A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is the most common stainless group for indoor and general outdoor fasteners. When hex bolts are specified in this grade, the dimensions remain per ISO 4014 / ISO 4017; the material determines corrosion behavior (good general corrosion resistance) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint). Both are covered below with the size table.
Why Choose A2 Stainless Steel for Hex Bolts
The most common stainless group for indoor and general outdoor fasteners. For hex bolts, this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Good general corrosion resistance |
Galvanic & Galling Considerations
Two important notes for stainless hex bolts: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.
Comparable Grades
For Hex Bolts, the alternative stainless grade is A4 (316). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Hex Bolts Available in A2 Stainless Steel
| Size | Pitch coarse (mm) | Width across flats s (mm) | Width across corners e min (mm) | Head height k nom (mm) | Nominal diameter d (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| M1 | 0.25 | 2.5 | 2.71 | 0.7 | 1.0 | Below the ISO 4017 range (M1.6-M64); manufacturer series | Fully threaded |
| M1.2 | 0.25 | 3.0 | 3.28 | 0.8 | 1.2 | Below the ISO 4017 range (M1.6-M64); manufacturer series | Fully threaded |
| M1.4 | 0.3 | 3.0 | 3.28 | 0.9 | 1.4 | Below the ISO 4017 range (M1.6-M64); manufacturer series | Fully threaded |
| M1.6 | 0.35 | 3.2 | 3.48 | 1.1 | 1.6 | ISO 4014/4017 | Fully threaded |
| M2 | 0.4 | 4.0 | 4.32 | 1.4 | 2.0 | ISO 4014/4017 | Fully threaded |
| M2.5 | 0.45 | 5.0 | 5.45 | 1.7 | 2.5 | ISO 4014/4017 | Fully threaded |
| M3 | 0.5 | 5.5 | 6.01 | 2.0 | 3.0 | ISO 4014/4017 | Fully threaded |
| M4 | 0.7 | 7.0 | 7.66 | 2.8 | 4.0 | ISO 4014/4017 | Fully threaded |
| M5 | 0.8 | 8.0 | 8.79 | 3.5 | 5.0 | ISO 4014/4017 | Fully threaded |
| M6 | 1.0 | 10.0 | 11.05 | 4.0 | 6.0 | ISO 4014/4017 | Fully threaded |
| M8 | 1.25 | 13.0 | 14.38 | 5.3 | 8.0 | ISO 4014/4017 | Fully threaded |
| M10 | 1.5 | 16.0 | 17.77 | 6.4 | 10.0 | ISO 4014/4017 | Fully threaded |
| M12 | 1.75 | 18.0 | 20.03 | 7.5 | 12.0 | ISO 4014/4017 | Partial / fully threaded |
| M14 | 2.0 | 21.0 | 23.36 | 8.8 | 14.0 | ISO 4014/4017 | Partial / fully threaded |
| M16 | 2.0 | 24.0 | 26.75 | 10.0 | 16.0 | ISO 4014/4017 | Partial / fully threaded |
| M18 | 2.5 | 27.0 | 30.14 | 11.5 | 18.0 | ISO 4014/4017 | Partial / fully threaded |
| M20 | 2.5 | 30.0 | 33.53 | 12.5 | 20.0 | ISO 4014/4017 | Partial / fully threaded |
| M22 | 2.5 | 34.0 | 37.29 | 14.0 | 22.0 | ISO 4014/4017 | Partial / fully threaded |
| M24 | 3.0 | 36.0 | 39.98 | 15.0 | 24.0 | ISO 4014/4017 | Partial / fully threaded |
| M27 | 3.0 | 41.0 | 45.2 | 17.0 | 27.0 | ISO 4014/4017 | Partial / fully threaded |
| M30 | 3.5 | 46.0 | 50.85 | 18.7 | 30.0 | ISO 4014/4017 | Partial / fully threaded |
| M33 | 3.5 | 50.0 | 55.37 | 21.0 | 33.0 | ISO 4014/4017 | Partial / fully threaded |
| M36 | 4.0 | 55.0 | 60.79 | 22.5 | 36.0 | ISO 4014/4017 | Partial / fully threaded |
| M39 | 4.0 | 60.0 | 66.44 | 25.0 | 39.0 | ISO 4014/4017 | Partial / fully threaded |
| M42 | 4.5 | 65.0 | 71.3 | 26.0 | 42.0 | ISO 4014/4017 | Partial / fully threaded |
| M45 | 4.5 | 70.0 | 76.95 | 28.0 | 45.0 | ISO 4014/4017 | Partial / fully threaded |
| M48 | 5.0 | 75.0 | 82.6 | 30.0 | 48.0 | ISO 4014/4017 | Partial / fully threaded |
| M52 | 5.0 | 80.0 | 88.25 | 33.0 | 52.0 | ISO 4014/4017 | Partial / fully threaded |
| M56 | 5.5 | 85.0 | 93.56 | 35.0 | 56.0 | ISO 4014 | Partial / fully threaded |
| M60 | 5.5 | 90.0 | 99.21 | 38.0 | 60.0 | ISO 4014 | Partial / fully threaded |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this bolt in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
