DIN 933, ISO 4017, BS EN ISO 4017: Are They the Same Hex Bolts?

Hex bolt standards like DIN 933, ISO 4017, and BS EN ISO 4017 often show up in international sourcing. They all refer to fully threaded hex head bolts—but are they actually the same?

The short answer: almost—but not quite. Let’s break down the differences and what you should know before choosing the right one for your project.

DIN 933 is a German standard that specifies fully threaded hexagon head bolts with metric coarse threads. It’s one of the most widely used fastener standards in Europe and across global industrial applications.

• Metric thread (coarse pitch)
• Hex head dimensions based on DIN profiles
• Fully threaded along the shank
• Common strength grades: 8.8, 10.9, A2-70, A4-80
• Often hot-dip galvanized, zinc-plated, or stainless steel

DIN 933 bolts are widely used in machinery, metal structures, infrastructure, and OEM manufacturing.

ISO 4017 is the international equivalent of DIN 933—both define fully threaded hex bolts, but ISO is a globalized version with slight dimensional refinements.

The key differences:

• Head height and across-flats width may differ slightly
• Thread tolerances follow ISO guidelines
• ISO 4017 is meant to harmonize fastener dimensions globally

In most cases, DIN 933 and ISO 4017 bolts are interchangeable, especially for non-critical applications.

BS EN ISO 4017 is the British and European adoption of the ISO 4017 standard.

• BS = British Standard
• EN = European Norm
• ISO = International Standard

So, BS EN ISO 4017 bolts are basically ISO 4017 bolts, recognized under the UK and EU framework. You’ll often see this marking in project specifications, tenders, or product catalogs across the UK, Ireland, and Europe.

Standard	Region	Fully Threaded?	Key Use	Interchangeable?
DIN 933	Germany / EU	Yes	Industrial, general engineering	Yes
ISO 4017	International	Yes	Global standard for hex bolts	Yes
BS EN ISO 4017	UK / EU	Yes	Public tenders, spec-driven projects	Yes

Bottom line: For most applications, they can be used interchangeably—just check the spec sheet or call-out in the project documents.

While these standards are functionally equivalent, pay attention to:

• Critical fit dimensions (tight assemblies)
• Approval-sensitive projects (public infrastructure may require exact spec)
• Matched components (pairing with DIN or ISO nuts/washers)

For CE-marked or EN 1090-1 structural steel applications, the BS EN ISO 4017 designation may be explicitly required.

Many fastener manufacturers (like TUHU) can produce bolts that comply with multiple standards, even if only one code is shown on the label. The key is dimension + material + tolerance match.

We supply:

• DIN 933 / ISO 4017 / BS EN ISO 4017 bolts
• In grades 4.8, 8.8, 10.9, A2, A4
• With HDG, zinc-plated, or plain finishes
• Along with MTC, CoC, and CE certification upon request

So—are DIN 933, ISO 4017, and BS EN ISO 4017 the same?

Yes, for most practical purposes. But if you’re working with regulated specs or public tenders, it’s always smart to confirm the exact designation.

Looking for standard-compliant bolts? We’re ready to help.

👉 Contact Us (sales@tuhufasteners.com) to get a quote.