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.

[MitchellMc]

Welcome to the Bunnings Workshop community @GeorgeP. It's sensational to have you join us and many thanks for your question about door latch installation.
 

You can use a Door Lock Installation Kit to increase the width and depth of your latch hole. It would be advisable to use one which includes a guide like the Craftright Door Lock And Deadbolt Installation Kit. Since you already have a hole, the guide will allow you to drill in the correct position without the holesaw skipping around on the surface because the drillbit has nothing to bite into.

Please let me know if you have any questions or need further assistance.

Mitchell

[GeorgeP]

Thank you for your advice, that looks to be a good solution. Could you tell me would I have to buy separately a suitable centre drill for the hole saw, will the 25mm holesaw allow deepening the present hole and (probably not important can) you preset the depth for this.  

[MitchellMc]

The Craftright Door Lock And Deadbolt Installation Kit comes with a centre drillbit @GeorgeP. You can't preset any depth on it. The 25mm hole saw is approximately 40mm long, so you'll be able to drill to a depth of around 50-60mm. On a door that hasn't had a handle attached before, the remainder of the depth you require to install the latch is achieved by drilling a 57mm wide hole through the face of the door. In your case, that's going to be a problem as you already have a handle hole and won't want to move it. You might need to grab an Irwin 25mm Speedbor Spade Drill Bit to send down your new drilled 25mm hole to clear out the end to accept the new latches length.

You're kind of a bit caught as you really need that hole saw and guide to enlarge a preexisting hole. You will have real trouble using a 25mm spade bit to enlarge a 21mm hole by itself as it will just skip around on the surface. The depth you drill to is not particularly important as the latch is fixed by its plate on the edge of the door. If you drill slightly deeper than 82mm, it's no problem. However, you can mark the spade bit shank with some tape to check your depth.

Mitchell

[GeorgeP]

Thank you for the reply Mitchell.

I think I have a problem - just hope there is a solution. I measured everything again and the distance between the edge of the door to the edge of the large hole from side to side for the handle installation is 50mm, so the 25 mm hole saw will take me to there ,then I have space across the large hole is 23mm  but then the hole for the latch goes further in for some 16mm. The entry to this is curved along the wall of the 23 mm handle hole and to make matters worse this part slants to one side so there is only a few mm of wood on this side - see pics. I think even  if a hole saw that will go 80mm deep exists I may damage one side of the door, even worse with an unstable spade drill. Would you have any suggestions?

[MitchellMc]

Hi @GeorgeP,

Have you tried inserting the new latch at all? You mention that the new latch is only 2mm longer than the old one. I doubt whoever installed the old latch could drill a hole at the exact required depth. They likely oversized it slightly, and your new latch might just fit.

It's unfortunate the hole skews off at an angle. It doesn't give you much room to work there. You could give drilling the hole a go, and hopefully, if you penetrate the surface of the door, the damage can be repaired. Alternatively, you could always move the position of the handle up or down the door.

Let me mention a few of our knowledgeable members @TedBear, @Remarka6le and @Noyade to see if they had any thoughts.

Mitchell

[Remarka6le]

Two things come to mind: If you had an arbor extension, you could reach depths to (and deeper) than 80mm should you need it. But if I were only needing to go 2mm, I'd be using a small chisel and hammer to get some precise cuts, as we've done with all our in the past.

[EricL]

Hello @GeorgeP 

Have you thought about filling in the old holes and relocating the new door handle and latch to a new location on the door? Perhaps just a little bit higher from its original location. In that manner, you won't have to modify the existing holes so much and just make new ones.

If you need further assistance, please let us know.

Eric

[TedBear]

Hi @GeorgeP I am having trouble picturing the issue here....   you mention a new door handle, and also having a depth issue, yet I am picturing the usual door handle set-up that goes right through the door, with a handle on both sides.  Is that not what you are dealing with here?

I am wondering if the depth issue you refer to is that of the bolt that slides into the door frame...  is that what it is that needs to be 80mm deep.

If so, then hammer and chisel may be best as suggested.

If the hole in the door side needs to be made a little wider for the new unit, I would be using a large round file or the curved side of a wood rasp to open that small amount up quickly.  The surrounds for the handle should cover up any slight "out-of roundness".

But, as I said, I may not be picturing the situation correctly.....

[GeorgeP]

Thank you all for your suggestions, I  think I will have to try the chisel and hammer. It may be safer than a poorly controlled power tool especially  as the deep 16mm hole is skewed off centre, I think I will be able to enlarge the hole walls to take the corners of the latch (the profile of this is 15x20mm and 80mm long) and if necessary (when I can try the latch in to the bottom) I guess I can chip away a bit of the bottom to deepen it by 2mm

I am interested in your mention of an arbor extension - I do not know about these could I have some information, could it work with the Craftright guide and the 25mm hole saw or would something else be needed? This is because I have a second door whose old latch ( same brand) has failed) this one did not jam it just died open. And I bought two replacement handles .

Thank you Eric for your suggestion but I think  filling in everything would be beyond by ability, plus the door is in a metal door frame which would also have to be modified.