Spindle Hole Size Guide for Simpled Smart Locks

One question we’re sometimes asked is:

“Will this lock fit my existing door?”

In most cases, yes — installation is straightforward.

However, there is one small detail worth checking: the size of the spindle hole in your door.

What Is the Spindle Hole?

The spindle hole is the round hole through the door where the handle spindle passes.

If this hole is slightly too small, internal parts of the smart lock can sit too tightly against the edge of the door. Over time, this may cause minor rubbing or stiffness when operating the handle.

This is not common — but it’s worth checking for a smooth installation.

Minimum Hole Size Required

Here’s the minimum diameter needed for each model range:

• SF / SFS models – Minimum 24mm
• EF / DFF / SS / TF models – Minimum 18mm

If your door meets these measurements, you should not experience any issues.

A Note About Some Composite Doors

Some composite door brands — including reports from installers working with Rockdoor — may have slightly smaller spindle holes than required for our SF / SFS range.

In these cases, the hole may need to be widened slightly during installation to allow proper clearance.

If the hole is too tight, the outer spindle cup may rub against the inside of the hole. Over time, this could affect alignment. Ensuring the correct diameter prevents this.

What If My Hole Is Slightly Too Small?

If the hole is only slightly undersized, it can often be carefully adjusted to the required diameter.

If you’re unsure or prefer not to modify the door:

• You can contact us before ordering and we’ll help you check compatibility.
• If you’ve already ordered and the item is unused, we’re happy to assist with a refund.