Double End Stud Bolts / Tap End Studs (DIN 938 / DIN 939) – Grade 4.8 / 8.8 – Manufacturer Direct

High-Precision Double End Stud Bolts (DIN 938 & DIN 939) for Machinery and Automotive

At Handan Bolt, we specialize in the manufacturing of high-quality Double End Stud Bolts, often referred to technically as Tap End Studs. Produced in our Yongnian facility, these fasteners are critical components in engine assembly, pump manufacturing, and heavy industrial machinery. Unlike standard fully threaded rods, our DIN 938 and DIN 939 studs feature a precise unthreaded shank in the middle, engineered to specific tolerances.

What is a Double End Stud Bolt?

A Double End Stud is a cylindrical fastener with threads on both ends and a smooth shank in the center. It falls under the broader category of Threaded Rod (Read more on Wikipedia) but is designed for a specific function:

• The “Tap End” (Short End): This end is designed to be screwed permanently into a tapped hole in a component (like an engine block or casting). It is installed until the threads “bottom out” or jam tight.
• The “Nut End” (Long End): This end projects out of the component to accept a nut and washer, securing the mating part (like a cylinder head) in place.

DIN 938 vs. DIN 939: What is the Difference?

We manufacture both standards, and choosing the right one depends on the material you are screwing into. The difference lies in the length of the “Tap End” ($b_1$):

• DIN 938 (1d): The length of the tap end is approximately equal to the diameter of the stud (e.g., for an M10 stud, the tap end is ~10mm). This is typically used when screwing into Steel components.
• DIN 939 (1.25d): The length of the tap end is approximately 1.25 times the diameter (e.g., for an M10 stud, the tap end is ~12.5mm). This provides more thread engagement and is ideal for softer materials like Cast Iron or Aluminum alloy engine blocks.

Material Grades and Strength

Engine and machinery studs endure high stress and vibration. We offer:

1. Grade 8.8 (High Tensile)

This is our most popular grade for automotive and mechanical applications. Made from medium carbon steel (like 45# or 40Cr) and quenched/tempered, these studs provide the high clamp load necessary to prevent gasket leaks in pressurized systems.

2. Grade 4.8 (Mild Steel)

For non-critical applications where high tensile strength is not required, we offer cost-effective Grade 4.8 studs.

Surface Treatments

As shown in your product images, we provide finishes tailored to your needs:

• Black Oxide / Phosphated: The standard finish for Grade 8.8 engine studs. It retains oil (preventing seizing) and offers basic rust protection without affecting thread tolerance.
• Zinc Plated (Blue/White): Provides a bright, corrosion-resistant finish for external machinery parts exposed to the elements.
• Plain (Oiled): For studs that will be welded or further processed.

Common Applications

Our Tap End Studs are widely used in:

• Automotive Engines: Cylinder head studs, exhaust manifold studs.
• Pumps and Valves: Securing flanges and housing covers.
• Heavy Machinery: Mounting motors and gearboxes to base plates.

Why Source from Handan Bolt?

Precision Rolled Threads: Our threads are rolled, not cut, providing superior fatigue strength and smoother engagement.
Interference Fit Options: We can manufacture studs with “Interference Fit” threads on the tap end (sk6 tolerance) to ensure they lock permanently into the casting.
Custom Lengths: While DIN standards specify lengths, we can customize the “Nut End” length ($l$) to suit your specific assembly thickness.

Get a Factory Direct Quote

Are you an automotive parts distributor or an industrial OEM? Source your studs directly from the manufacturer for the best price.

Need a price list for DIN 938/939 studs?

Please click here to Contact Our Sales Team for a Free Quote. We support mixed orders!