M24-3 x 130mm Hex Head Cap Screws: Class 10.9 Specs Explained

By Mutual Screw & Supply | Published: 2026-10-31

Category: How-to Guides

Learn how to read and verify the specs on M24-3 x 130mm hex head cap screws, from thread pitch to Class 10.9 markings, and avoid common ordering mistakes.

Quick answer

To confirm you have the right M24-3 x 130mm hex head cap screw, check the head marking for 10.9, verify the 3mm thread pitch with a pitch gauge, and measure 130mm from under the head to the tip. Then confirm the thread length suits your joint before installing.

Why the 3mm pitch and 130mm length matter together

M24-3 means a 24mm nominal diameter with a 3mm coarse thread pitch. That pitch affects how quickly the screw advances per turn and how it engages a matching nut or tapped hole. A 130mm length is measured from the underside of the head to the tip, not from the top of the head. If you measure from the head top, you will overestimate the length and may order a screw that bottoms out or leaves too few threads engaged.

Partially threaded vs. fully threaded: what changes for your joint

A partially threaded screw has a smooth shank below the head and threads only on the lower portion. That unthreaded shank can act as a dowel or bearing surface in shear joints, but it also means the thread length must reach through the nut or tapped hole. In a tension joint where the nut sits close to the head, a partially threaded screw may not provide enough thread engagement. Check the thread length against your clamped thickness before assuming it will work.

Zinc plating and Class 10.9: handling and environment

The zinc CR+3 plating offers mild corrosion resistance for indoor or sheltered industrial use. It is not a substitute for hot-dip galvanizing or stainless steel in wet, chemical, or outdoor exposure. Class 10.9 indicates a quenched and tempered steel with a specified minimum proof load, but the plating can affect torque values. If your application requires a precise preload, verify torque with the actual plated fasteners rather than relying on a generic table.

Step-by-step: verify M24-3 x 130mm cap screw specs before installation

Read the head marking: Look for '10.9' stamped on the head. If it is missing or illegible, treat the screw as unverified and do not assume Class 10.9 performance. A clear head marking is your first confirmation of property class.
Check the thread pitch: Use a metric pitch gauge or a known M24-3 nut. The screw should thread in smoothly by hand for several turns. A 3mm pitch is coarse; do not force a fine-thread nut onto it. If it binds immediately, you may have a different pitch—stop before damaging threads.
Measure length under the head: Measure from the underside of the head to the tip with a caliper. Confirm 130mm. Do not include the head height in your measurement. Length is always under-head for hex cap screws; measuring from the top gives a false reading.
Confirm thread length for your joint: Assemble the joint dry and check that the nut or tapped hole engages the full thread length without the unthreaded shank entering the load-bearing zone. If the shank reaches the nut, choose a different thread length. Partially threaded screws need enough thread to engage the nut fully.
Verify plating and environment: Confirm the zinc plating is acceptable for your indoor or sheltered application. For outdoor, wet, or chemical exposure, select a more corrosion-resistant finish or material. Zinc plating is not a universal corrosion solution.
Torque with the actual assembly: Use a calibrated torque wrench and the torque value specified for your joint and lubrication condition. Because plating affects friction, do not rely on a generic table without testing. When safety or preload is critical, verify torque on a sample joint first.

Product facts

M24-3 X 130mm Hex Head Cap Screws | Class 10.9 Steel Zinc Plated | Partially Threaded (10 / Pkg.): Class 10.9 steel, zinc plated, partially threaded, sold in packs of 10. This combination suits machinery and equipment assembly where a strong, moderately corrosion-resistant screw is needed, and the pack size covers small jobs without leftover stock.
M24-3 X 130mm Hex Head Cap Screws | Class 10.9 Steel Zinc Plated | Partially Threaded (10 / Pkg.)