This article highlights the key points of GB/T 13914-2002, "Dimensional Tolerances for Stamping Parts," as they apply in real manufacturing. Meeting the tolerance standard matters, but so do feasibility and cost-effectiveness.

The dimensional tolerance of a precision-stamped part is set by both the part size and the tolerance grade you select. Where functional requirements allow it, choosing an economical tolerance grade improves manufacturability.

Dimensional Tolerances of Flat Stamped Parts

Flat stamped parts are divided into 11 grades, ST1 through ST11. ST stands for the dimensional tolerance of flat stamped parts, and the number identifies the grade. Accuracy decreases from ST1 to ST11.

Dimensional Tolerances of Formed Stamped Parts

Formed stamped parts are divided into 10 precision grades, FT1 through FT10. FT stands for the dimensional tolerance of formed stamped parts, and accuracy decreases from FT1 to FT10.

Limit Deviations

For hole dimensions, the lower deviation is generally zero and the upper deviation equals the dimensional tolerance. For shaft dimensions, the upper deviation is generally zero and the lower deviation is the negative dimensional tolerance. Hole-center distance, edge distance, bending, and drawn length and height commonly use equal upper and lower deviations of half the tolerance.

Key Control Points in Production

Bending angle and piercing angle.

1. Pierced fillet radius.
2. Forming dimensions created by bending or drawing.
3. Piercing and blanking dimensions.
4. Material thickness, die clearance, and measurement method.
5. Controlling these items keeps the required precision, meets the design specification, and delivers stable stamped-part quality.

Controlling these items allows manufacturers to maintain the required precision, meet design specifications and achieve stable stamped-part quality.