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HV Structural Bolt Dimensions (DIN 6914, M12 to M36)
Guide · Updated October 28, 2026
DIN 6914 covers class 10.9 HV structural hex bolts with large width across flats, M12 to M36, now superseded by EN 14399-4. Width across flats, width across corners, head height and short-bolt thread length agree across the Wegertseder DIN 6914 sheet, the Sparkfix DIN 6914 spec and the HBS Solutions datasheet (M36 thread length from Sparkfix and HBS). Skipped: long-bolt thread length and tolerances. Check your supplier for critical work.
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Step by step
- Pick the bolt size: Choose M12 to M36. DIN 6914 bolts are class 10.9 for preloaded steel joints.
- Pick the wrench: Width across flats s is larger than a normal hex bolt, e.g. 32 mm at M20 instead of 30.
- Check head height: Head height k is the nominal value.
- Check thread length: Thread length b shown is for shorter bolts; longer bolts get a longer b.
- Build the set: Use DIN 6915 nuts and DIN 6916 washers from the same HV set.
- Size the length: Grip plus washers plus nut plus a few thread pitches of projection.
DIN 6914 HV bolt dimensions (mm)
Columns: thread, width across flats s, width across corners e min, head height k, thread length b (shorter bolts).
- Thread | s | e min | k | b
- M12 | 22 | 23.91 | 8 | 21
- M16 | 27 | 29.56 | 10 | 26
- M20 | 32 | 35.03 | 13 | 31
- M22 | 36 | 39.55 | 14 | 32
- M24 | 41 | 45.2 | 15 | 34
- M27 | 46 | 50.85 | 17 | 37
- M30 | 50 | 55.37 | 19 | 40
- M36 | 60 | 66.44 | 23 | 48
Worked example: M20 HV bolt
An M20 DIN 6914 bolt takes a 32 mm wrench, has a 13 mm head and about 31 mm of thread on shorter lengths. Pair it with a DIN 6915 nut and a 4 mm DIN 6916 washer.
Common problems
- Wrench does not fit: HV heads are one size larger than ISO 4014 hex bolts.
- Lost preload: mixing non-HV nuts or washers into the set.
- Thread in the shear plane: check b against the grip.
FAQ
What is DIN 6914?
A class 10.9 hex bolt with large width across flats for high-strength preloaded (HV) steel structure joints, used with DIN 6915 nuts and DIN 6916 washers.
What is the EN or ISO equivalent?
EN 14399-4 (HV system) replaced DIN 6914. One supplier also cross-references ISO 7411; another says DIN 6914 has no exact equivalent. Check EN 14399-4 for new work.
Why is the head bigger than a normal hex bolt?
The larger bearing area spreads the high preload. M20 uses a 32 mm wrench, M24 a 41 mm wrench.
What was skipped?
The longer thread length for long bolts (sources disagree at M24: 36 vs 37 mm), plus tolerances, shank and bearing face sizes that only one source lists.
Can I use regular washers?
No. Use hardened DIN 6916 / ISO 7416 HV washers.
Related guides and calculators
- HV structural nuts (DIN 6915)
- HV structural washer dimensions (DIN 6916 / ISO 7416)
- Heavy-duty washer dimensions (DIN 7989)
- Square taper washer dimensions (DIN 434 / 435)
- Flat washer size chart (SAE, USS, metric)
- All free machinist calculators
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General shop information only — follow your drawing, tool maker's data and your quality system.