Metric thread

Here is a concise summary of the provided text about metric threads:

Metric Thread (ISO profile) – cylindrical type, most common for nuts and bolts. Standardized in 1946 based on the metric system.

• 60° thread angle (like NPT), but edges are more rounded (like BSP).

• Designation: Letter M + diameter in mm × pitch.
  Example: M8×1 = 8 mm diameter, 1 mm pitch.

• Standards: ISO 68-1 and ISO 965-1.

• Sealing: Not pressure-tight; needs sealant (joint or metal-metal contact).

Two types:

1. Thin (fine) pitch – more threads per axial distance, less thread length. Used for limited screwing space (e.g., thin walls). Example: M8×1.

2. Thick (coarse) pitch – fewer threads per axial distance, more thread length. Example: M8×1.25.

Comparison:

• Mainly used in Europe.

• US equivalents (inch-based): UNC (coarse) and UNF (fine). Example equivalent: M8×1 ≈ 5/16″-18 UNC or 5/16″-24 UNF.

Note: BADA manufactures BSP threads (ISO228) but can produce metric threads on request.