True Position of Rectangular Slots

[Ksplice]

Hi,

If I call out the true position of a rectangular slot in only in the x direction, does that apply in the Y direction as well or only in the X direction?

thanks

 

[pmarc]

If you apply only in X direction it can't be applied to Y direction. You need another callout for position in Y direction.

 

[Ksplice]

can I call it out only in the X direction? and then straight dimension the Y locations?

 

[KENAT]

You can do that, in fact with 'notches' in the edge of the part that's often how it's done.

However, if a complete 'slot' I'm wondering why not use position in both directions, and look into the "boundary" concept?

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[KENAT]

Oh, and given your wording, make sure you are applying the FCF correctly - it goes on the size dimension in the 'X' direction to control location in that orientation.

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[KENAT]

Doh, and while I think about it, obviously leave out the dia symbol.

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[Ksplice]

in the X direction the slots are tappered on both walls and in the Y direction only one wall is tappered. So In the Y direction I have a flat surface that a part butts up against, so I want to control the location of that surface and not the entire slot.

 

[Ksplice]

Hey Kenat,

what does FCF stand for?

thanks for all your help by the way

 

[KENAT]

Could I suggest a sketch, as I'm wondering if what I've suggested above is appropriate given the extra info.

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[pmarc]

It would not be in accordance with any GD&T standard I am aware of and I would not encourage to do so. But of course you can try - it would be some kind of combination of geoemetrical tolerancing and coordinate dimensioning. I do not see a benefit of such combination however.

 

[Ksplice]

see attached for an example. is there anything wrong with the way this is done? thanks

 

[powerhound]

That sketch is waaaaay different than I had even imagined. I'm not sure you can use position at all here since there is not a real feature of size to use. Profile of a surface is probably more appropriate.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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SSG, U.S. Army
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[Ksplice]

that would be an iregular feature of size right...so I can't use true position buy I could use surface profile and then add basic dimensions to datum C to control the positions to that datum. would I call out profile in both directions?

 

[fsincox]

I would love to know the function of that?
Frank

 

[dingy2]

It sure looks like a feature of size to me and positional is appropriate.

Dave D.

http://www.qmsi.ca

 

[powerhound]

It doesn't seem to meet the definition of a feature of size. What as I missing Dave?

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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[dingy2]

powerhound:

These are tapered square holes with positional tolerance in one direction only.

Dave D.

http://www.qmsi.ca

 

[pmarc]

And we are dangerously closing to the issue of tapered feature being a feature of size or not...

I am with powerhound on this - tapered features or cones are not features of size so profile tolerance is more appropriate way to go - but that's just my opinion. They indeed have opposite points, but they are not associated with unique single size. How could somebody try to apply bonus tolerance concept to that? Which size should be used for bonus calculation?

I do not want to open this can of worms again. I think we had the discussion enough times before.

 

[MechNorth]

Same old argument about FOS vs non-FOS. No directly opposed sides, not a classical FOS in '94. '09, ok.
Also, no tolerance on the width of the feature. And the location dimension from the edge to the center of the datum-C feature is not basic.
Profile is a far better choice.

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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[KENAT]

So, before the FOS debate goes anywhere, Ksplice what drawing standards (and edition) are you working to?

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