GD&T Reference

1. Form Controls

Form controls apply to individual features and do not require a datum. They define the shape of geometry.

Characteristic	Symbol	Unicode	Of Size?	VC Affected?	Datum Ref?
Straightness	─	U+2014	Yes	Yes	No
Flatness	▭	U+25AD	No	No	No
Circularity	○	U+25CB	No	No	No
Cylindricity	⌭	U+232D	No	No	No

2. Profile Controls

Profile controls can apply to individual or related features and may reference a datum depending on control intent.

Characteristic	Symbol	Unicode	Datum Required?
Profile of a Line	∩	U+2312	Optional
Profile of a Surface	⌒	U+2313	Optional

3. Orientation Controls

These define angular relationships relative to a datum. They always require a datum reference and are affected by size and VC.

Characteristic	Symbol	Unicode	Of Size?	VC Affected?	Datum Ref?
Perpendicularity	⊥	U+27C2	Yes	Yes	Yes
Angularity	∠	U+2220	Yes	Yes	Yes
Parallelism	∥	U+2225	Yes	Yes	Yes

4. Location Controls

Used to locate features relative to a datum. Includes position, symmetry, and concentricity.

Characteristic	Symbol	Unicode	Of Size?	VC Affected?	Datum Ref?
Position	⌖	U+2316	Yes	Yes	Yes
Symmetry	≑	U+2241	Yes	No	Yes
Concentricity	◎	U+25CE	No	No	Yes

5. Runout Controls

Used to control circular or total runout for rotating components. Requires datum reference.

Characteristic	Symbol	Unicode	Datum Ref?
Circular Runout	⌴	U+2334	Yes
Total Runout	⌵	U+2335	Yes

Extra Notes

• VC: Virtual Condition, combines size limit and GD&T tolerance to define assembly limits.
• Bonus Tolerance: Additional tolerance gained with actual feature size reduction (e.g. MMC condition).
• Datum: Reference point, axis, or plane used for GD&T framework.
• Feature of Size: A dimensional feature like a hole or shaft that defines size-related tolerances.