The Design Group at my current company is using GD&T in the block tolerance. Not the normal plus minus tolerance but a statement that all dimensions are basic and uses a profile tolerance for all dimension tolerances. I have never seen this in past companies. Is this a generally accepted practice?
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GD&T in the tolerance block
- Thread starter dpwalker
- Start date
pmarc
Mechanical
- Sep 2, 2008
- 3,248
Yes, it is. Look at this link just as an example:
- Thread starter
- #3
Thanks. Your reference says it should only be applied to surfaces by putting it in the block tolerance it is applying to all dimentions there are no othere tolerances in the block so it applies to everything and therefore is incorrectly applied -- correct?
There should be a "Unless Otherwise Specified" statement before the general surface profile. It would otherwise conflict with a feature of size (FOS) as defined by directly opposed points, and a toleranced size dimension. Everything without a specific / directly applied control falls under the general surface profile. Anything that is not a FOS is a surface.
Perhaps you should post an image of the title block so that we can see exactly what you are dealing with.
It's perfectly legal to use a general surface profile. As for how common it is, it is growing in popularity as it provides a full and complete product definition. As we move toward cad-model based manufacturing and metrology, you will see it even more.
Jim Sykes, P.Eng, GDTP-S
Profile Services TecEase, Inc.
Perhaps you should post an image of the title block so that we can see exactly what you are dealing with.
It's perfectly legal to use a general surface profile. As for how common it is, it is growing in popularity as it provides a full and complete product definition. As we move toward cad-model based manufacturing and metrology, you will see it even more.
Jim Sykes, P.Eng, GDTP-S
Profile Services TecEase, Inc.
- Thread starter
- #6
Looks OK to me -- except that you should lose the comma after the 14.5.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
The example might be applicable to the tec ease situation shown above which is relatively simple part but would the datum structure be relevant on complex parts. The primarily datum is usually the mounting face with the secondary usually a hole and the tertiary datum is usually another hole. All dimensions would come from the primary and secondary datum. One usually develops the datum structure from the part function. Would this datum structure be relevant in all surfaces? mmmmm
Of course, if the datum structure is developed from the bottom surface and two sides (not really from the part function) it might be valid.
I remember one company that was forced by the automotive customer to place a default profile of a surface tolerance of 0.5 mm but I also noted the same tolerance in a FCF on one surface. When I asked why they separated one profile of a surface with the same tolerance on the particular surface, I was told that all the other default surfaces were meaningless but this particular surface had importance to the parts "function and relationship" and they wanted the shop floor to be aware of it. This was a high volume die cast shop so they would end up placing ongoing quality control on the one surface that had functional importance.
Just some thoughts from a different perspective.
Dave D.
Of course, if the datum structure is developed from the bottom surface and two sides (not really from the part function) it might be valid.
I remember one company that was forced by the automotive customer to place a default profile of a surface tolerance of 0.5 mm but I also noted the same tolerance in a FCF on one surface. When I asked why they separated one profile of a surface with the same tolerance on the particular surface, I was told that all the other default surfaces were meaningless but this particular surface had importance to the parts "function and relationship" and they wanted the shop floor to be aware of it. This was a high volume die cast shop so they would end up placing ongoing quality control on the one surface that had functional importance.
Just some thoughts from a different perspective.
Dave D.
Unless they are working to the 1994 standard. (And if 2009, there is no M.)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
There is no "M" in the '09 callout; it is just Y14.5-2009.
Jim Sykes, P.Eng, GDTP-S
Profile Services TecEase, Inc.
Jim Sykes, P.Eng, GDTP-S
Profile Services TecEase, Inc.
Yes, using a common Profile tol frame in the title block is growing in popularity. I implemented it in the title block of my last company. I would recommend using the "ALL OVER" modification instead of "applies to all surfaces", since that is clearly defined in ASME Y14.5-2009.
Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion
Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion
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