A2 Stainless Steel Thumb Nuts (Type A) are supplied to our own published dimensions — this is a trade-series article rather than one covered by a dimensional standard, so confirm the figures against the part you are replacing. The grade provides good general corrosion resistance and is largely non-magnetic; the practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint.
Why Choose A2 Stainless Steel for Thumb Nuts (Type A)
The most common stainless group for indoor and general outdoor fasteners. For thumb nuts (type a), 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 thumb nuts (type a): (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 Thumb Nuts (Type A), 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
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Thumb Nuts (Type A) Available in A2 Stainless Steel
| Thread size | Blade width B (mm) | Blade height H (mm) | Base diameter (mm) | Thickness (mm) | Reference standard |
|---|---|---|---|---|---|
| No.6-32 | 15.9 | 9.5 | 7.9 | 1.5 | Industry standard |
| No.8-32 | 17.5 | 10.3 | 9.5 | 1.5 | Industry standard |
| No.10-24 | 19.1 | 11.1 | 10.3 | 1.9 | Industry standard |
| 1/4"-20 | 22.2 | 12.7 | 12.7 | 1.9 | Industry standard |
| 5/16"-18 | 25.4 | 14.3 | 14.3 | 2.4 | Industry standard |
| 3/8"-16 | 28.6 | 15.9 | 15.9 | 2.4 | Industry standard |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this nut in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. A non-standard nut is quoted from the drawing; where one already exists in the catalog, the special is usually a variation on its tooling. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
