Metric Class 10.9 Plain Alloy Hex Tap Bolts
What are metric Class 10.9 plain alloy hex tap bolts? Metric Class 10.9 plain alloy hex tap bolts are fully threaded metric hex cap screws made from quenched and tempered alloy steel, left with a plain uncoated finish. Class 10.9 is the highest common metric bolt grade, roughly 1,040 MPa tensile, and the metric equivalent of SAE Grade 8, for high-strength joints.
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What does Class 10.9 mean on a hex tap bolt?
Class 10.9 is a metric strength grade: the numbers indicate roughly 1,040 MPa minimum tensile strength and an 830 MPa proof load, making it the highest common metric bolt class and the direct counterpart to SAE Grade 8 in the inch world. The strength comes from quenched and tempered alloy steel, so a Class 10.9 bolt lets you carry heavier loads at a given diameter, or keep the same size with more safety margin, in automotive, heavy equipment, agricultural, and industrial joints. Tap bolt means the bolt is fully threaded, so it works like a hex cap screw that threads all the way into a tapped hole or takes a nut anywhere along its length. The plain finish is clean and uncoated, ideal for indoor or controlled environments, or where the bolt will be oiled, painted, or otherwise protected after assembly. Because plain alloy steel has no corrosion coating, it is best kept out of wet or outdoor exposure. For those conditions, choose the zinc plated Class 10.9 version.
Why choose metric Class 10.9 plain alloy hex tap bolts
- Highest common metric grade: about 1,040 MPa tensile, the Grade 8 equivalent.
- Quenched and tempered alloy steel: high strength for demanding joints.
- Fully threaded: tap bolt engages a tapped hole or nut anywhere along the length.
- Plain finish: clean uncoated surface for indoor or protected use.
Common applications for Class 10.9 plain alloy hex tap bolts
- Automotive and drivetrain assemblies
- Heavy equipment and machinery frames
- Agricultural and industrial machinery
- High-strength structural and mechanical joints
For corrosion resistance in wet or outdoor use, see metric Class 10.9 zinc plated hex tap bolts, and browse every grade on the main hex tap bolts category.
Metric Class 10.9 Plain Alloy Hex Tap Bolts FAQ
Is Class 10.9 the same as Grade 8?
They are close contextual equivalents. Class 10.9 has about 1,040 MPa tensile strength, matching SAE Grade 8, though the two follow different metric and inch standards and testing. Treat them as equivalent in strength, not as interchangeable specifications.
What does plain alloy finish mean?
The bolt is uncoated quenched and tempered alloy steel. It suits indoor or controlled environments and joints that will be oiled or painted. Plain steel can rust in damp or outdoor use, so choose zinc plated for corrosion resistance.
What is a tap bolt?
A tap bolt is a fully threaded hex cap screw. The full-length thread lets it thread into a tapped hole or take a nut at any point, unlike a partially threaded bolt with a plain shank.
What is the American equivalent standard?
ASTM A354 Grade BD covers quenched and tempered alloy steel bolts with properties closely matching Class 10.9, and full-thread metric tap bolts follow DIN 961.