Metric Class 10.9 Zinc Plated Steel Hex Tap Bolts
Class 10.9 zinc plated hex tap bolts combine high-strength steel construction with a protective zinc coating for demanding structural and mechanical applications. Also known as hex cap screws or partial thread bolts, these fasteners feature a hexagonal head for standard wrench installation and an unthreaded shank section that improves shear performance and reduces stress concentration at the joint interface. With approximately 1,040 MPa tensile strength, Class 10.9 is the highest common metric bolt grade and serves as the direct equivalent to SAE Grade 8 in inch-series fastening. Whether you are assembling heavy equipment frames, securing critical automotive drivetrain components, or bolting together structural steel connections, Class 10.9 zinc plated hex tap bolts provide the clamping force and corrosion protection needed to maintain joint integrity under severe loading conditions.
How Hex Tap Bolts Work
Hex tap bolts thread into a tapped hole or through a clearance hole with a nut on the opposite side. The hexagonal head provides a positive drive surface for wrenches, ratchets, and sockets, allowing high installation torque without cam-out. What distinguishes a tap bolt from a fully threaded bolt is the unthreaded shank section directly below the head. This smooth shank acts as a dowel pin within the joint, carrying shear loads through the solid bolt body rather than across the threads. The result is improved fatigue resistance, better load distribution, and stronger performance in applications where lateral forces act on the fastened connection. Thread engagement begins only within the tapped hole or nut, keeping the highest-stress clamping zone free of thread root stress risers.
Why Choose Class 10.9 Steel
Class 10.9 is a quenched and tempered alloy steel grade that delivers approximately 1,040 MPa tensile strength and a minimum proof load of 830 MPa. This places it well above Class 8.8 general-purpose bolts, which reach approximately 800 MPa tensile. The higher strength allows engineers to use smaller diameter fasteners for equivalent clamping force, saving weight and space in compact assemblies, or to maintain the same bolt size with a significantly higher safety margin. Class 10.9 fasteners are specified throughout automotive, heavy equipment, agricultural, and industrial sectors wherever standard-grade bolts cannot meet the load requirements of the joint design.
Zinc Plated Finish
The zinc plated finish on these hex tap bolts provides an electrodeposited barrier coating that protects the underlying high-strength steel from moisture, mild chemicals, and atmospheric corrosion. Zinc plating is RoHS compliant and offers reliable performance in indoor environments, sheltered outdoor installations, and applications where the bolt will receive additional coatings or paint after assembly. The finish also provides a uniform, professional appearance and reduces galling during installation. For applications requiring enhanced corrosion protection in harsher or fully exposed outdoor environments, consider upgrading to a hot-dip galvanized or stainless steel alternative.
Coarse Thread vs. Fine Thread
Class 10.9 zinc plated hex tap bolts are available in both coarse and fine thread pitches. Coarse thread is the standard metric default, offering faster installation, better tolerance of slightly damaged or dirty threads, and strong performance across general-purpose structural and mechanical applications. Fine thread pitches feature a tighter helix angle with more threads per unit length, which increases tensile strength for a given diameter, provides greater resistance to vibrational loosening, and allows finer torque adjustment during installation. Fine thread tap bolts are commonly specified for precision machinery, automotive engine and suspension assemblies, hydraulic systems, and any application where vibration resistance or precise clamping control is critical.
Common Applications
- Automotive & Motorsports – Engine mounts, suspension components, drivetrain assemblies, and chassis connections requiring high tensile strength and vibration resistance
- Heavy Equipment & Machinery – Frame bolting, boom pivot connections, and structural joints on excavators, loaders, cranes, and industrial machinery
- Agricultural Equipment – Implement frames, hitch assemblies, and structural mounting points on tractors, harvesters, and tillage equipment
- Construction & Infrastructure – Structural steel connections, bridge components, tower assemblies, and heavy-load bearing joints
- Industrial & Manufacturing – Press frames, conveyor structures, motor mounts, and production equipment subject to high static and dynamic loads
- OEM & Custom Fabrication – Specifying high-strength metric fasteners for engineered assemblies, prototype builds, and custom machinery
Available Sizes
Albany County Fasteners stocks Class 10.9 zinc plated hex tap bolts across a range of metric diameters in both coarse and fine thread pitches, with multiple lengths available in each size. Coarse thread options cover standard metric pitches for general-purpose high-strength bolting, while fine thread options provide the tighter pitch needed for vibration-sensitive and precision applications. Browse the listings below to find the specific diameter, thread pitch, and length combination for your project.
Need help selecting the right Class 10.9 hex tap bolt for your application? With over 18 million fasteners in stock and competitive bulk pricing, Albany County Fasteners is ready to help. Contact our team for technical assistance, volume quotes, or to discuss your high-strength metric bolting requirements.