How do I drill a 2⅛ inch door knob hole over an existing 1½ inch hole?



I need to replace the door knob for this interior door:

Door with door knob hole

The door knobs I've found at the stores require a 2⅛ inch hole. Mine is only 1½:

Measuring 1½ door knob hole

Did door knobs used to be smaller? Is there some place I can find a replacement door knob that will fit my door?

If I need to modify the door to fit a modern door knob, will the new hole completely overlap the old? and can I reuse the latch hole?

Jeremy Stein

Posted 2011-12-02T16:15:38.947

Reputation: 654

The jigs made of plastic are only attached with 2 screws on the edge of doors. They will move if you aren't careful. The double hole saw method works best for my projects. – None – 2016-04-30T23:51:04.110

9While knobs in the store are typically pre-configured for larger holes, I was surprised recently to discover they often include instructions to fit them in smaller holes. It required removing a few pieces and flipping a couple things around when I did it recently, but check the instructions for the knob you plan to install and make sure this is necessary. – Scivitri – 2011-12-02T18:11:27.823

At least the setback looks correct at 2 3/8 for a modern doorset – HerrBag – 2013-03-07T14:30:55.127



i used a piece of plywood clamped to the door as an outer-guide. Cut a hole in the plywood, the right size (2 1/8) and then clamp it where you want the new hole in the door. Then using it as a guide on the outside of the hole saw, drill on through the door. voila. no additional tools required beyond the 2 1/8 hole saw, and well, a c-clamp which you should have.


Posted 2011-12-02T16:15:38.947

Reputation: 306

1I tried this yesterday, and it works great. It's like a homemade door jig, using only the tools you already have. – Jeremy Stein – 2012-07-11T13:20:06.563


Two other options. If you need to expand the hole with the exact same center, you can get a hole saw kit that uses an arbor with multiple attachable hole saws. Place the larger size hole saw with the smaller size inside of it, and tighten the arbor on both. The smaller hole saw acts as a guide in your existing hole.

enter image description here

For this to work the smaller hole saw must be the same or longer height, as depicted in the picture above. If they are the same length, the thickness of the base of the larger hole saw will cause it to protrude slightly. You can also use a washer to give it more depth as long as you can still secure the bit to the arbor.

The second option is similar to Chris's suggestion. Clamp a thin piece of plywood over the hole on the door, and drill through that. Pay special attention to keeping the drill level. The plywood keeps you from sliding all over the door. Just make sure you clamp it on well.


Posted 2011-12-02T16:15:38.947

Reputation: 38 597

This comment was from an anonymous user that tried to edit the answer: Used the hole set idea putting a 1.5" hole saw inside the 2.125" hole saw, on the same arbor.....also added a washer between the two saws to give better pilot on the inner saw. Worked beautifully. Thank you! – Ed Beal – 2016-05-24T19:43:44.777

7Nice idea with the dual hole saws. – Chris Cudmore – 2011-12-02T17:06:09.953

OOOH. I need to get me one of those!!! – The Evil Greebo – 2011-12-02T17:35:48.343

1wow, great answer ... I think you solved my similar problem – cmcginty – 2012-07-18T20:44:57.147


Yes, door knobs used to use smaller holes.

You probably can find a replacement, but if you want to use a modern door knob, yes you can reuse.

Get yourself one of these babies:
Irwin door-hole jig

It's a door knob jig - you can find them at the major box stores and they come with the appropriate drill bits. Align the jig with the existing latch hole, and then use the larger hole to enlarge the bore of the main hole.

DO NOT try to enlarge the hole w/o the jig. Your hole drill center bit won't have anything to bite into (since there's a hole there already) to hold it steady when the main cutting circle hits the wood and it'll slide all over the place.

This is a fantastic investment compared to buying a new door. :)

The Evil Greebo

Posted 2011-12-02T16:15:38.947

Reputation: 21 070

I have never had that problem. – The Evil Greebo – 2016-06-14T12:51:13.370

1These jigs will run you around $25-$30 and are conveniently located in the same aisle as the knobs. – shufler – 2011-12-02T17:54:46.007

Or in the tool section. – The Evil Greebo – 2011-12-02T18:04:55.697

15You can make yourself a similar jig with your new hole saw, some scrap wood and a couple of clamps... – Ben Jackson – 2011-12-02T19:03:04.110

But then you wouldn't have another excuse to go to home depot!!! – The Evil Greebo – 2011-12-02T20:35:38.920

I finally bought the same Jig. exactly for this situation. – shirlock homes – 2011-12-02T23:21:18.457

3For a contractor or landlord the added precision and durability of a commercial jig would make sense. For the typical homeowner that will do this once a decade making one from scrap wood is probably the way to go. – Brad Mace – 2012-07-28T04:56:30.540

I tried this and almost destroyed the door. The poor plastic jig in the picture is not strong or stiff enough to hold the hole saw in place - it depends on the centering bit for that. The other answer suggesting making a guide out of a piece of wood worked much better for me. If you have the plastic jig, you can use it to cut a piece of wood so that it is easy to line up correctly and use as that guide. – metamatt – 2015-06-19T17:25:39.753


If the new hole location completely encloses the old hole, then it's relatively easy.

