Collection of Hexagon Small Flange Bolt Cold Heading Processes

11 Typical Forming Schemes for Hex Small Flange Screws

Introduction

Cold heading is the core forming process for hexagon small flange bolts, widely used in automobiles, motorcycles, machinery, and precision assembly. Reasonable station layout directly affects dimensional accuracy, flange flatness, hexagon fullness, and production stability.

This article collects 11 typical cold heading processes specially designed for hexagon small flange bolts, covering 4-station, 3-station, 2-die 3-blow, and single-station double-stroke schemes. It provides complete parameters including equipment, blank size, material, station flow, and deformation ratio, serving as a practical technical reference for manufacturers, mold designers, and process engineers.

1. 4-Station Cold Heading Process

Applicable Equipment: 4-station cold heading machineProcess Flow:

· Station 1: Shank diameter reduction, head upsetting

· Station 2: Secondary head upsetting

· Station 3: Hexagonal and flange forming

· Station 4: Shank end chamfering

Process Feature: Standard cold heading process with stable forming.

2. 2-Die 3-Blow Cold Heading Process

Applicable Equipment: 2-die 3-blow cold heading machine

Blank Spec: d=9.5mm, L=26.7mm

Process Flow:

· Station 1: Shank diameter reduction

· Station 2:  1.Head pre-upsetting

2. Final forming of hex head with recess and small flange

3.  3-Station Cold Heading Process (High-Strength Alloys)

Applicable Equipment: 3-station cold heading machineMaterials:38CrMnNiMo, 20Mn2B, 40CrNiMoA alloy steels, 06CrMnB duplex ferrite-martensitic steel and other low-formability materials.

Process Flow:

· Station 1: Primary diameter reduction

· Station 2: 12-point head forming + secondary shank diameter reduction

· Station 3: Small flange extrusion forming

4. Single-Station Double-Stroke Cold Heading Process

Applicable Equipment: Single-station double-stroke cold heading machineMaterials:20 rimmed steel (σb=420~480MPa), 35 steel (σb≤520MPa)

Process Flow:

· 1st stroke: Shank diameter reduction, end chamfering, tapered head pre-forming

· 2nd stroke: Small flange and hex head upsetting

5. 13BOA-8φ 3-Station Cold Heading Process

Applicable Equipment: 13BOA-8φ 3-station cold heading machineBlank Spec: Diameter 10.3mm, Length 21.2mm

Process Flow:

· Station 1: Forward extrusion reduces diameter from 10.3mm to 6.85mm (reduction ratio: 56%)

· Station 2: Tapered head pre-upsetting + shank end chamfering

· Station 3: Final upsetting of small flanged head; shank upset to 7.15mm with chamfering

6. 13BOA-8 3-Station Cold Heading Process

Applicable Equipment: 13BOA-8 3-station cold heading machineBlank Spec: Diameter 8.1mm, Length 36.8mm

Process Flow:

· Station 1: Diameter reduced from 8.1mm to 6.85mm (reduction ratio: 28%)

· Station 2: Tapered head pre-upsetting + shank end chamfering

· Station 3: Final small flanged head forming; shank upset to 7.15mm with chamfering

7. 4-Station Cold Heading Process (C14 Cr-Mn Steel)

Applicable Equipment: 4-station cold heading machineMaterial: C14 Cr-Mn steel for cold extrusion

Process Flow:

· Station 1: Primary diameter reduction

· Station 2: Shank chamfering + cylindrical head forming

· Station 3: Rough upsetting of hex head, small flange, and secondary diameter reduction

· Station 4: Finishing of small flange and hexagon

8. 4-Station Cold Heading Process (Head First, Shank Later)

Applicable Equipment: 4-station cold heading machine

Process Flow:

· Station 1: Head pre-forming

· Station 2: Hexagonal head forming

· Station 3: Shank diameter reduction

· Station 4: Secondary shank diameter reduction + chamfering

9. 13BOA-8 3-Station Cold Heading Process (Long Shank)

Applicable Equipment: 13BOA-8 3-station cold heading machineBlank Spec: Diameter 9.2mm, Length 56mm

Process Flow:

· Station 1: Primary diameter reduction to 7.75mm (reduction ratio: 29%)

· Station 2: Tapered head pre-upsetting + shank end chamfering

· Station 3: Secondary diameter reduction + final small flanged hex head forming (reduction ratio: 18%)

10. 2-Die 3-Blow Cold Heading Process (General Type)

Applicable Equipment: 2-die 3-blow cold heading machine

Process Flow:

· Station 1: Shank diameter reduction

· Station 2:

1. Head pre-upsetting

2. Head final forming

11. 2-Die 3-Blow Cold Heading Process (Small Precision Parts)

Applicable Equipment: 2-die 3-blow cold heading machineBlank Spec: d=6.22mm, L=22.3mm

Process Flow:

· Station 1: Shank diameter reduction

· Station 2:

1. Head pre-upsetting

2. Head final forming