How to enlarge a hole in a door for a new door latch?

[GeorgeP]

I have to replace a door handle - the old latch mechanism is worn out and jams. It is  over 20 yrs old and not available anymore, but the company advised a suitable replacement.

However the existing latch hole is not big enough for the new latch. It is about 21mm diameter , the new latch needs 23mm. Th new latch is also about 2mm longer than the old putting them side by side, the hole would have to be at least 80mm deep, 82mm would be safer.

Is there a drill attachment or a tool to do this - I would be very grateful for any advice.

[Remarka6le]

Hey George, glad I could help  

Regarding the arbor extension, from memory the sizes are pretty universal so they should be compatible, but I would just ask a member in the tools section at Bunnings to confirm. I bought a bunch of different ones for different projects last year, they save so much time and effort. 

[GeorgeP]

Hello again,

I have had no luck searching for arbor extensions and how to use them  in Bunnings or on the net. The best I got is "Extensions - Longer arbor extensions will extend the reach of your hole saw to give you a deeper hole."  from an UK tools site. Which sounds like what I need - to extend a 25 mm hole saw to go to 80 - 82 mm depth. I am in the high risk group with Covid so reluctant to go searching in a store for face to face advice.  I hope to get some more advice here - what I need to buy and tips how to use. 

[MitchellMc]

You'd likely need to get an extended arbor like this Sutton Tools 1 / 2" HSS Holesaw Arbor @GeorgeP. There are arbor extensions out there, but I'm not familiar with any. I can't be sure if the arbor fits the Craftright kit, but it will fit a Sutton Tools 25mm TCT Multi-Purpose Seamless Holesaw.

We are just in a bit of a pickle since you are trying to adjust an existing cutout. The 25mm hole saw usually only needs to clear the edge of the door. The larger 57mm bit is the one that provides the additional room for the latch section to slide into. 

Mitchell

[EricL]

Hello @GeorgeP 

I suggest looking back into my colleague @MitchellMc's first suggestion about using an Irwin 25mm Speedbor Spade Drill Bit. In order for you to use this tool without jumping at the start of the old hole, you'll need to make a timber guide. The timber guide will hold the spade bit steady as it creates a new channel in the existing hole. This will also serve as an opportunity to correct the direction of the hole.  My number one tip is to make sure that the hole in the timber guide is dead centre to the old hole in your door. I've placed a sketch below for you to get an idea of how to set it up. If you have any questions about the guide, please don't hesitate to post them.

If you need further assistance, please let us know.    

Eric

Make sure the holes are centred.