A286 Socket Head Cap Screws

A socket head cap screw carries a high clamp load through a small head. That works in alloy steel at room temperature, but alloy steel loses strength and scales as the temperature climbs. Standard 300-series stainless keeps its corrosion resistance but has only a fraction of the strength. A286 bridges that gap.

• Strength at temperature. Titanium and aluminum form a strengthening precipitate during aging, so A286 keeps useful strength up to about 1300 °F.
• Thermal expansion close to austenitic stainless. ASTM A453 was written for bolting whose expansion matches austenitic stainless steel, which helps joints in 300-series flanges and housings keep their preload through heat cycles.
• Cryogenic toughness. A286 stays tough at very low temperatures and is non-magnetic, so it suits cryogenic and instrument assemblies.
• Corrosion resistance. Its chromium and nickel content resists oxidation and many corrosive environments far better than coated alloy steel.

Grade 660 comes in four classes. The chemistry is the same in all four; the solution and aging heat treatments differ. Order the class your design calls for, and we machine and certify to it.

Aerospace drawings often call out AMS bar specifications instead. AMS 5732 and AMS 5737 cover A286 bar in different solution-treatment conditions. Send your drawing and we will match the material, condition and testing it lists.

Limits vary slightly between ASTM A453 and the AMS specifications. The mill test report for your heat is the controlling document.

• Dimensions: ASME B18.3 inch socket cap screws, or made to your drawing.
• Threads: Inch series, Class 3A per ASME B18.3.

A286 can gall, especially against itself or stainless mating threads. Use a thread lubricant suited to the service temperature.

• Gas turbines and power generation: Casing, combustor and exhaust bolting that runs above alloy-steel limits. See Power Generation.
• Aerospace: Engine and airframe hardware where strength, temperature and non-magnetic properties all matter. See Aerospace.
• Oil and gas: Valve, wellhead and subsea assemblies, where Class D is commonly specified. See Oil & Gas.
• High-temperature valves and pressure vessels: Flange and bonnet bolting in austenitic stainless equipment.
• Cryogenic and instrument equipment: LNG, test rigs and other assemblies that need a non-magnetic fastener.

Patriot Bolt is ISO 9001:2015 certified. Each A286 order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification and class on your purchase order.

Compare A286 with other high-temperature grades in our Fastener Materials Matrix.

Is A286 the same as Alloy 660?

Yes. A286, Alloy 660, Grade 660 and Incoloy A-286 all refer to the same alloy, UNS S66286. “Grade 660” is the ASTM A453 bolting designation.

What temperature can A286 socket head cap screws handle?

A286 keeps its strength and oxidation resistance to about 1300 °F and stays tough at cryogenic temperatures. The actual design limit depends on the joint, preload and code your project follows.

Which Grade 660 class should I order?

Classes A, B and C share the same minimum properties and differ in heat treatment. Class D has a higher yield strength and a lower maximum hardness, and it is often called out for oil and gas service. Follow your drawing or code, or send us the application and we will help you choose.

Is A286 magnetic?

No. A286 is austenitic and essentially non-magnetic, which is one reason it is used in instrument and aerospace assemblies.

Can you match nuts, studs and washers?

Yes. We also machine A286 nuts, stud bolts, hex head cap screws, 12-point flange bolts and shoulder bolts, so the whole joint can be ordered from one source.