Overview
Set screws play a critical role in securing an impeller or similar component to a shaft. Proper installation ensures reliable operation, prevents slippage, and reduces the risk of equipment damage. This article outlines recommended torque ranges and key best practices for installing cup‑point set screws in Aluminum hub materials.
Purpose of Set Screws
Set screws secure the impeller to a shaft by applying pressure against the shaft surface. When two set screws are used, they are typically positioned 90° apart:
- One screw holds the key in place
- The second screw bites into the shaft to prevent movement
Common Set Screw Types
- Standard size: 5/16‑18
- Head styles: Internal hex or external square
- Tip style: Cup‑point, designed to cut into the shaft surface and prevent loosening during operation
Important: Reusing cup‑point set screws is not recommended, as worn tips reduce holding strength.
Apply Green Loctite
- Apply a drop of green Loctite to the threads.
- Green Loctite is a low-viscosity, wicking-grade anaerobic adhesive designed for sealing pre-assembled fasteners, securing set screws, and retaining cylindrical parts. It provides medium-to-high strength and is applied after assembly, utilizing capillary action to seep into threads. Common uses include preventing vibration loosening in instruments, electronics, and automotive parts.
Torque Guidelines
To ensure proper pretension and avoid damaging the hub or threads, use the following torque ranges:
- Aluminum, Cast Aluminum: Recommended torque 10–11 ft‑lbs; Maximum torque 13 ft‑lbs
Summary
Following proper torque specifications, using green Loctite, and using new cup‑point set screws will help maintain equipment safety and reliability.