Cutting dies tolerances classes
Metric ISO thread acc. DIN 13 - coarse and fine thread
4h = tolerance class "fine"
6h = tolerance class "middle", for small diameters (up to M 1.4)
6g = tolerance class "middle" - standard
6e = undersize tolerance; for bolts that receive a surface threatment or a galvanizing (layer thickness up to 8 µm). Cutting dies with 6e tolerance are cutting about 0,03 mm smaller than normal cutting dies with 6g tolerance.
8e = Untermaß-Toleranz; für Bolzen, die eine starke Beschichtung erhalten (Schichtstärke ca. 16 - 18 µm)
Unified thread UNC, UNF, UNEF, UNS, UN, UNJC, UNJF, etc.
3A = tolerance "fine"
2A = standard tolerance "middle"
1A = tolerance "coarse"
Whitworth pipe thread G (BSP) acc. to DIN-ISO 228
A = Standard tolerance "middle"
B = Tolerance "coarse"
Preparation of workpiece:
- concentrical chamfer - ease entry of cutting
- workpiece diameter must be less than the nominal diameter
- Standard chamfer (length, see at the item)
- Spiral entry: free flow of chips ahead of the die and a reducing of cutting torque. This resulsts in an improved surface finish on the cut threads and longer die life
- 70° (short chamfer) - chamfer length: 1,25 pitch = 70°