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 knurled thumb screws, low type are specified in this grade, the dimensions remain per DIN 653; 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 Knurled Thumb Screws, Low Type
The most common stainless group for indoor and general outdoor fasteners. For knurled thumb screws, low type, 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 knurled thumb screws, low type: (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 Knurled Thumb Screws, Low Type, 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
The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.
Sizes of Knurled Thumb Screws, Low Type Available in A2 Stainless Steel
| Size | a_max (mm) | c (mm) | Head diameter dk (mm) | dk_max (mm) | dk_min (mm) | ds_nom_max (mm) | ds_min (mm) | e (mm) | Head height k (mm) | k_min (mm) | r (mm) | Knurling | Length range l (mm) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M1 | 0.75 | 5.5 | 5.74 | 5.26 | 1.5 | 1.25 | 0.5 | 0.5 | 2~6 | DIN 653 | ||||
| M1.2 | 0.75 | 6 | 6.24 | 5.76 | 1.5 | 1.25 | 0.5 | 0.5 | 2~8 | DIN 653 | ||||
| M1.4 | 0.9 | 7 | 7.29 | 6.71 | 2 | 1.75 | 0.5 | 0.5 | 3~10 | DIN 653 | ||||
| M1.6 | 1.05 | 7.5 | 7.79 | 7.21 | 2 | 1.75 | 0.5 | 0.5 | 3~12 | DIN 653 | ||||
| M2 | 1.2 | 9 | 9.29 | 8.71 | 2 | 1.86 | 1.5 | 2 | 1.75 | 0.5 | 0.5 | 4~16 | DIN 653 | |
| M2.5 | 1.35 | 0.3 | 11 | 11.35 | 10.65 | 2.5 | 2.36 | 2 | 2.5 | 2.25 | 0.5 | 0.6 | 5~18 | DIN 653 |
| M3 | 1.5 | 0.3 | 12 | 12.35 | 11.65 | 3 | 2.86 | 2 | 2.5 | 2.25 | 0.5 | 0.6 | 6~20 | DIN 653 |
| M4 | 2.1 | 0.4 | 16 | 16.35 | 15.65 | 4 | 3.82 | 3 | 3.5 | 3.2 | 0.5 | 0.6 | 8~25 | DIN 653 |
| M5 | 2.4 | 0.4 | 20 | 20.42 | 19.58 | 5 | 4.82 | 3 | 4 | 3.7 | 1 | 0.6 | 10~30 | DIN 653 |
| M6 | 3 | 0.5 | 24 | 24.42 | 23.58 | 6 | 5.82 | 4 | 5 | 4.7 | 1 | 0.6 | 12~30 | DIN 653 |
| M8 | 3.75 | 0.6 | 30 | 30.42 | 29.58 | 8 | 7.78 | 5 | 6 | 5.7 | 2 | 0.6 | 16~35 | DIN 653 |
| M10 | 4.5 | 0.8 | 36 | 36.5 | 35.5 | 10 | 9.78 | 6 | 8 | 7.64 | 2 | 0.6 | 20~40 | DIN 653 |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Dimensions, material, finish and form are specified from the drawing — a screw outside the standard range is a variation on existing tooling rather than a new design. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
