This article extracts key points from “GB/T13914-2002 Stamping Parts Dimensional Tolerance” in light of practical manufacturing environments. While meeting tolerance standards is essential, feasibility and cost-effectiveness should also be considered.
The size tolerance of precision metal stamping parts is determined by both the size of the part and the selected tolerance level. If the functional requirements are satisfied, selecting an economical tolerance level improves manufacturability.
Dimensional tolerance of flat stamping parts
Flat stamping parts are divided into 11 grades, represented by ST1 to ST11. ST represents the dimensional tolerance of flat stamping parts, and the Arabic numeral identifies the grade. Accuracy decreases sequentially from ST1 to ST11.
Dimensional tolerance of formed stamping parts
Formed stamping parts are divided into 10 precision grades, represented by FT1 to FT10. FT represents the dimensional tolerance of formed stamping parts, and accuracy decreases sequentially from FT1 to FT10.
Limit deviations
For hole dimensions, the lower deviation is generally zero and the upper deviation is the dimensional tolerance. For shaft dimensions, the upper deviation is generally zero and the lower deviation is the negative dimensional tolerance. Hole-centre distance, edge distance, bending, drawing length and height commonly use equal upper and lower deviations of half the tolerance.
Production points to control
- Bending angle and punching angle.
- Punched fillet radius.
- Forming dimensions produced by bending or drawing.
- Punching and blanking dimensions.
- Material thickness, tooling clearance and measurement method.
Controlling these items allows manufacturers to maintain the required precision, meet design specifications and achieve stable stamped-part quality.
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