F4 Wiki

F4 The public, stable reference for GD&T and how the F4 Application interprets it. Each topic pairs standard GD&T guidance with F4 validation behavior so you can move from definition to decision quickly.

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Standard definitions, symbols, and usage guidance.

Rules, checks, and decisions used by the F4 validator.

Short definitions and worked applications.

Browse by category

Straightness, flatness, circularity, cylindricity.	Parallelism, perpendicularity, angularity.
Position, composite, MSS, concentricity, symmetry.	Line, surface, composite, MSS.
Circular and total runout.	Supporting rules and .

Featured pages

GDT:Straightness - basic line element form control.
GDT:Flatness - planar form control.
GDT:Position - primary location control for features of size.
GDT:Profile of a Surface - shape and location combined.
F4:Position Validation - how F4 checks position.

How to use this wiki

The public view shows approved revisions only.
Each GD&T page links to its matching F4 validation page.
Use the sidebar or search to find topics quickly.
When a rule needs interpretation, the F4 page calls out the decision and its impact.

Community

Community forum

Announcements, questions, feature requests, and showcases.

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