Understanding Spindles in UPVC Gearboxes: Single, Split, and Dual Types

When it comes to UPVC gearboxes, understanding the three main spindle types can make all the difference. Each spindle has its strengths, making it ideal for specific situations.

Here’s how to match the right spindle to the job at hand, ensuring both functionality and security

What Is a Gearbox Spindle?

First of all, let's answer the main question. The spindle connects the internal and external door handles by passing through the gearbox. This square metal rod activates the lock mechanism when someone presses or turns the handle.

UPVC locks use three main spindle configurations: single, split, and twin. Each type serves a different purpose, so recognising which one you’re dealing with will help you work more efficiently.

How to Identify the Gearbox Spindle Type

You don’t need to remove the handles to figure out the spindle type. A quick inspection of how the door operates can tell you what you need to know:

• Single Spindle: The external handle retracts the latch without a key when the door isn’t locked.
• Split Spindle: The external handle doesn’t retract the latch unless someone unlocks the door with a key.
• Twin Spindle: The internal and external handles sit at different heights, often paired with lever/pad configurations.

Single Spindle for Simple Residential Doors

A single spindle is perfect if you require a straightforward solution for a residential door with no extra security concerns. A single spindle connects both handles through one spindle hole in the gearbox. Turning either handle moves the latch and the locking points which allows the door to open from either side. In this case, you’ll find single spindles paired with lever/lever handles, where both handles sit at the same height.

This simple design explains why it’s the most common spindle type, especially for residential properties. However, because the external handle always operates the latch, it’s not the most secure option unless the door is locked with a key.

Split Spindle for Homes Needing Extra Security

If the homeowner wants an added layer of security to prevent unauthorised access when the door isn’t locked, a split spindle can be the perfect solution.

Split spindles are designed for added security. Unlike a single spindle, this type divides the internal and external handles, so they operate independently on each side.

With a split spindle, the internal handle retracts the latch as usual, but the external handle cannot. You can only gain access from the outside with a key, even if the door is unlocked. This feature is often called a night latch function and prevents someone from simply pushing the handle to get in.

Some systems, like those from Winkhaus, use a single spindle that’s cleverly designed with a dip or washer in the middle to create the same effect. But in most cases, you’ll see two separate spindle halves sitting within a single spindle hole in the gearbox.

Twin (Dual) Spindle

A twin (also called dual or double) spindle takes the concept of independent operation further. Instead of one spindle hole, the gearbox includes two holes, typically spaced around 30mm apart. Each spindle controls one side of the door and its respective handle.

This design is common with lever/pad handles, where the internal handle operates the latch as usual, but the external pad remains fixed and cannot operate it. The handles usually sit at different heights, which makes twin spindle setups easy to identify.

When working with UPVC door locks, selecting the correct spindle type is crucial for performance and security. Check out our range of multipoint gearboxes to find the right centre case for your next job.

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