Cylindricity (⌭)
Cylindricity (⌭) is a form tolerance for a cylinder: every point of its surface has to lie between two coaxial cylinders the tolerance apart. It takes no datum.
Easily confused with
How to read it
The symbol is a circle between two parallel slanted lines. Cogorno’s course guide defines cylindricity as the condition where all points of a cylinder’s surface are the same distance from its axis, and the zone as two coaxial cylinders whose radial distance apart equals the tolerance; the National Physical Laboratory’s guide gives the same zone as two concentric cylinders. Cogorno calls it a composite form tolerance, one that controls Circularity (○), Straightness (⏤) of the surface and taper together. ASME Y14.5-2018 lists it with the form controls, with no datum reference (Berez, UNC Charlotte). Unicode encodes it among its drafting symbols as ⌭ (U+232D) CYLINDRICITY.
Also searched as: ⌭, cylindricity gd&t, cylindricity symbol.
This explains what a symbol specifies on a drawing. It isn't inspection or design guidance; the drawing and the edition of the standard it cites take precedence.
Look-alikes
Circularity ○ checks each cross-section on its own; cylindricity applies to the whole surface. Total runout ⌰ also covers a whole cylindrical surface, but it is read as the part turns about a datum axis, and a runout frame names at least one datum (Cogorno). A cylindricity frame has none.
Read next
- Next in GD&T symbolsProfile of a line (⌒)Profile of a line (⌒) controls the shape of a line on a part, a cross-section through a curved surface, against its exact designed outline. With datums named, it can also control where that outline sits and how it is oriented.
- The same shape in African flagsFlag of EthiopiaEthiopia’s flag is green, yellow and red in equal horizontal stripes with a blue disc in the centre holding a yellow star of equal lines with yellow rays. Ethiopia’s Flag Proclamation makes the green labour, fertility and development, the yellow hope, justice and equality, and the red sacrifice and heroism for freedom and equality; the blue disc is peace and the star the unity of Ethiopia’s nations, nationalities and peoples.
More GD&T symbols
The same shape elsewhere
Browse symbols drawn with circles or lines.
Sources
- Fundamental Good Practice in the Design and Interpretation of Engineering Drawings for Measurement Processes, Measurement Good Practice Guide No. 79, David Flack and Keith Bevan, 2005, National Physical Laboratory (UK), Chapter 4, Form tolerances
- Geometric Dimensioning and Tolerancing for Mechanical Design: Instructors’ Guide, Gene R. Cogorno, guide to the McGraw-Hill textbook, rev. 10/12/2020, Technical Training Consultants, Chapter 5, Form, review answers
- Fundamentals of Geometric Dimensioning and Tolerancing (GD&T), Part I, Jaime Berez, seminar adapted from an undergraduate mechanical engineering course, version 2.1.0, 2023, Center for Precision Metrology, University of North Carolina at Charlotte (Zenodo), Slide 31
- Miscellaneous Technical, Range: 2300–23FF (code chart), The Unicode Standard, Unicode Consortium, Drafting symbols, U+232D
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
Added .