove in the right direction.

Powerhound
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[KENAT]

Thanks Powerhound, I started to think about profile of a surface, especially depending how critical it was for function etc. The link is of some use.

However, having spoken to the designer, it's not as critical as I thought and so I've proposed changing the dimensioning scheme to be more like a regular slot and hole and it seems the designer is OK with this.

Apparantly this is a temporary stop gap and isn't worth spending too much time on, there is to be a better mount in the near future which I will spend more time on and will probably look to apply profile of a surface if applicable.

Thanks again.

KENAT, probably the least qualified checker you'll ever meet...

 

[Standing]

Powerhound,
Now that is a good web site. A Star for you.


Bradley
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