Before You Begin: Tools and Preparation

Fitting a new door knob is one of those satisfying jobs that transforms a door with minimal fuss. But before you pick up a screwdriver, gather the right tools. You will need a tape measure, a pencil, a bradawl or small nail, a drill with bits (typically 8mm, 10mm, and a hole saw or flat bit for the latch), a chisel, a hammer, a hacksaw, a screwdriver, and an Allen key (often supplied with the knob).

• Safety glasses – essential when drilling
• Masking tape – to reduce splintering
• Wooden block or drill guide – to keep bits straight
• Graphite powder – for lubricating the latch later

Safety first: wear safety glasses, especially when drilling, and ensure the door is firmly wedged open or removed and supported. If you are replacing an existing knob, check whether the old latch and spindle are reusable; often it is easier to replace the whole set. Also, decide whether you want a knob on a rose (a small circular plate) or a backplate (a larger rectangular plate). Both are common in British homes, but backplates suit older or period properties.

Choosing the Right Door Knob and Spindle

The spindle is the square metal bar that connects the two knobs through the door. Most UK door knobs use an 8mm square spindle, but some older or heavy-duty sets use 10mm. Always check the knob's specification. Spindles come in standard lengths, often 100mm or 120mm, but you will almost always need to cut yours to size. The material matters too: brass, stainless steel, or zinc alloy. For a classic British look, polished brass or antique bronze works well. Consider the weight of the knob; heavy solid brass knobs feel lovely but need a sturdy latch. If you have a mortice lock rather than a tubular latch, the spindle passes through the lock follower. In that case, ensure the spindle is long enough to engage both knobs but not so long that it juts out. A good rule of thumb: the spindle should extend about 15mm into each knob.

Measuring Your Door and Spindle Length

Measure the thickness of your door in millimetres. A standard internal door is 35mm, while external or fire doors are often 44mm or 54mm. To calculate the correct spindle length, take the door thickness and add 30mm. For example, a 35mm door needs a spindle around 65mm long. This allows roughly 15mm of spindle to enter each knob. If your knob has a deep rose or backplate, add a little more—measure the depth of the knob's spindle hole and double it, then add the door thickness. Write this measurement down. Next, measure the backset: the distance from the edge of the door to the centre of the spindle hole. For a tubular latch, common backsets are 44mm or 57mm. If you are fitting a new latch, choose a backset that matches your existing holes, or drill fresh. Mark the centre of the spindle hole on both faces of the door using a bradawl. Ensure the marks align perfectly; a small pilot hole through the door can help you check alignment from both sides.

Safe Drilling Techniques for a Neat Fit

Drilling is where care pays off. Start by drilling the spindle hole (usually 8mm or 10mm) through the door from both sides to avoid splintering. Use a piece of masking tape over the mark to reduce tear-out. Drill at a slow speed with a sharp bit, and keep the drill perpendicular to the door face. For the latch body, you need a hole in the edge of the door, typically 22mm or 25mm diameter, centred at the same height as the spindle hole. The two holes must intersect cleanly. A drill guide or a simple wooden block clamped to the door can help you keep the bit straight. Drill the edge hole first, then the face hole, or vice versa—just go slowly. If you are using a chisel to mortice the latch faceplate, score the outline lightly, then chisel away a shallow recess so the plate sits flush. Always wear safety glasses and unplug your drill before changing bits. Take your time; a ragged hole is hard to hide.

Fitting the Knob and Final Adjustments

Insert the tubular latch into the edge hole, with the curved side of the latch bolt facing the door frame (the direction the door closes). Screw the faceplate to the door edge. Now push the spindle through the latch follower. It should slide in easily but not wobble. If it is too long, cut it with a hacksaw, ensuring the ends are square and free of burrs. Fit one knob onto the spindle, aligning the grub screw hole with the flat on the spindle (if present). Tighten the grub screw with the Allen key, but not so tight that you strip the thread. Then fit the second knob on the other side, checking that both knobs turn smoothly and the latch retracts fully. If the knob has a rose, screw it to the door through the provided holes. Finally, fit the strike plate on the door frame so the latch clicks neatly into place. Test the door several times. If the knob feels stiff, loosen the grub screws slightly or lubricate the latch with a little graphite powder. With these steps, you will have a neatly fitted door knob that feels solid and works beautifully for years to come.