Using True Position Tolerance In Lieu of Profile? 5

[fishchoke]

My company has a US office and a Japan office. Here in the US we use Y14.5M-1994 and we like to use true position tolerances on holes and profile tolerances on surfaces / flat surfaces. However, our Japan office seems to be doing the opposite, using true position tolerances to control surfaces / flat surfaces and using profile to locate holes. When our Japan prints go to US suppliers many of them are confused by this. I attached a picture showing what we're using here in the US (Method A) and what our Japan guys are doing (Method B). Can anyone tell me which is right, or at least 'more right'? Are they both right? Could Japan be using some kind of JIS GD&T spec that I haven't heard of?

 

[3DDave]

If the Japanese are using something different, it should be referenced on the drawing.

Other than that, it looks like someone there is missing part of the specifications. At the least, profile is a variation relative to a perfect form, but the hole has no perfect form given; the diameter would have to be basic and there would be no size tolerance.

I would be more inclined to think there is a font related problem where the glyphs are in a different order than the characters.

 

[CheckerHater]

I don't have much experience with Japanese companies, but they are supposed to follow ISO standards in some way.

And the way of locating holes in ISO is not much different from ASME.

See here:

http://www.eng-tips.com/viewthread.cfm?qid=420236

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

Here's a general way to look at tolerancing holes:
Position at its heart is a location control, not form.
Profile is at its heart a form control, and often it can control location.

So do you want to use the same symbol to control the form (and size) of a hole, as well as its location? Then go for a profile tolerance.
If you want the form and location to be parsed out to different accuracies, then use the position symbol to tackle location.

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

 

[AndrewTT]

I like position for exactly the reasons Belanger describes. I get individual control over form, size, location, and orientation. The size controls form, but I can refine the form if needed. The position control give me location and orientation, but I can refine the orientation if needed. Profile does everything all at once. Sometimes this is too much and the location gets held tighter than needed because I need tight size or form control. Yes, I can use composite profile or combined controls to break up the tolerances but I find that a lot of people are scared/ignorant/confused of/by these types of FCF.

More to the OP's question, I have used position on features that traditionally would use profile. This was done as an extension of principles, where location was very important and form was not (thanks to Belanger for teaching me this "trick"). However, I would think that you would almost always want to use position for circular holes. I can't think of an advantage to using profile on a circular hole.

 

[fishchoke]

Thanks to all you guys, very helpful.