Profile of a line (⌒)

How to read it

The symbol is an open arc. The outline it is checked against, the true profile, is defined by basic dimensions or by a digital data file (Cogorno). The National Physical Laboratory’s guide draws the zone as the two lines that envelope circles of the tolerance diameter whose centres lie on the nominal profile, and Keyence describes the same zone on any cross-section parallel to the projection plane. Berez’s notes to ASME Y14.5-2018 give the two profile controls a group of their own that can control location, orientation, size and form, with datum referencing “sometimes”: with no datum the frame controls form only, and with datums it also controls orientation and location. Cogorno notes that datums are generally not used for profile of a line where only the cross-section is being controlled.

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Look-alikes

Profile of a surface ⌓ is the same arc closed by a straight base line, and controls the whole surface rather than single cross-sections. Unicode’s names follow the drafting use: ⌒ (U+2312) ARC, the same character as geometry’s arc sign, is annotated “position of any line” and ⌓ (U+2313) SEGMENT “position of a surface”.