The Multiquip 21583 HHC Screw 5/16-24 x 1.50 Grade 8 is a genuine OEM fastener designed for HTX44 and STX55 series hydrostatic ride-on power trowels. As a direct Multiquip replacement, part 21583 meets the exact thread specification, length, and hardness grade required for the original assembly. This screw is confirmed for use on HTX44K4, HTX44K5, HTX44Y4, HTX44Y5, and STX55Y6 models, giving you confidence that you are ordering the correct hardware for your machine. Sourcing OEM fasteners like the Multiquip 21583 ensures the joint integrity and clamping force the manufacturer engineered into the original design.
Key Features
- Grade 8 Hardness Rating — Meets the high tensile strength requirement for structural fastener applications on heavy-duty ride-on trowel assemblies, where undertorqued or incorrect-grade hardware can cause joint failure under vibration.
- Correct Thread and Length Specification — 5/16-24 fine-thread pitch and 1.50-inch length match the OEM hole pattern and engagement depth exactly, threading in without modification.
- Genuine Multiquip OEM Part — Sourced directly through Multiquip's authorized parts network, so the alloy grade, heat treatment, and dimensional tolerances align with what left the factory originally.
- Confirmed Fitment for HTX44 and STX55 Series — Verified for HTX44K4, HTX44K5, HTX44Y4, HTX44Y5, and STX55Y6 hydrostatic ride-on trowels — no guesswork on compatibility.
- Vibration-Resistant Clamping Performance — Fine-thread fasteners maintain clamp load better under the sustained vibration generated by trowel blade operation, helping assembled components stay secure through heavy finishing cycles.
An HHC (hex head cap) screw is a standard structural fastener used throughout the frame, blade assembly, and drive components of ride-on power trowels to clamp mating parts securely together. The Grade 8 designation indicates a high-strength alloy with a minimum tensile strength suited to joints that experience significant mechanical stress and vibration during trowel operation. When a fastener in this application is missing, damaged, or replaced with an incorrect grade or thread pitch, the clamping force in that joint drops — which can allow components to shift, loosen further under vibration, or cause accelerated wear to the surrounding hardware and mating surfaces.
Part Details
| Part Number | 21583 |
|---|---|
| Brand | Multiquip |
| Part Type | Genuine OEM |
| Description | HHC Screw 5/16-24 x 1.50 Grade 8 |
Compatibility & Fitment
| Name | Model |
|---|---|
| Whiteman Ride-On Power Trowels | HTX44K4 |
| Whiteman Ride-On Power Trowels | HTX44K5 |
| Whiteman Ride-On Power Trowels | STX55J6 |
| Whiteman Ride-On Power Trowels | HTX44Y4 |
| Whiteman Ride-On Power Trowels | HTX44Y5 |
| Whiteman Ride-On Power Trowels | STX55Y6 |
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.
