Looking for a key in knob entrance door set for 40mm hole

filthy

House I just moved into has a workshop door with its door knob removed by the previous owner. The door has a 40mm bore hole, 32mm thick and 60mm backset. 

I'm looking for a double cylinder key in knob door handle set but everything I've found needs a 54mm bore hole.

Is there one to fit a 40mm hole? I don't want to drill out to 54mm I'm worried I won't get it centred.

EricL

Hello @filthy

I understand your hesitancy in drilling a bigger hole in your door. But there is a safe way to do it. I suggest getting a piece of offcut timber around 125mm x 300mm x 20mm. Draw a 60mm line from the edge of the timber and mark it with a pencil. Follow it up with another line at a distance of 25mm. Find the centre of the timer piece and draw a guideline. Where the second guideline meets the centre line is where you need to position your hole saw bit. Once you've cut the hole follow the directions I've laid out in the images below.

Once you've cut the hole bigger you'll now be able to put any of the new door knob assemblies on your door. Please have a look at the sketches and tell me what you think. Please note that the timber guide needs to be clamped to the door. Although you do have the option of fixing it with screws, it adds more work as you'll need to repair the holes in the door.

If you have any other questions we can help with, please let us know.

Eric