Property Class 12.9 Steel Inch Hex-Socket Shoulder Screws are supplied to ISO 898-1 property class 12.9. Corrosion behaviour is requires plating or black-oxide protection, the material is magnetic, and the usable service range is commonly limited to approx. +300 °C; confirm against the coating and the load. In practice this grade is the highest common strength class, for high-load machine assembly.
- Grade
- ISO 898-1 property class 12.9
- Corrosion resistance
- Requires plating or black-oxide protection
- Magnetic response
- Magnetic
- Service temperature
- commonly limited to approx. +300 °C; confirm against the coating and the load
Property values are typical for the grade. Certified mechanical test data is available on request for production orders.
Inch Hex-Socket Shoulder Screws manufactured in Property Class 12.9 Steel (ISO 898-1 property class 12.9) are dimensioned to ASME B18.3. 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 Property Class 12.9 Steel for Inch Hex-Socket Shoulder Screws
The highest common strength class, for high-load machine assembly. For inch hex-socket shoulder screws, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 12.9 |
|---|
| Magnetic response | Magnetic |
|---|
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
|---|
| Corrosion characteristic | Requires plating or black-oxide protection |
|---|
Corrosion Behavior in Service
Carbon and alloy steel inch hex-socket shoulder screws require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Comparable Grades
For Inch Hex-Socket Shoulder Screws, class 8.8 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of Inch Hex-Socket Shoulder Screws Available in Property Class 12.9 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.
-
Machine guards
Recessed shoulder hardware where a socket driver clears the surrounding plate.
-
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
