How to Fit a Rim Lock Door Knob

Author: Carl Benson

Carl is the founder of Suffolk Latch Company, with a background in engineering and over 20 years’ experience in home hardware. He works closely with suppliers and designers alike to develop quality ironmongery that stands the test of time. Read my full bio.

How to Fit a Rim Lock Door Knob

Fitting a rim lock door knob is different from fitting a standard mortice door knob or concealed rose door knob. The parts go together in a specific way, and the alignment between the rim lock, threaded bar, locating component and rose plate is important.

This guide follows Carl’s fitting video and explains the main stages: checking the supplied parts, measuring the rim lock backset, marking the door, drilling the spindle hole, fitting the rim lock and threaded bar, fixing the rose plate and adjusting the second knob.

The demonstration focuses on the door knob fitting process. It does not cover fitting the keyhole, keep or strike plate in detail. If you are still deciding which type of door knob setup is right for your door, you may also find our guide to Rim Lock vs Mortice Door Knobs useful.

Table of Contents

Before You Start

Before starting, make sure you understand the parts supplied with the rim lock door knob set. Rim lock knobs are quite specific in the way they are assembled. The small parts matter, and it is easy to get confused if you remove everything from the packaging without keeping it organised.

Use a small container for screws, nylon washers, Allen keys and small fixing parts. This is especially useful if you are working on a building site, renovating a room or fitting several sets at once.

You should also check whether you are fitting the knobs to a new door or replacing old hardware on an existing door. Existing holes are not always in the right position for a new rim knob set, so do not assume that old spindle holes will automatically suit the new hardware.

Watch the Fitting Video

Carl’s video shows the full fitting process for this rim lock door knob system, from unboxing the supplied parts through to final adjustment.

Captions have been requested in the embed where an English caption track is available. If captions do not display automatically, use the YouTube controls on the video player.

Check the Parts Before You Start

Start by unpacking the rim lock door knob set and laying out the component parts. In the demonstration, Carl shows the knobs, screws, nylon washers, Allen key, threaded bar, fixing plate and small locating component.

Keep these smaller parts safe. A missing washer, screw or grub screw can stop the fitting process, and small parts are easy to lose between floorboards or among tools.

The threaded bar and locating component are particularly important. They are not decorative extras. They form part of the way the rim knob is supported, aligned and adjusted.

Measure the Rim Lock Backset

The backset is the distance from the front face of the rim lock to the centre of the spindle opening. It is the measurement that tells you where the spindle hole needs to be drilled in the door.

In Carl’s demonstration, the rim lock backset measures approximately 105 mm. This is the measurement for the lock used in the video. Always measure your own rim lock before marking or drilling your door.

Take the measurement carefully from the face of the rim lock to the centre of the spindle opening. Once this measurement is wrong, every following step becomes harder to correct.

Mark the Door Carefully

Once you know the backset, mark the centre line on the door. Use a square to transfer the line accurately across the door face and around to the opposite side where required.

In the video, Carl uses the square to mark the horizontal line and then sets out the backset position. He also accounts for pencil thickness while marking. The important point is not the exact adjustment he makes in the demonstration, but that your final mark must be accurate.

Mark both sides of the door so the spindle position lines up properly. If the two sides are out of line, the knob may feel tight, uneven or difficult to adjust.

Drill the Locating Hole

The small locating component is one of the most important parts of this fitting method. In the demonstration, Carl measures this component at 12 mm and drills a matching 12 mm hole so that it can sit accurately in the door.

Check the supplied component before drilling. The aim is for the locating part to sit neatly and accurately, without unnecessary movement.

Use a centre punch or accurate pilot mark before drilling. This helps stop the drill bit from wandering and keeps the hole aligned with your measured backset and centre line.

Fit the Rim Lock and Threaded Bar

With the hole drilled, position the rim lock and pass the knob’s threaded bar through the rim lock and the door. In the demonstration, Carl places a nylon washer over the square shank before passing the bar through.

The washer and threaded bar need to sit correctly because the bar forms the working connection between the knobs. This is what allows the rim knob system to turn and operate the lock cleanly.

Do not fully tighten or force anything at this stage. The aim is to bring the parts together accurately so the opposite-side fixing can be aligned before final adjustment.

