Hex Flange Bolt

DIN 6921  ·  Grade 8.8 & 10.9 High Tensile  ·  Stainless Steel A2  ·  M6 to M20

The hex flange bolt to DIN 6921 is a hexagon head bolt with an integrated circular flange below the head that acts as a built-in bearing washer. The flange distributes clamping load over a significantly larger area than a standard hex bolt — eliminating the need for a separate washer, resisting pull-through in oversized holes and providing exceptional vibration resistance when serrated. Excel Trading Corporation stocks in Grade 8.8, Grade 10.9 high tensile and Stainless Steel A2 (SS304).

DIN 6921 — Specifications

Standard

DIN 6921 / DIN EN 1665

Thread

M6 to M20 · Coarse pitch · 6g tolerance

Grades Available

8.8 · 10.9 · Stainless A2 (SS304)

Finish

Zinc Plated · Plain · Passivated (SS)

Flange Type

Plain & Serrated (specify on enquiry)

Hex Flange Bolt DIN 6921 Grade 8.8 10.9 Stainless Steel

Available In

8.8

Grade 8.8

High Tensile

10.9

Grade 10.9

High Tensile

SS

Stainless Steel A2

SS304

Available Sizes — DIN 6921

Key dimensions to DIN 6921. The flange diameter (dc) is the critical dimension — it is significantly larger than the hex across-flats (s), creating the wide bearing surface. All sizes available in Grade 8.8, 10.9 and Stainless A2 in standard lengths. Contact us for non-standard lengths.

Thread (d) Pitch (mm) Hex A/F — s (mm) Flange Ø — dc (mm) Head Height — k (mm) Common Lengths (mm)
M6 1.0 10 14.2 7.3 10 · 12 · 16 · 20 · 25 · 30 · 35 · 40
M8 1.25 13 17.9 9.4 12 · 16 · 20 · 25 · 30 · 35 · 40 · 50 · 60
M10 1.5 15 21.8 11.4 20 · 25 · 30 · 35 · 40 · 50 · 60 · 70 · 80
M12 1.75 18 26.0 13.8 25 · 30 · 35 · 40 · 50 · 60 · 70 · 80
M14 2.0 21 29.9 15.9 30 · 40 · 50 · 60 · 70 · 80
M16 2.0 24 34.5 18.3 35 · 40 · 50 · 60 · 70 · 80 · 100
M20 2.5 30 42.8 22.4 40 · 50 · 60 · 70 · 80 · 100 · 120

Which Grade Do You Need?

Click your application to see the recommended grade.

Grade Options

8.8

Grade 8.8

800 MPa · Standard High Tensile

Medium carbon steel, quenched and tempered. The standard high tensile grade for structural and industrial applications. Proof load 640 MPa. Available zinc plated (white or yellow) or plain. Compatible with Grade 8 flange nuts.

General fabrication · Automotive body · EV battery modules · Machinery · Switchboards

10.9

Grade 10.9

1000 MPa · Extra High Tensile

Alloy steel, quenched and tempered to higher strength. Proof load 900 MPa. For critical high-preload joints — engine mounts, suspension, battery pack structural frames, heavy equipment. Must be paired with Grade 10 flange nuts. Requires controlled tightening torque.

Automotive chassis · Engine mounts · EV battery frames · Heavy machinery · Suspension

SS

Stainless A2 / SS304

ISO 3506 · A2-70 · Passivated

304-grade austenitic stainless steel, A2-70. Fully corrosion resistant. Lower tensile than high tensile grades but far superior durability in outdoor, coastal and humid environments. SS316 (A4) available on request. Non-magnetic.

Outdoor enclosures · Coastal construction · Solar mounting · Food equipment · Marine

Quick Specifications

M6–M20

Thread Range

DIN 6921

Standard

3 Grades

8.8 · 10.9 · SS A2

6g

Thread Tolerance

Installation Notes

  • ▸ The flange must seat fully flat against the mating surface — if the hole is countersunk or chamfered, the flange will rock and preload will be uneven.
  • ▸ Serrated flange bolts should not be used on soft materials like aluminium or plastics — the serrations will gouge the surface. Use plain flange bolts and add a lock washer if needed.
  • ▸ Grade 10.9 bolts require a torque wrench — never tighten to feel. Refer to the standard torque table for each diameter and lubrication condition.
  • ▸ In EV battery pack applications, always follow the OEM torque specification — consistent and repeatable preload directly affects cell compression uniformity and thermal performance.

Frequently Asked Questions

What is a hex flange bolt and why use it instead of a standard hex bolt with a washer?

A hex flange bolt has a wide circular flange integrated below the head — equivalent to a fixed washer. The flange covers a larger bearing area than a standard washer, distributes clamping load more evenly and cannot spin or fall out during assembly. In high-volume production — automotive, EV battery, switchboard — it eliminates loose washer handling entirely, reducing assembly time and preventing washer misalignment errors.

What is the difference between Grade 8.8 and Grade 10.9?

Grade 8.8 has 800 MPa minimum tensile strength and 640 MPa proof load — the standard choice for the majority of industrial and automotive applications. Grade 10.9 has 1000 MPa tensile and 900 MPa proof load — for critical, high-preload joints. Grade 10.9 must only be paired with Grade 10 nuts and must be tightened to a specified torque. For battery module assembly, Grade 8.8 is typical for internal connections; Grade 10.9 is used in structural pack frames.

Are hex flange bolts used in lithium-ion battery packs?

Yes — hex flange bolts are a standard fastener in EV lithium-ion battery module and pack assembly. The integrated flange provides uniform, consistent clamping pressure across battery cell compression plates and module holders without the washer variability that affects torque consistency. Grade 8.8 zinc plated is standard for internal module assembly. Grade 10.9 is used in structural battery pack frames. Stainless A2 is used for external pack mounting where underbody moisture exposure is a factor.

What is the difference between serrated and plain flange bolts?

Serrated flange bolts have teeth on the underside of the flange that bite into the mating surface on tightening, providing locking action without a separate lock washer — essential for vibration-heavy applications like automotive and machinery. Plain (smooth) flange bolts are used where the mating surface must not be marked — painted surfaces, aluminium panels, precision components. Both variants are stocked — specify on enquiry.

Where can I buy DIN 6921 hex flange bolts in Bangalore?

Excel Trading Corporation stocks DIN 6921 hex flange bolts in Grade 8.8, Grade 10.9 and Stainless Steel A2 at our Kumbarpet store in Bengaluru. We supply to automotive OEMs, EV battery manufacturers, construction companies and general fabricators across Karnataka and India-wide. Call +91-9448239476 or email info@exceltrading.in for sizes, pricing and bulk availability.