CONTEXT OF USE:

In this section, I will explain how to correctly use an unequal profile tolerance with specific examples.

Figure 2

The interpretation of the box in Figure 2 is as follows:

1. Profile tolerance
2. Overall tolerance zone (in this case 0.8)
3. Means an unequal profile tolerance
4. Zone of displacement to the outside of the true profile (in this case 0.2)
5. Datum feature

Figure 3

Figures 3 clearly explain how the symbol can be used compared with the old method.  In the old version of the standard, the only way to highlight unequal profile tolerance was to indicate the tolerance zone with a chain line on the drawing.

The old procedure is allowed under the new standard. You can still use it if you are not comfortable with the new approach. As for me, I have had to work with many drawings that were too heavy in the past… it is always best to lighten the drawings. In my opinion, the new formula seems the best option.

Reference:

ASME Y14.5 – 2009 Standards; New Standards for GD&T, Machine Design Magazine