Secure the Locating Component

On the opposite side of the door, the small locating component is wound onto the threaded part until it sits against the door face. This component then acts as the guide for the rose plate and helps keep the assembly aligned.

Once it is seated correctly, fix it in place with the small screws supplied. In the demonstration, Carl secures it with two small screws.

This stage is important because the locating component supports the clean operation of the rim knob. If it is not seated correctly, the rose plate and second knob may not sit properly.

Fit the Rose Plate

The rose plate then fits over the locating component. In the demonstration, the rose has a carefully machined recess that sits over the locating part so the visible rose can sit flush against the door.

Align the rose plate with your centre marks before drilling the fixing holes. Use a self-centring pilot bit if available, as this helps keep the screw holes centred in the countersunk holes of the plate.

Once the holes are prepared, secure the rose plate to the door. Check that it sits flat and that the threaded bar still turns cleanly.

Fit and Adjust the Second Knob

With the rose plate fixed, the second knob can be wound onto the protruding mortice bar. Turn it down gently by hand until it sits correctly against the rose.

The mortice bar has flat faces. The grub screw should tighten onto one of these flats rather than onto a corner or random edge. This gives the grub screw a better seating point and helps secure the knob properly.

In the demonstration, Carl raises the knob slightly, checks the tension and then tightens the grub screw with the Allen key once he knows it is sitting on a flat of the bar.

The bars are supplied slightly long. On thinner doors, they may need to be trimmed. For thicker doors up to around 44 mm, the demonstration explains that the supplied length is normally suitable.

Check the Final Operation

Once fitted, test the knob from both sides. The movement should feel clean and controlled, without binding or grinding.

If the knob does not turn smoothly, check the alignment before tightening anything further. The key points are the backset, the centre line, the drilled locating hole, the position of the rim lock and the way the second knob is fixed to the mortice bar.

The finished result should give a clean visible rose with no exposed rose screws on the finished side shown in the demonstration.

Useful Video Timestamps

Use these points in the video to find the main fitting stages quickly:

• 00:00: Introduction
• 01:00: Door knobs and supplied fittings
• 03:35: Preparing the door and tools
• 04:45: Measuring and marking the door
• 06:20: Drilling the spindle hole
• 07:30: Positioning the rim lock and spindle
• 09:20: Fitting the rose on the opposite side
• 11:20: Fitting and adjusting the second knob
• 12:20: Finished fitting

Related Guides

These related guides may help if you are choosing between door knob types or fitting other parts of the door hardware:

• Rim Lock Door Knobs Explained
• Rim Lock vs Mortice Door Knobs
• Door Knobs and Backset Explained
• Door Knobs Explained
• How to Choose Door Knobs

Conclusion

Fitting a rim lock door knob is mainly about careful measuring and alignment. The parts need to be assembled in the correct order, and the small locating component plays an important role in keeping the rose plate and knob properly positioned.

Measure your own rim lock backset, mark both sides of the door accurately, drill the locating hole carefully and check the final movement before tightening everything fully.

If the rim lock, spindle, locating component, rose and second knob are aligned correctly, the knob should operate smoothly and leave a clean finished appearance.

FAQ

Do I need to measure my own rim lock before fitting the knob?

Yes. Always measure the backset of your own rim lock before marking or drilling. The demonstration uses a rim lock with a backset of about 105 mm, but that measurement should not be assumed for every rim lock.

What is the backset on a rim lock?

The backset is the distance from the front face of the rim lock to the centre of the spindle opening. It determines where the spindle hole should be positioned in the door.

Why does the small locating component matter?

The locating component helps position and support the opposite-side rose. In the demonstration, it fits into a matching drilled hole and is then secured to the door, helping the rose and knob sit correctly.

Do I always need to drill a 12 mm hole?

In the demonstration, Carl measures the supplied locating component at 12 mm and drills a matching 12 mm hole. Check the supplied component and product instructions before drilling, especially if your fitting set differs.

Can I fit rim lock door knobs to an existing door?

Yes, but existing holes may not be in the correct position for the new rim lock knob set. Check the backset, centre line and spindle position before relying on old holes.

Where should the grub screw tighten?

The grub screw should tighten onto one of the flat faces of the mortice bar. This helps secure the knob properly and avoids tightening randomly onto an edge.