Multiquip 21678 Flat Head Socket Cap Screw 5/16-24 x 1-3/4

The Multiquip 21678 is a genuine OEM Flat Head Socket Cap Screw 5/16-24 x 1-3/4 designed for a wide range of Multiquip and Whiteman walk-behind power trowels, including JS36, J36, CA4HC, B46S90, and CS24 series machines. As a direct OEM replacement, this fastener is manufactured to the exact thread pitch, head profile, and dimensional tolerances required by Multiquip for correct installation. Sourcing the correct screw by part number 21678 ensures the fastener seats flush and torques down properly without the guesswork of aftermarket substitutions. DHS Equipment stocks this genuine OEM part to keep your trowel on the slab and performing as intended.

Key Features

• Exact Thread Specification: — 5/16-24 fine-thread pitch matches the tapped holes in the trowel assembly precisely, ensuring full thread engagement and correct clamp load.
• Flush-Mount Flat Head Profile: — The flat head socket cap design seats countersunk into the component surface, preventing interference with moving parts and maintaining the correct operating clearance on the trowel.
• Genuine OEM Sourcing: — Manufactured to Multiquip's original material and dimensional specification — not an approximated substitute — so the fastener performs exactly as the machine was designed to require.
• Broad Trowel Family Fitment: — Confirmed for JS36, J36, JA, CA, and B46 series walk-behind power trowels, including both Multiquip and Whiteman-branded models across multiple configurations.
• Fastener Integrity Supports Blade Control: — A loose or incorrect screw in a trowel assembly can allow components to shift under vibration, affecting blade pitch consistency and finish quality on the slab. The correct part holds everything in spec.

A flat head socket cap screw is a precision fastener used where a flush or countersunk mounting surface is required — common in rotating or close-tolerance assemblies like walk-behind power trowels where protruding fastener heads would create clearance issues or snag hazards. The 5/16-24 designation refers to a 5/16-inch diameter with a 24-thread-per-inch fine-thread pitch, which provides higher clamping force and better resistance to loosening under vibration compared to coarse-thread equivalents. When this fastener is stripped, missing, or replaced with an incorrect substitute, the connected components can shift or work loose during operation, compromising trowel performance and potentially damaging the surrounding assembly.

Part Details

Compatibility & Fitment

Verify Before You Order

Fitment is machine-number and revision-specific; always confirm your model and serial number against the fitment list.

Why Buy From DHS Equipment

Every part is verified against the manufacturer's part number before it ships, so what you order is what arrives. We carry parts from leading OEM brands and our own DHS Quality Parts line of professional aftermarket components. Need help finding the right part? Our team is available to confirm compatibility whenever you need it. Orders are processed fast to keep your jobs on track. We don't just sell parts. We keep you jobsite ready.

Questions? Contact our team at [email protected] or 866-611-9369 — DHS Equipment is here to help you maintain peak performance.