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
