Composite Profile Tolerance - 2 surfaces
Composite Profile Tolerance - 2 surfaces
(OP)
I have 2 situations that I am unsure about the correct application of a composite profile tolerance.
1. I have two tabs which have cylindrical surfaces to mate to a common cylindrical feature. Both of these tabs are datum A. I want to control each of them with a surface profile of 0.25mm and both of them to each other by the same value.
2. Same part description, but now the two tabs are not datum features. I want to control each of them 0.5 to datum A, and 0.25 to each other.
My understanding of application is:
1. Simply show a single surface profile FCF to 0.25 (no datum reference in the FCF) and put "BOTH AREAS" under the FCF.
2. A composite profile FCF of 0.5 to A, B, C and 0.25 to A, B (assuming) B is the datum in the general direction of the surfaces.
Please let me know if this makes sense.
Thanks,
Jeff
1. I have two tabs which have cylindrical surfaces to mate to a common cylindrical feature. Both of these tabs are datum A. I want to control each of them with a surface profile of 0.25mm and both of them to each other by the same value.
2. Same part description, but now the two tabs are not datum features. I want to control each of them 0.5 to datum A, and 0.25 to each other.
My understanding of application is:
1. Simply show a single surface profile FCF to 0.25 (no datum reference in the FCF) and put "BOTH AREAS" under the FCF.
2. A composite profile FCF of 0.5 to A, B, C and 0.25 to A, B (assuming) B is the datum in the general direction of the surfaces.
Please let me know if this makes sense.
Thanks,
Jeff





RE: Composite Profile Tolerance - 2 surfaces
I think a sketch might help clarify and get you a better answer. I'm trying to work out if your datum order is correct in your option 2, the way you word it sounds like it might be wrong but I'm not sure.
Also, what standard are you working to ASME Y14.5M-94?
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RE: Composite Profile Tolerance - 2 surfaces
Please see attached image for clarification.
We are working to ASME Y14.5M-94.
Thanks,
Jeff
http://f
RE: Composite Profile Tolerance - 2 surfaces
A couple of things about the controls on B. The profile tolerance gives you a 0.5 thick tolerance zone that is oriented to A and simultaneously controls areas B1 and B2. This indirectly controls the coplanarity of B1 and B2 to within 0.5, and the flatness of B1 and B2 individually to within 0.5. So the 0.5 flatness control is redundant. Either the flatness value needs to be tightened to something less than 0.5, or the callout can be removed.
Just to poke my nose in even further, I would question the use of A as a datum feature for B. The A surfaces don't have a lot of height, compared to the distances between the B surfaces (particularly B2) and the A surfaces. Small variations in the shape or tilt of the A surfaces will show up as large apparent deviations in the profile of the B surfaces.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Composite Profile Tolerance - 2 surfaces
I want to (somehow) ensure that datum B maintains its orientation to datum A, which effectively means I want the datum B plane to be perpendicular to the axis of the datum A cylindrical targets (within 0.5). If I just kept the flatness, there would be no control of where B ended up oriented relative to A - in my understanding.
Jeff
RE: Composite Profile Tolerance - 2 surfaces
Everything you said in your last post makes sense. Maybe I wasn't clear in my post - I was recommending that you keep the profile tolerance and get rid of the flatness tolerance.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Composite Profile Tolerance - 2 surfaces
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Composite Profile Tolerance - 2 surfaces
Jeff
RE: Composite Profile Tolerance - 2 surfaces
Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Composite Profile Tolerance - 2 surfaces
Jeff
RE: Composite Profile Tolerance - 2 surfaces
I assume that datum A is 1 plane do both surfaces are on that plane. If one wanted to control the surfaces to each other by, let's say, no more than 0.25mm, then I would show a phantom line (theoretically is an extension line) between both surfaces and then use profile of a surface of 0.25 to become datum A. This is similar to using flatness except flatness is used on one surface only.
Hope this helps.
Dave D.
www.qmsi.ca
RE: Composite Profile Tolerance - 2 surfaces
This still does not address the problem of one of datum B's targets potentially being non-functional. If you look at the attached drawing you see that if you push the part against the radius on the primary datum contact surface and slide it down to contact datum areas B, depending on the part, it will probably only touch one of them. If you move the part off of datum A in order to make them both touch, then A is NOT your primary datum, B is.
Powerhound, GDTP T-0419
Production Manager
Inventor 2009
Mastercam X3
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II
RE: Composite Profile Tolerance - 2 surfaces
If it is the intent to establish an axis from Datum A, then my recommendation would be as follows;
- show a phantom-lined circle, including basic diameter
- indicate on the drawing how you intend to simulate the datum feature(s); e.g. "Engage Datum Targets A1 & A2 against a 50mm cylindrical gage pin" or "Engage Datum Targets A1 & A2 against an expanding mandrel for best fit".
- graphically show the (vertical & horizontal) origins of measurement as being at the center of the phantom circle
- show basic dimensions from the indicated origins of measurement to the datum B targets
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Composite Profile Tolerance - 2 surfaces
Thanks,
Jeff
RE: Composite Profile Tolerance - 2 surfaces
Now, for a more direct approach, you need Y14.5-2009. Sections 8.6.1.2 thru 8.6.1.7. provides good text & graphical explanations of the approach. Basically it indicates the same thought process as for a composite positional control or for multiple single-segment posotion controls, so if you understand composite position tolerancing, it's reasy to grasp the extension to profile controls.
Now, making the bold assumption that your company has not adopted Y14.5-2009, you can still use this new method by invoking / referencing it on the drawing (i.e. under the callout, include a note "PER ASME Y14.5-2009").
Hope that helps.
Jim
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com