GD&T symbols on drawings
The 14 symbols you find in a feature control frame: what each means, whether it needs a datum, and how it relates to lathe work.
Quick answer
The 14 ISO 1101 symbols in 4 groups: form (straightness, flatness, circularity, cylindricity) — no datum; orientation, location and runout — to a datum; line and surface profile — with or without one. On a lathe part you mostly meet runout and circularity.
Straightness
Прямолинейность · form · datum: no
shaft generatrix: deflection of a long part, worn ways
Flatness
Плоскостность · form · datum: no
faced end: dish or crown from tool wear
Circularity (roundness)
Круглость · form · datum: no
out-of-round from clamping a thin-wall part in a 3-jaw chuck
Cylindricity
Цилиндричность · form · datum: no
roundness + straightness + taper together: a long shaft without the tailstock tapers
Profile of a line
Форма заданного профиля · profile · datum: optional
contour of a sphere, radius, form surface
Profile of a surface
Форма заданной поверхности · profile · datum: optional
whole form surfaces
Parallelism
Параллельность · orientation · datum: yes
two faces of a part: facing after re-chucking
Perpendicularity
Перпендикулярность · orientation · datum: yes
face to axis: face in the same setup as the diameter
Angularity
Наклон · orientation · datum: yes
taper or chamfer at an angle to the axis
Position
Позиционный · location · datum: yes
holes on a flange — mostly drilling and milling work
Coaxiality / concentricity
Соосность (концентричность) · location · datum: yes
diameters on one axis: turn in one setup or between centers
Symmetry
Симметричность · location · datum: yes
keyway relative to the axis — a milling job
Circular run-out
Радиальное / торцовое биение · run-out · datum: yes
dial indicator while rotating the part: the most common tolerance on turned parts
Total run-out
Полное биение · run-out · datum: yes
indicator over the whole surface while rotating and traversing
Reading a feature control frame
Symbol on the left (here circular run-out), the tolerance in mm in the middle, the datum letter on the right. It reads: "run-out of this surface relative to datum A must not exceed 0.02 mm". A Ø before the value means a cylindrical tolerance zone, as with coaxiality. A datum is shown on the drawing as a letter in a box with a filled triangle.
The lathe rule of thumb: anything tied together by run-out, coaxiality or perpendicularity is best machined in one setup. Every re-chucking adds the chuck's own run-out (typically a few hundredths of a millimeter).
GOST 2.308 has two more symbols not in ISO: longitudinal section profile and axis intersection. US ASME Y14.5-2018 removed concentricity and symmetry — position, run-out or profile are used instead.
The 14 characteristics, groups and datum requirement follow ISO 1101:1983 (official text: IS 8000-1:1985, identical, open at law.resource.org); the current ISO 1101:2017 uses the same symbols. Russian names follow GOST 2.308. Symbols are simplified for the screen; lathe notes are typical practice.