Technical Specifications

DIN 940 / GB 900 / UNI 5917 Studs with Extra Long Tap End (≈ 2.5d) 4.8 / 5.8 / 8.8 / 10.9 / 12.9; A2-70/A4-70 Plain, Zinc Plated, Zinc-Nickel, Zinc-Flake (Dacromet), Phosphated
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DIN 940 / GB 900 / UNI 5917 Studs with Extra Long Tap End (≈ 2.5d) 4.8 / 5.8 / 8.8 / 10.9 / 12.9; A2-70/A4-70 Plain, Zinc Plated, Zinc-Nickel, Zinc-Flake (Dacromet), Phosphated
DIN 940 / GB 900 / UNI 5917 Studs with Extra Long Tap End (≈ 2.5d) 4.8 / 5.8 / 8.8 / 10.9 / 12.9; A2-70/A4-70 Plain, Zinc Plated, Zinc-Nickel, Zinc-Flake (Dacromet), Phosphated
DIN 940 / GB 900 / UNI 5917 Studs with Extra Long Tap End (≈ 2.5d) 4.8 / 5.8 / 8.8 / 10.9 / 12.9; A2-70/A4-70 Plain, Zinc Plated, Zinc-Nickel, Zinc-Flake (Dacromet), Phosphated

Standard

DIN 940 / GB 900 / UNI 5917

Specification

M3 - M52

Material

Carbon Steel / Alloy Steel / Stainless Steel (A2, A4, SS431)

Property Class

4.8 / 5.8 / 8.8 / 10.9 / 12.9; A2-70/A4-70

Finish

Plain, Zinc Plated, Zinc-Nickel, Zinc-Flake (Dacromet), Phosphated

Product Description

Designed for deep-hole threading in soft materials (Aluminium/Cast Iron)

Technical Data & Drawings
Model: DIN 940 / GB 900 / UNI 5917 Studs with Extra Long Tap End (≈ 2.5d) pdf
Dimension CodeSpecification (mm)
d
P
L
L (max)
L (min)
b1
ds (max)

Technical Specifications

DIN 940-1995 Studs with Extra Long Tap End (≈ 2.5d)
Product No.
DIN 940
Product Specification
M4 * 20
Product Standard
DIN 940-1995
Material Grade
—
Unit
mm
Mechanical Property
—
Dimension CodeSpecification (mm)Dimension CodeSpecification (mm)
dDiameterM4PPitch0.7
LLength20L(max)Lmax20.42
L(min)Lmin19.58b1b110
ds(max)dsmax4dsRod diameter4
Other Requirements
Technical Conditions
MaterialTypeSteelGeneral Technical Conditions
Grade
ThreadToleranceMechanical PropertyClass
StandardStandard
ToleranceProduct GradeSurface Treatment
Standard
Surface RoughnessSurface Defect
Acceptance & PackingReference Weight per 1000 (kg)

Industrial Applications

1. Powertrain & Engine Manufacturing

  • Typical Application: Engine Block & Cylinder Head Assembly
  • Recommended Specs: M10 * 60 / M12 * 80 | Grade 10.9 | Zinc-Nickel Plated
  • Technical Insight: DIN 940 studs feature an extra-long tap end (≈ 2.5d) specifically designed for aluminum engine blocks. In low-strength base materials, deeper thread engagement effectively distributes axial tension, preventing thread stripping or base material damage during high-torque tightening. The Zinc-Nickel coating provides exceptional thermal and chemical resistance.

2. Fluid Engineering & Heavy Hydraulics

  • Typical Application: Cast Iron Pump Casing Fastening
  • Recommended Specs: M16 * 70 / M24 * 110 | Grade 8.8 | Phosphated & Oiled
  • Technical Insight: In grey or ductile iron pump and valve housings, standard studs are prone to thread fatigue due to constant operational vibration. DIN 940 enhances fatigue strength by increasing the engagement depth. The phosphated and oiled finish ensures a stable torque-to-tension transition during assembly while providing essential rust protection.

3. Railway & Chassis Systems

  • Typical Application: Gearbox Housing Connections
  • Recommended Specs: M12 * 50 / M16 * 80 | Grade 10.9 | Zinc-Flake (Geomet/Dacromet)
  • Technical Insight: Railway equipment faces extreme alternating loads. Grade 10.9 high-tensile DIN 940 studs combined with Zinc-Flake coating offer superior corrosion resistance while completely eliminating the risk of Hydrogen Embrittlement common in high-strength steel, ensuring the absolute safety of chassis components.

4. Light Alloy Structures & Marine Support

  • Typical Application: Magnesium-Aluminum Frame Assembly
  • Recommended Specs: M6 * 30 / M8 * 40 | Stainless Steel A4-80 (SS316) | Passivated
  • Technical Insight: In marine or high-humidity environments, galvanic corrosion is a major risk for light alloy structures. Using A4-80 (SS316) stainless steel DIN 940 studs with strict passivation ensures both load-bearing capacity (via 2.5d engagement) and long-term resistance to pitting and electrochemical corrosion.