Enlarging an existing hole

[Tom M King]

Not exactly woodworking, but might prove to be useful.

In changing all the door locks in a rental house, I ran into an unusual situation, which is not unusual. There is a half bath in the kitchen. It had an exterior lock in the door with the key nowhere to be found. I was getting ready to install a normal privacy interior lock in it. When I took the old lock out, which was different than any I've ever seen, the lockset hole in the door was 1-3/4". The new ones call for the standard 2-1/8" hole.


My Holesaw toolbox contains years of accumulation of different sizes of holesaws, and different types of arbors that aren't compatible with all holesaws. Some have different sizes of threaded holes. There are also multiple different types of the two-pin types of arbors.


One of the old two pin arbors had a screw shank that would fit a 1-3/4" holesaw, and I found a 2-1/8" that had a larger threaded hole in it, but would fit on the pins. I seated the 2-1/8" on the pins, found a few washers to go over the threaded shank for spacers, and screwed the 1/3/4" holesaw onto the threaded shank.
It took longer to type this out than it did to find the parts, and enlarge the hole.
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Now I don't have to worry about some child locking themselves into that bathroom, and we can't open the door.

[Walter Plummer]

If you do a lot of holesaw work a good accessory to have is an "OOPS" arbor. https://www.amazon.com/Starrett-KA19-N-Oops-Arbor-Enlargement/dp/B01HOLS2WU. I like your solution also.

[Tom M King]

Thanks Walter, I hadn't seen that one, but just ordered one. I wouldn't say that I do a Lot of holesaw work, but they do get used every few years.

[Tom M King]

When I ordered that one, this one popped up too, so I ordered one of these. You never know what combination you might need.

https://www.amazon.com/Bosch-HE1-2-Piece-Hole-Enlarger/dp/B000WA7A56/ref=pd_bxgy_2/132-6116444-9449609?pd_rd_w=u042g&pf_rd_p=6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_r=VCKJ3RKGMD86AQ7S3K1B&pd_rd_r=ea2c3241-07ef-4233-89ca-4036b5047a42&pd_rd_wg=YnCBt&pd_rd_i=B000WA7A56&psc=1

[Bill Dufour]

Starrett had good prices on top quality saw blades for wood and metal. Very competitive pricing for quality goods. This still surprises me compared to their prices for precision measuring gear.
Bill D

[Maurice Mcmurry]

Thats very clever!! I do that with a template that I clamp to the door. It is just a board with a 2 1/8 hole drilled at 1 3/8 and 1 3/4 backset. With the template you can correct an incorrect backset as well. I shared my safety tip for hole saws in a bit brace thread... I use my SDS drill with a chuck adaptor for hole-saws. The clutch helps prevent a jamb from twisting the drill out of your hands.

[Doug Garson]

Haven't tried this but I think it should work. If you have a hole saw that matches the existing hole, drill a disc in a scrap piece of wood, wrap it with painters tape until it fits snuggly in the hole, then drill with the larger hole saw using the hole in the center of the scrap piece to center the saw. Nothing to buy assuming you have the smaller hole saw.

[Jerome Stanek]

You can get a lockset jig from the big box stores I have a PC set that I used a lot when I was installing doors

[Tom M King]

Box stores are a half hour one way from here. Maybe one of the plastic ones would have worked, but I just used what I had here. I have one of the Kwikset 138 installation kits, but the jig is made from metal, and I didn't have any blue tape here to put on the door to keep from scratching it up. Those holesaw adapters might come in good sometime in the future. I'm out in the country, and try to avoid unnecessary trips that end up killing half a day for some small thing.

[Rick Potter]

I have the same problem, except the small offshore door set is on a steel gate. It has a square of sheet steel where the knob fits, that needs to be enlarged a bit on both sides of the gate. I think the gate guy must have gotten the cheapest knobs he could, at HF.

Any thoughts? Would a bimetal hole saw work in a stacked configuration as above? I am also wondering about a wood pattern using a metal burr with router bit bearing on it. Gotta do two gates (4 sides).

[Phil Mueller]

Clever solution, Tom. I think I’ve had to do this twice in my lifetime. I used the plastic guide thing sold at big box stores once, and a scrap piece of wood as a template the other time. Both worked, but if like you, it was a more frequent need, the “oops” thing looks like a great way to go.

[Michael Fink]

If you do a lot of holesaw work a good accessory to have is an "OOPS" arbor. https://www.amazon.com/Starrett-KA19-N-Oops-Arbor-Enlargement/dp/B01HOLS2WU. I like your solution also.

That's a great idea! Learned (and bought) something new today. Had this problem plenty of times, this is an obviously good way to deal with it. Thank you!

[Tom M King]

Rick, the stacked hole saws will work, but you will probably have a hard time getting the leftover metal out from between the two hole saws. Hopefully, you have a big spade handled drill because a cordless one might be a bit dangerous to your wrists.

[Rick Potter]

Thanks Tom,

I have an old electric drill with a side handle augmented by a chunk of EMT. Never tried to cut metal with a hole saw, but there is always a first time.

Thanks for the warning.

[Maurice Mcmurry]

Another plug for using a drill with a clutch for hole saws and big bits. A co worker left the job on a stretcher bound for the hospital after getting whacked, tangled, and flipped to the ground by the pipe handle of a Milwaukee Hole Hawg. He was using a Schalage door boring rig with a 2 1/8 auger bit.

I see several of the old Schlage jigs on eBay. Interestingly there is a new version... the "Killer Jig" by Pro Lock

[Tom M King]

I just went to ebay to look at those Schlage jigs. The Kwikset 138 also holds the drill bit shank, so there is probably less chance of the bit getting in a bind. I don't remember ever having a bit grab while using it, but I have never used it to enlarge a lock hole. This particular case here is the only time I've ever needed to enlarge a lock hole. I had never seen a 1-3/4" lock hole before.

[Maurice Mcmurry]

An enjoyable thread and very much a "Woodworking" task. The stacked saws = clever!
There is an interesting genealogy of doorknob and lockset types. I still get to install old rectangular mortise locks from time to time.