Premium A2 (304) and A4 (316) stainless steel hex bolt. Available in metric coarse threads and select UNC/BSW on request. Mill Test Certificates (MTC), strict dimensional tolerances, and fast dispatch from ready stock.
DIN 931
Stainless Steel Hex Bolt
TRSUTED SS Hex Bolt FOR DEMANDING APPLICATION
Key Specifications
Standards
DIN 931
Grades (Material)
A2 (304), A4 (316)
Strength Classes
A2-70, A4-70 and A4-80
Threads
Metric coarse (default). Fine/UNC/BSW available on request
Sizes
M1.6 to M 70, 3/16" to 2.1/2" (others on request)
Lengths
6-150 mm (others on request)
Head
-
Marking
Grade/class & manufacturer ID as applicable
Certificates
MTC 3.1 / chemical composition & mechanicals available
Compliance
RoHS/REACH; generally non-magnetic in solution-annealed state (slight magnetism possible after cold-work)
Choosing the Right Stainless Steel Hex Bolt
Choosing the Right Hex Bolt
Environment & Corrosion
First choose the material based on where the bolt will be used:
A2 (304) stainless steel
Use for: Indoor, general outdoor, mildly corrosive environments
Typical: machinery, fabrication, frames, structural brackets, plant equipment
A4 (316) stainless steel
Use for: Marine, coastal, chemical, chloride-rich environments
Typical: seafront, jetties, cooling towers, water treatment, food & pharma, chemical plants
Rule:
General indoor/outdoor → A2
Marine / chemical / high-chloride → A4
Match material with the nut and washer:
A2 hex bolt + A2 nut & A2 washers
A4 hex bolt + A4 nut & A4 washers
Joint Type – Full Thread vs Partial Thread
Hex bolts are usually supplied as:
Full thread – DIN 933 / ISO 4017
Threads run almost the full length
Best for clamping joints where the entire joint is under tension
Ideal when a nut is fully engaged and the bolt is not heavily loaded in pure shear across the threaded section
Partial thread (shank) – DIN 931 / ISO 4014
Plain, unthreaded portion under the head
Better for joints with shear/bending where you want a smooth shank in the shear plane
Common in structural or machinery joints where the bolt is both clamped and sheared
Simple guide:
Clamp-only, general use → Full thread (DIN 933 / ISO 4017)
Shear or mixed loading → Partial thread (DIN 931 / ISO 4014)
Strength Class – A2-70 / A4-70 / A4-80
Choose property class based on required clamp load:
A2-70 / A4-70
General purpose structural and machinery joints in stainless steel
Suitable for most fabrication, frames, flanges, and equipment mounting
A4-80
Higher tensile strength stainless
Use where you need higher clamp load in the same diameter or more safety margin in critical joints
Typical for highly loaded, corrosion-exposed joints (flanges, heavy structural brackets, critical assemblies)
Rule:
Standard stainless joints → A2-70 or A4-70
High load / more critical / same diameter but higher strength → A4-80 (with matching nuts)
Thread Form
Metric coarse (default):
Better resistance to galling in stainless
Easier assembly, more forgiving in dirty or slightly damaged threads
Metric fine / UNC / UNF:
Use only when required by:
Existing tapped holes
Imported equipment / OEM drawing
Need for finer adjustment or special thread engagement
Always match diameter + pitch between bolt, nut, and any tapped hole.
Mechanical Properties (Guide)
Mechanical Properties (Guide) – Stainless Hex Bolts
Note: Values below are indicative of standard stainless fastener classes. Exact design should always follow relevant standards and engineering calculations.
A2-70 / A4-70 Hex Bolts
Material: A2 (304) or A4 (316) stainless steel
Property class: 70
Minimum tensile strength ≈ 700 MPa
Typical proof strength ≈ 450 MPa
Use with: A2-70 / A4-70 nuts and washers
Applications:
General stainless structural joints
Machinery, frames, supports, flanges, equipment mounting in appropriate environments
A4-80 Hex Bolts
Material: High-strength A4 (316) stainless
Property class: 80
Minimum tensile strength ≈ 800 MPa
Typical proof strength ≈ 600 MPa
Use with: matching high-strength A4 nuts
Applications:
Higher load, corrosion-exposed joints
Critical assemblies needing more clamp load or safety factor
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Frequently Asked Questions
What is a hex bolt?
A hex bolt is a fastener with a hexagonal head and a threaded shank.
It is used with a nut (and often washers) to clamp parts together in steel, machinery, structures, and equipment.
What is the difference between DIN 933 and DIN 931?
DIN 933 / ISO 4017 → Full thread hex bolt
Threads run almost the entire length.
Best for clamping joints where the bolt works mainly in tension.
DIN 931 / ISO 4014 → Partial thread hex bolt
Has a plain shank under the head and threads only on part of the length.
Better for joints with shear / bending, so the smooth shank sits in the shear plane.
When should I use full thread vs partial thread hex bolts?
Use full thread (DIN 933 / ISO 4017) when:
The joint is mainly clamped in tension
You want maximum adjustment and the nut engages along full length
Use partial thread (DIN 931 / ISO 4014) when:
There is significant shear or bending in the joint
You want a smooth shank passing through the shear plane for better bearing
What do A2-70, A4-70, and A4-80 mean?
These indicate the material and strength class:
A2 / A4 → Stainless steel grade
A2 = 304
A4 = 316
70 / 80 → Property class (strength level)
70 → min tensile ≈ 700 MPa
80 → min tensile ≈ 800 MPa
So:
A2-70 = 304 stainless, 700 MPa class
A4-70 = 316 stainless, 700 MPa class
A4-80 = 316 stainless, 800 MPa high-strength class
Are stainless hex bolts magnetic?
A2/A4 stainless is nominally non-magnetic, but due to cold working, forging and thread rolling, hex bolts often show slight magnetism.
This is normal and does not mean the fastener is not stainless steel
