📏 GD&T Quick Reference
Geometric Dimensioning & Tolerancing symbols per ASME Y14.5. Quick visual reference for the shop floor.
Form Tolerances (No Datum Required)
⏤
Flatness
Surface must lie between two parallel planes. Controls waviness and bow.
⌭
Straightness
Line element or axis must lie within a tolerance zone. Applied to surfaces or axes.
○
Circularity (Roundness)
Each cross-section must lie between two concentric circles.
⌭
Cylindricity
Entire surface must lie between two coaxial cylinders. Combines roundness, straightness, and taper.
Orientation Tolerances (Datum Required)
⊥
Perpendicularity
Feature must be within tolerance zone perpendicular to datum.
∠
Angularity
Feature at a specified angle to datum within tolerance zone.
∥
Parallelism
Feature must be within tolerance zone parallel to datum.
Location Tolerances (Datum Required)
⊕
Position
Most common GD&T callout. Controls location of features (holes, pins, slots) relative to datums. Usually applied at MMC.
◎
Concentricity
Midpoints of all diametrically opposed elements must lie within a cylindrical tolerance zone about the datum axis.
≡
Symmetry
Midpoints of opposed elements must lie within tolerance zone about datum center plane.
Runout Tolerances (Datum Required)
↗
Circular Runout
Controls variation at each circular element independently. Part rotated 360° about datum axis.
↗↗
Total Runout
Controls entire surface simultaneously while rotating about datum axis. More restrictive than circular runout.
Profile Tolerances
⌓
Profile of a Line
Each line element of the surface must lie within a 2D tolerance zone.
⌔
Profile of a Surface
Entire surface must lie within a 3D tolerance zone. Very versatile — can control size, form, orientation, and location.
Material Condition Modifiers
Ⓜ
MMC — Maximum Material Condition
Largest pin, smallest hole. Bonus tolerance available as feature departs from MMC.
Ⓛ
LMC — Least Material Condition
Smallest pin, largest hole. Bonus tolerance as feature departs from LMC.
Ⓢ
RFS — Regardless of Feature Size
Default condition (ASME Y14.5-2009+). Tolerance applies at any produced size.