Typical Processing Routes

1. Small-Specification Bolts Below Class 8.8 (M16 and Below)

• Raw Material Selection: Low-carbon steel

• Blank Forming Method: Cold heading

• Thread Forming: Thread rolling or thread chasing (criteria for selecting thread rolling or thread chasing)

Processing Route:

Raw material (material selection)
→ Material modification → Cold heading → Machining (chamfering, end facing) → Thread rolling or thread chasing → Surface treatment (as required) → Final inspection → Packaging

2. Large-Specification Bolts of Class 12.9 (M16 and Above)

• Raw Material Selection: Medium-carbon alloy steel (35CrMo, 42CrMo, SCM435, etc.)

• Blank Forming Method: Hot heading

• Thread Forming: Thread rolling

Processing Route:

Raw material (material selection)
→ Material modification → Cutting → Machining (turning of thread blank) → Hot heading → Machining (turning of head, chamfering, end facing, overall length sizing, etc.)
→ (Marking) → (Shot blasting)
→ Grinding (grinding of thread blank) → Thread rolling → Dephosphatizing → Heat treatment → Flaw detection → Surface treatment → Final inspection → Packaging

3. Nut Processing Route

Nuts Formed by Hot Heading (Large Specifications)

• Material Selection (according to nut property requirements)

Processing Route:

Material modification → Cutting → Hot heading → Machining (mainly for machining thread bottom hole, end facing to ensure height)
→ (Marking) → Tapping → (Heat treatment) → Surface treatment → Final inspection → Packaging

Alternatively:

Material modification → Cutting → Hot heading → Machining (mainly for machining thread bottom hole, end facing to ensure height)
→ (Marking) → (Heat treatment) → Tapping → Surface treatment → Final inspection → Packaging

Whether heat treatment is required for the nut shall be determined according to the required mechanical properties of the nut.