A4 Stainless Steel Inch Hex-Socket Shoulder Screws are supplied to ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80. Corrosion behaviour is superior, including marine and chloride environments, the material is largely non-magnetic, and the usable service range is approx. -200 °C to +400 °C, subject to the property class and the joint. In practice this grade is specified for marine, coastal and chemical applications.
- Grade
- ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80
- Corrosion resistance
- Superior, including marine and chloride environments
- Magnetic response
- Largely non-magnetic
- Service temperature
- approx. -200 °C to +400 °C, subject to the property class and the joint
Property values are typical for the grade. Certified mechanical test data is available on request for production orders.
For inch hex-socket shoulder screws in A4 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) is summarized below together with every size supplied.
Why Choose A4 Stainless Steel for Inch Hex-Socket Shoulder Screws
Specified for marine, coastal and chemical applications. For inch hex-socket shoulder screws, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
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| Magnetic response | Largely non-magnetic |
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| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
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| Corrosion characteristic | Superior, including marine and chloride environments |
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Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Inch Hex-Socket Shoulder Screws in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless inch hex-socket shoulder screws: (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.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Inch Hex-Socket Shoulder Screws Available in A4 Stainless Steel
| Shoulder diameter (in) | Shoulder length (in) | Hex socket across-flats (in) | Thread series | Material options | Reference standard |
|---|
| 1/8 | 1/8~1-1/2 | 5/64~1/4 | #4-40 through #10-32 | alloy steel / 303-316 stainless / 416 stainless / brass | ASME B18.3 |
| 1/4 | 1/8~1-1/2 | 5/64~1/4 | #4-40 through 1/4-20 | alloy steel / 303-316 stainless / 416 stainless / brass | ASME B18.3 |
| 1/2 | 1/8~1-1/2 | 5/64~1/4 | #4-40 through 3/8-16 | alloy steel / 303-316 stainless / 416 stainless / brass | ASME B18.3 |
| 3/4 | 1/8~1-1/2 | 5/64~1/4 | 1/4-20 through 1/2-13 | alloy steel / 303-316 stainless / 416 stainless / brass | ASME B18.3 |
Applications & Industries
The sectors that buy Inch Hex-Socket Shoulder Screws to ASME B18.3, and the duty each one buys them for. Stocked from 1/8 to 3/4 (screw size).
Industries that specify Inch Hex-Socket Shoulder Screws
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Die and mold tooling
Guide points where the cylindrical shoulder must be held to size.
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Test fixtures
Replaceable stops and locating posts inside compact assemblies.
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Machine guards
Recessed shoulder hardware where a socket driver clears the surrounding plate.
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Robotic linkages
Socket-head shoulder screws used as repeatable pivots.
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Automotive & transport
Chassis, driveline and body fixings that see vibration and are assembled to a controlled preload.
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Steel fabrication
Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site.
Typical applications
- placing the head in a counterbore while the shoulder carries the part
- specifying shoulder length, diameter and mating thread independently
- using a positive socket drive where a slot would cam out
- providing a controlled shoulder bearing surface with a hex socket head
- bolting brackets, motors and gearboxes to a frame
- assemblies that are dismantled for service and re-torqued
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- Torque and preload
- The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.
Where to use something else
- Do not let the mating load run on the thread or socket head; the shoulder is the intended bearing feature.
- Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.
Full application guide: where Inch Hex-Socket Shoulder Screws are used, how to specify them, and the cases they are wrong for