With a 1.5" hole saw, cut a piece of 2x4 and plug the hole. You may need to sand or wrap it in paper to make it fit snuggly. Then you can use the 2 1/8 hole saw to cut the new hole.

If you need to move the location completely, then you need to plug the hole, leaving about 1/8 to 1/4" recesses on each side, and putty/plastic wood over it. Sand and paint.

You can usually buy a cheap set of 4-5 hole saw bits for under $20. That's sufficient for occasional use.

Chris Cudmore

Posted 2011-12-02T16:15:38.947

Reputation: 11 463

Ok THIS technique will work w/o the jig - but its much slower. :) – The Evil Greebo – 2011-12-02T16:47:26.723

2For most people, this is a one-time task. – Chris Cudmore – 2011-12-02T16:48:08.603

4You say that as if that's a reason not to buy another tool... ;) – The Evil Greebo – 2011-12-02T16:51:05.500

Well, you have to pick and choose. – Chris Cudmore – 2011-12-02T17:43:35.103

I deny that claim completely! – The Evil Greebo – 2011-12-02T17:45:52.353

4Seriously though, these are the types of jobs that you would just rather not spend any extra cash if you can avoid it. – Chris Cudmore – 2011-12-02T18:05:54.670

1Fair point - I end up doing a LOT of doors with my rentals but for a one time gig, a cheaper approach could be desirable. – The Evil Greebo – 2011-12-02T18:11:18.157


I was in exact same situation replacing a 1970 door lock got a name brand lock and the barrel was protruding while hitting back of knob hole.

Wondered same thing,
it's like my new lock was John Holmes wtf.

Anyways I went back to home Depot there was a $25 Cdn deadbolt Lock called Defiant there , I recall also using one last year at a friend's apetment it's pre configured for the smaller hole and adjusts by spining it to longer hole.

VIOLA no drilling or or Jig headache required.

DEFIANT brand $10-15 USd or $20-$25 Cdn Walmart, Home Depot and Lowes all sell it. Installed that and a pull handle on both sides, last year I simply drilled a hole for old liock above deadbolt which was in existing hole. That way I had a pull without buying anything extra. I may do that here and return gate pull.

Defiant Single Cylinder Stainless Steel Deadbolt DL61 at The Home Depot - Mobile

Also Google how to adjust the backseat and your brand of lock. enter image description here

Will Williams

Posted 2011-12-02T16:15:38.947

Reputation: 1


I did this today on a wood door using a Dremel with a sanding attachment on it.

First I outlined in pencil where the screws hit the door and sanded out that part, first on one side of the door, and then the other. Once the screws would go through, I traced a line where the door knob would be inserted into the door (this was on the lock side only.)

Since this doorknob only had semicircular pieces - top and bottom - that inserted into the door, I just reamed out the top and bottom of the existing hole until the doorknob would fit in. Not as elegant as using a hole bit, but this was the tool I had and it worked just fine. Took a bit longer, I'm sure, but it worked. (I think next time I'll buy a hole bit.)

Harriet Homeower

Posted 2011-12-02T16:15:38.947

Reputation: 1


As Chris said. If you are only doing one door, you can cut a plug, same thickness as the door, that you can glue into the existing hole, flush with the surfaces. Then mark the center of the old hole, or, the new backsets (latch) measurement, usually 1-3/8" or 1-3/4", but most are adjustable for either, from the edge of the door. Use the block for the pilot drill to center the hole saw and cut the new hole around it


Posted 2011-12-02T16:15:38.947

Reputation: 121


I did this today by using a Dewalt door lock installation jig. I bought this at Lowes. It cost more than the Irwin model but I bought the Dewalt because of the clamp on the jig. It was about $30 but I have several door knobs that are over 50 years old and need replacing. The Dewalt jig worked perfectly. Line up it up, clamp, and drill. It only took about 10 min. to drill and then mount the door knob. This tool is worth the money!

Now my wife want to replace more worn door knobs. I've already been back to Lowes to buy more......


Posted 2011-12-02T16:15:38.947

Reputation: 1

Less about your experience and the product, more details of how the product/process works and I'll remove the down-vote. :) – ShoeMaker – 2013-03-16T11:46:27.617

^ Agreed, SE sites are not a forum where we have discussions about products. – Steven – 2013-03-16T13:59:22.233