Call me Dr Doorknob
I guess the builder let an apprentice put the door handles on our house. Four of them, the holes are off centre and one side of the handle assembly is unsupported and collapsing into it.
If the hole were correctly positioned there would be no problem. If the hole were smaller, the margin for error would have been larger and the positioning wouldn’t have been a problem.
So how do you make a hole smaller?
It was cut with a hole saw. I have one of those, and it didn’t take long to find a blade of the (standard) size used to cut the hole.
I bought some timber the same thickness as a standard internal door (38mm) and cut a hole in it. After removing the door handle/latch assembly, I found the resultant plug fit nicely into the hole. I glued it in place using two-pack epoxy, which was a mistake but not a disaster.
Cutting the plug left a centring hole in it, and this was very handy for positioning a 22mm barrel auger to cut a much smaller hole for the handle crossbars.
A 25mm auger extended the existing lock barrel hole through the plug.
I screwed the thread barrels onto one of the handle assemblies and used a crossbar to position it correctly. Tapping the handle smartly with a rubber mallet marked the plug with the positions for the 5mm thread barrel courses. Inserting the handle assembly allowed me to use the lock pin hole in the handle assembly to mark the position for the 5mm lock pin course.
I used a drill guide to help me keep the drill perpendicular to the door, and drilled right through for the thread barrel courses, and halfway for the lock pin. The whole thing needed assembly several times to check course positioning, with adjustments using a routing bit, and then it was a simple matter of assembly.
The first one was a mess. Positioning was a bit rough, and crud stuck to the job as well as little hard strands of epoxy. But all the defects are presentational: sandpaper and paint are all that’s required to perfect the work.
I learn from my mistakes, and the second one went far more smoothly. Instead of epoxy I used PVC wood glue, which takes much longer to hold-set but cleans off with a damp cloth.
The door material through which the lock barrel hole was cut was soft and porous, probably some sort of low density fibreboard (aka shitboard). I smeared the inside of the hole with PVC glue. The porous material absorbed quite a lot of glue. My purpose in doing this was to improve the integrity of the material while I was using it as a guide, and this proved very successful.
By the third try I learnt to bore the lock barrel hole before the crossbar hole, and to bore the crossbar hole as inwards from both sides into the resultant cavity, resulting in a better finish. In addition, the positioning error (for the original oversize hole) was less severe for the second, third and fourth jobs, and no plug timber is visible past the outer handle assembly sleeve. As a result, only the first job requires cosmetic touch-up.