Tension-Control Structural Bolt Assemblies (TC / Twist-Off) manufactured in A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) are dimensioned to ASTM F3125/F3125M Grade F1852 and F2280. The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose A2 Stainless Steel for Tension-Control Structural Bolt Assemblies (TC / Twist-Off)
The most common stainless group for indoor and general outdoor fasteners. For tension-control structural bolt assemblies (tc / twist-off), 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 |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for Tension-Control Structural Bolt Assemblies (TC / Twist-Off) in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Comparable Grades
For Tension-Control Structural Bolt Assemblies (TC / Twist-Off), the alternative stainless grade is A4 (316). A2 (304) covers general indoor and outdoor service. A4 (316) adds molybdenum, which is what buys the chloride resistance for marine and de-icing-salt exposure. Where strength matters more than corrosion, plated alloy steel in class 8.8 or 10.9 is the swap to make.
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 Tension-Control Structural Bolt Assemblies (TC / Twist-Off) Available in A2 Stainless Steel
| Size | Thread series | Assembly | Minimum installation tension F1852 (lbf) | Minimum installation tension F2280 (lbf) | Finish | Reference standard |
|---|---|---|---|---|---|---|
| 1/2-13 | UNC | bolt + twist-off nut + washer | 12,550 | 15,650 | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
| 5/8-11 | UNC | bolt + twist-off nut + washer | 19,900 | 24,900 | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
| 3/4-10 | UNC | bolt + twist-off nut + washer | 29,450 | 36,800 | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
| 7/8-9 | UNC | bolt + twist-off nut + washer | 40,750 | 50,950 | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
| 1-8 | UNC | bolt + twist-off nut + washer | 53,450 | 66,800 | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
| 1-1/8-7 | UNC | bolt + twist-off nut + washer | 67,350 | 84,100 | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
| M16 | Metric option | bolt + twist-off nut + washer | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 | ||
| M20 | Metric option | bolt + twist-off nut + washer | Plain, heat-treated alloy steel | ASTM F3125/F3125M Grade F1852 and F2280 |
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. Thread size and pitch, length, property class, drive form, head geometry and head marking are all specifiable — the standard part is where it starts, not where it stops. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
