How to drill a bigger hole to fit a knobset

Changing from a Tubular to a Cylindrical Knobset

Swap fitting a new knobset in place of an old knobset is usually a straight forward job and just about anyone can do. But sometimes it just doesn't go to plan. Take the example I have provided where the old knobset is a tubular style which has a spindle through the centre of the lock and engages into the latch. If you are replacing it with a cylindrical lock then you may have to drill out or enlarge the existing hole. Let me show you how.

Remove the two screws from the back of the lock and remove lock. Leave the latch in place.

Start drilling hole an a slight angle

Start drilling on slight angle with the hole saw centre drill inserted into the spindle hole. Drilling on the slight angle stablelises the drill. After cutting through, change the angle of the drill around slightly. Continue until completely drilled through.

You can now either remove the latch and continue to drill from the same side or you can leave the latch in and start drilling the other side. On timber doors, drill from both sides.

Now fit new latch

Now fit latch and knobset to follow. The front of the knobset has an adjustable rose to suit different door thicknesses. If you find the knob is hard to turn after tightening then you will most likely need to adjust the rose in more. Be careful not to wind in too far as this might allow the lock to slip of the latch.