GD&T defines engineering tolerances through symbolic language on drawings. System describes nominal geometry and permissible variations of physical objects. Allows over 50% more tolerance zone than coordinate dimensioning
Standard applies to aluminum profiles with circumscribing circle up to 800mm. Applies to general engineering applications only. Includes various aluminum alloys from EN AE-1050A to EN AW-6463
Standard specifies tolerances and machining allowances for cast metals and alloys. Applicable to various casting manufacturing processes. Customer should consult foundry before finalizing design
Position symbol controls feature orientation regardless of size. Datum is theoretical reference point for dimensional tolerances. Datum target defines specific point or area for establishing datum
New rule: As-designed dimension value doesn't establish functional or manufacturing target. Concentricity and symmetry tolerances removed from standard. Surface texture and flaws now included in tolerance zone. Radius tolerance changes: arcs become concentric when center located via dimensions
NPT is the most popular series defined in ASME B1-20.1. Threads are designated by diameter in inch fractions and pitch in TPI. Series letters indicate type: N (National), P (Pipe), S (Straight), etc