DIN 933

Product grades A and B

This International Standard specifies the characteristics of hexagon head screws with threads from M1.6 up to and Including M64, of product grade A for threads M1.6 to M24 and nominal lengths up to and including 10 d or 150 mm, Whichever is shorter, and product grade B for threads over M24 or nominal lengths over 10 d or 150 mm, whichever is shorter.

Commercially, the steel quality used to manufacture of the ISO 933 grade 8.8 bolts includes Grades A2 and A4 class 70 . The tensile strength for both these steel grades is around 700 Mpa. The strength of the ISO933 bolt M10x18 is indicated by the marking on the head and it is also defined by the applicable product standard. The A2 version of theISO933 bolt material is manufactured from Stainless Steel grade 304, which is known for its Corrosion Resistant properties.

This can be attributed to the high content of chromium and nickel in the alloy of the ISO 933 bolt M8x15 (Metallurgically, the A2 or the ASTM-304 has a designation of 18/8 Stainless Steel or 18% Chromium & 8% Nickel). Although the A2 is mostly considered to be a non-magnetic austenitic stainless steel grade, some residual magnetism of the alloy can be introduced when the material of the IS O933 Bolts are cold worked.

Similar to the A2, the A4-70 ISO 933 bolt material specification is an austenitic, acid proof stainless grade. Usually, the A4-70 is manufactured from stainless steel grade 316 material or its low carbon variant grade 316L. stainless steel grade 316 has been cold worked to provide a minimum tensile ISO933 bolt strength of 700 MPa.

As compared to stainless steel grade 304, grade 316 provides better overall corrosion resistant properties. This holds true particularly as grade 316 stainless steel has a higher resistance to both pitting as well as crevice corrosion in chloride environments. The good corrosion properties of the ISO933 hex bolt manufactured from Grade 316 stainless steel can be attributed to the high molybdenum content in its alloy.

Specifications and reference International Standards
Material Steel Stainless Steel Non-ferrous metal
General Requirement International
ISO 8992
Thread Tolerance Class 6g
International Standard ISO 724, ISO 965-1
Mechanical properties Property classa d < 3 mm: as agreed 3 mm ≤ d ≤ 39 mm:
5.6, 8.8, 9.8, 10.9 d > 39 mm: as agreed
d ≤ 24 mm:
A2-70, A4-70
24 mm < d ≤ 39 mm:
A2-50, A4-50
d > 39 mm: as agreed
Materials are specified in ISO 8839.
3 mm ≤ d ≤ 39 mm: ISO 898-1
d < 3 mm and d> 39 mm: as agreed
d ≤ 39 mm: ISO 3506-1
d > 39 mm: as agreed
Tolerances Product grade For d≤ 24 mm and l ≤ 10d or 150 mmb: A
For d> 24 mm or l > 10d or 150 mmb: B
Standard ISO 4759-1
Tolerances Product Grade For d≤ 24 mm and l ≤ 10d or 150 mmb: A
For d> 24 mm or l > 10d or 150 mmb: B
DIN 267 Part 2 shall apply with regard to surface roughness.
DIN 267 Part 19 shall apply with regards to permissible surface discontinuities.
DIN 267 Part 9 shall apply with regards to electroplating.
DIN 267 Part 10 shall apply with regards to HDG.
Finish - Coating As processed Plain Plain
Requirements for electroplating are specified in ISO 4042. Requirements for electroplating are specified in ISO 4042.
Requirements for non-electrolytically applied zinc flake coatings are specified in ISO 10683.
Additional requirements or other finishes or coatings shall be agreed between the supplier and the purchaser
Acceptability   Acceptance inspection is specified in ISO 3269.
a)  Other property classes are specified in ISO 898-1 for steel and ISO 3506-1 for stainless steel, respectively.
b)  Whichever is the shorter.
Marking of Bolts

Hexagon head bolts according to this document shall be marked with ISO 898-1.
a) Property class marking in accordance with EN ISO 898-1.

Example 1 8.8

b) Identification mark of the RFL.
It is permissible for the marking to be either embossed or indented on the top surface of the head.

Example 2 bolt making


Example - A hexagon head bolt with thread M16, nominal length l = 100 mm and property class 8.8 is designated As follows:
Hexagon head bolt DIN 933 - M16× 100 - 8.8 .