Property Class 12.9 Steel Inch Slotted 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.
Property Class 12.9 Steel (ISO 898-1 property class 12.9) is the highest common strength class, for high-load machine assembly. When inch slotted shoulder screws are specified in this grade, the dimensions remain per Trade series (inch shoulder screws); the material determines corrosion behavior (requires plating or black-oxide protection) and the service temperature range (commonly limited to approx. +300 °C; confirm against the coating and the load). Both are covered below with the size table.
Why Choose Property Class 12.9 Steel for Inch Slotted Shoulder Screws
The highest common strength class, for high-load machine assembly. For inch slotted 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 |
|---|
Galvanic & Galling Considerations
For inch slotted shoulder screws in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.
Comparable Grades
For Inch Slotted 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 Slotted Shoulder Screws Available in Property Class 12.9 Steel
| Shoulder diameter (in) | Thread options | Shoulder length (in) | Slot width (in) | Slot depth (in) | Material options | Thread class |
|---|
| 1/8 | #4-40 / #6-32 | 1/8~1-1/2 | 0.047~0.094 | 0.062~0.109 | 303 or 416 stainless / alloy steel / brass | 2A |
| 1/4 | #8-32 / #10-24 / #10-32 | 1/8~1-1/2 | 0.047~0.094 | 0.062~0.109 | 303 or 416 stainless / alloy steel / brass | 2A |
| 3/8 | 1/4-20 / 5/16-18 | 1/8~1-1/2 | 0.047~0.094 | 0.062~0.109 | 303 or 416 stainless / alloy steel / brass | 2A |
| 1/2 | 3/8-16 | 1/8~1-1/2 | 0.047~0.094 | 0.062~0.109 | 303 or 416 stainless / alloy steel / brass | 2A |
Applications & Industries
Inch Slotted Shoulder Screws are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from 1/8 to 1/2 (screw size).
Industries that specify Inch Slotted Shoulder Screws
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Light machinery
Wear-resistant pivot hardware assembled with a simple slot driver.
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Linkage mechanisms
Slotted-head shoulder screws used as pivots and bearing shoulders.
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Tooling fixtures
Replaceable guide and stop points in jigs.
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Camera and instrument mounts
Controlled shoulder length where axial position matters.
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Energy & infrastructure
Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
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Maintenance & MRO
Stocked replacements matched to an existing property class, thread and finish.
Typical applications
- keeping the mating part on the shoulder instead of the threaded section
- locating a rotating or sliding part on a defined cylindrical shoulder
- selecting shoulder diameter and length separately from the thread
- using the slot for low-profile manual assembly
- joints where the property class is stated on the drawing
- clamping two machined faces to a calculated preload
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 use the slot as a high-torque structural drive; it is a compact head feature for the shoulder assembly.
- 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 Slotted Shoulder Screws are used, how to specify them, and the cases they are wrong for
