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Composite Profile of a Surface Is Your Most Powerful Tool (#66A)

(In accordance with Y14.5M-1994 standard)

PDF available for premium site members.

Many of you have requested a Tip or two on composite profile. We decided to use something we are all familiar with — food. Let’s say you run a bakery. Customers have an expectation of how a loaf of bread should “look”. They expect to see a nice radius on the top. They do not want to see the three loaves shown below. The first is just a mess, the second is tall on one end and short on the other and the third has a relatively flat top instead of the radius we have all come to expect. The large profile tolerance controlling the top of the loaf allows all of these undesirable conditions. In the following illustrations the profile tolerance has been revised to be a composite profile tolerance.

Key points about composite feature control frames are 1) the upper segment is just like a single segment tolerance, and 2) the 2nd and lower segments will refine feature to feature location, and for profile tolerances also feature form, and any referenced datum features in the 2nd or lower segments constrain only the rotational degrees of freedom they’re capable of, for the pattern of “Feature relating” tolerance zones.

Here the upper segment controls the location of the top of the loaf to within 10mm. The second segment tightens up the orientation relative to A within 4mm. The third segment controls the shape of the top of the loaf to within 1mm.

Although this Tip was about loaves of bread, we have had many customers with parts that required similar controls. Composite profile of a surface is the only way to clearly define these requirements.

This tip is in accordance with ASME Y14.5M-1994.
This tip was originally released in May 2003.

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Back to Tips Tip added Mar 2024