1. Introduction
DIN 938 is a standard German double-end stud bolt (latest DIN 938:2025), widely used for steel machine tools, hydraulic flanges, pump valves and mechanical assembly. DIN938 Stud Bolt features a fixed 1d tap-in thread length exclusively designed for steel tapped holes. Mixing DIN938 with DIN939 and DIN835 studs is the most common sourcing mistake, causing insufficient thread engagement, thread stripping and flange leakage.
This professional guide is compiled by the TOPBOLT technical team, based on 15 years of DIN fastener manufacturing and overseas engineering experience, covering structure specs, material grades, matching standards, installation rules and failure solutions.
2. DIN938 Structural Features
Standard Specification: DIN 938:2012, size range M3-M68
Core Design: Tap-end thread length bm=1d, optimized for steel base material
Tolerance: Sk6 tight fit for tapping end, 6g standard thread for nut end
2.1 DIN Stud Series Comparison
Standard | Thread Length | Applicable Material | Application |
DIN938 | 1d | Carbon Steel / Alloy Steel | Steel flange & machinery housing |
DIN939 | 1.25d | Cast Iron | Cast iron pump & frame |
DIN835 | 2d | Aluminum Alloy | Lightweight aluminum equipment |
3. DIN938 Material & Grade Selection
Carbon Steel Grades
4.8/5.6: Low-load indoor general fixing 8.8: Standard machinery and flange connection (most popular) 10.9/12.9: Heavy-duty and high-vibration equipment
Stainless Steel Grades
A2-70(304): General outdoor anti-corrosion A4-80(316): Coastal and chemical corrosive environment
Alloy Steel High-temperature Grade
Alloy Steel DIN938 Stud Bolt (A193 B7) is customized for high-temperature pipeline and pressure equipment.
4. Matching Nuts & Washers Standard
Standard assembly: DIN934 hex nut + DIN125 flat washer. DIN127 spring washer for anti-loosening in vibrating conditions. Stainless steel studs must match full stainless accessories to prevent galvanic corrosion. High-temperature alloy studs require professional high-grade matching nuts.
5. Surface Finish Options
Black finish for indoor dry assembly; zinc plating for general outdoor rust resistance; hot-dip galvanizing for outdoor steel structures; PTFE coating for anti-seize and high-temperature working conditions.
6. Standard Installation Guidelines
1. DIN938 is only suitable for steel threaded holes. 2. Clean thread debris before installation to ensure full thread engagement. 3. Tighten evenly in stages to avoid stress concentration. 4. Do not mix different batches or coating types on one project.
7. Common Sourcing Mistakes
1. Wrong stud type for base material causing thread damage. 2. Mismatched carbon and stainless accessories leading to corrosion. 3. Low-grade studs used on heavy-load equipment causing fatigue fracture.
8. Conclusion
DIN938 double-end studs are professional fasteners for steel mechanical assembly. Global buyers must select correct stud type, material grade and matching accessories according to base material and working conditions to ensure long-term structural stability and project qualification.
9. FAQ
Q1: Can DIN938 replace DIN939? A: No. DIN938 is for steel holes while DIN939 is for cast iron. Incorrect replacement causes assembly failure.
Q2: Can stainless studs use carbon steel washers? A: No. Dissimilar metal contact causes galvanic corrosion and thread seizure.
Q3: What grade for high-temperature DIN938 application? A: A193 B7 alloy steel DIN938 studs with dedicated high-temperature nuts are required.
