A 3-Minute Guide to Permissible Axial & Radial Loads

Your Reducer's Output Shaft is Not a Steel Rod: A 3-Minute Guide to Permissible Axial & Radial Loads

When selecting a reducer gearbox for your equipment, do you only look at power, reducer ratio, and model number before placing an order?

If yes, you might be stepping into a critical trap. This oversight can lead to anything from leaks and noise to catastrophic reducer failure. It often hides in the corner of the specification sheet, named Permissible Axial Load and Permissible Radial Load.

Don't let the terms intimidate you. Let's use a simple analogy with your arm to understand it instantly.

1. What Exactly Are They?

Imagine the output shaft of your speed reducer is like your arm.

Axial Load: This is like someone pushing or pulling your hand directly along the length of your arm (from shoulder to palm). This force tries to retract your arm or pull it out of its socket.

In Machinery: This commonly occurs with helical or worm gears, or from misaligned couplings/pulleys, creating a push/pull force along the shaft centerline.

Radial Load: This is like someone side-loading your wrist while shaking your hand. This force tries to bend your arm sideways.

In Machinery: This is extremely common! Belt drives (tension force), chain drives, or even a heavy gear/sprocket mounted on the shaft creates this perpendicular, "bending" force.

2. What Does "Permissible" Mean? – It's the Performance Limit

"Permissible" means "allowed." The Permissible Axial/Radial Load is the manufacturer's warning: "This shaft can handle only so much push/pull or side force. Exceed this limit, and I can't guarantee proper operation or longevity!"

This is NOT the shaft's ultimate breaking point. It is a safe operational value determined by the combined limits of the internal bearings, seal integrity, and gear alignment.

If you're curious to learn more about gear reducers or gearmotors. Leave me a message—I'm here to help.