The most important control in GD&T is location, location, location - 1994, 2009, 2018 (#25)
(In accordance with the ASME Y14.5-2018 standard)
(In accordance with the ASME Y14.5-2009 standard)
(In accordance with Y14.5M-1994 standard)
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Once datums have been established, other features must be located with respect to the datums. Often those applying GD&T will use orientation and form controls and forget to control the location. Features are located geometrically using profile of a surface, position and, as last month’s Tip explained, sometimes runout. These locating controls automatically provide orientation and, with the exception of position, form control. Form is provided by the size dimension (Rule 1) when using position. Once the features have been located, the orientation and form controls should only be pulled out of the toolbox to be used as refinements. The geometric controls shown in blue come for "free" with the general Profile of a Surface.
This tip is in accordance with ASME Y14.5M-1994, ASME Y14.5-2009 and ASME Y14.5-2018.
This tip was originally released in May 1999.
