ASTM F835 Alloy Steel Socket Button and Flat Head Cap Screws
The low-head socket screws: button and flat countersunk heads in alloy steel at 144 ksi (½ in. and smaller) and 136 ksi above, 37 to 44 HRC — rated below A574 because the shallow head, not the shank, limits the load.
What F835 is.
ASTM F835 covers socket button head, socket flat countersunk head and socket low head cap screws in alloy steel (button 0.060 to 0.625 in., flat 0.060 to 1.5 in., low head 0.1120 to 0.625 in.). The steel and hardness are the same as A574, but the tensile minimums are lower, 144 ksi at ½ in. and smaller and 136 ksi above, because the shallow head cannot develop the full strength of the shank. The screws are black oxide finished and dimensioned to ASME B18.3.
We machine F835 button and flat head screws in special lengths and threads from certified alloy bar, heat treated and black oxided.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | 0.30 | 0.48 |
| Phosphorus | P | — | 0.035 |
| Sulfur | S | — | 0.040 |
| Alloying elements | — | required | — |
Values per ASTM F835-23 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Grade / condition and size | Tensile strength, min (ksi) | Yield or proof, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| ½ in. and smaller (full size) | 144 | — | — | — | 39–44 HRC |
| Over ½ in. (full size) | 136 | — | — | — | 37–44 HRC |
| Machined specimen, over ½ in. | 170 | 153 | 8 | 35 | 37–44 HRC |
Values per ASTM F835-23 Table 1 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Specifications that apply.
How F835 ships from Houston.
- Hex and heavy hex bolts and cap screws
- Studs and threaded rod
- Nuts and washers to match
- Machined specials to drawing
F835 fasteners we make.
Every item is manufactured to your drawing or standard in F835, imperial or metric, with an EN 10204 3.1 certificate.
Why F835 is rated below A574
A button or countersunk head is shallow, so the socket takes up most of it and the head can shear or the socket can strip before the shank reaches its full strength. F835 therefore sets the tensile minimum about 20 percent below A574 while keeping the same steel and hardness, and it does not specify a proof load. Where the joint needs the full 170 ksi, use a socket head cap screw.
Testing, certification and marking
- Tensile and hardness per lot to ASTM F606
- Manufacturer's identification on the head where size allows
- Certificate of conformance or test report with heat number
- Hydrogen embrittlement bake after any plating
Recent F835 jobs.
ASTM A574 Alloy Steel Socket Head Cap Screws (170–180 ksi)
The socket head cap screw specification: alloy steel quenched and tempered to 180 ksi in ½ in. and smaller and 170 ksi above, 37 to 44 HRC, black oxide — the standard for tooling, machinery and die work.
ASTM F879 · ASME B18.3ASTM F879 Stainless Steel Socket Button and Flat Head Cap Screws
The stainless low-head socket screws: button and flat countersunk heads in 304 or 316, annealed at 85 ksi maximum or cold worked to 80 and 102 ksi minimum, passivated.
ASTM F912 · ASME B18.3ASTM F912 Alloy Steel Socket Set Screws
The socket set screw specification: alloy steel through hardened to 45 to 53 HRC, torque tested rather than tensile tested, with cup, flat, cone, oval and half-dog points — black oxide finished.