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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?

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While 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 Dec 2 '11 at 18:11
    
At least the setback looks correct at 2 3/8 for a modern doorset –  HerrBag Mar 7 '13 at 14:30

5 Answers 5

up vote 17 down vote accepted

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.

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I tried this yesterday, and it works great. It's like a homemade door jig, using only the tools you already have. –  Jeremy Stein Jul 11 '12 at 13:20

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. :)

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These jigs will run you around $25-$30 and are conveniently located in the same aisle as the knobs. –  shufler Dec 2 '11 at 17:54
    
Or in the tool section. –  The Evil Greebo Dec 2 '11 at 18:04
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You can make yourself a similar jig with your new hole saw, some scrap wood and a couple of clamps... –  Ben Jackson Dec 2 '11 at 19:03
    
But then you wouldn't have another excuse to go to home depot!!! –  The Evil Greebo Dec 2 '11 at 20:35
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For 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 Jul 28 '12 at 4:56

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.

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Ok THIS technique will work w/o the jig - but its much slower. :) –  The Evil Greebo Dec 2 '11 at 16:47
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For most people, this is a one-time task. –  Chris Cudmore Dec 2 '11 at 16:48
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You say that as if that's a reason not to buy another tool... ;) –  The Evil Greebo Dec 2 '11 at 16:51
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Seriously though, these are the types of jobs that you would just rather not spend any extra cash if you can avoid it. –  Chris Cudmore Dec 2 '11 at 18:05
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Fair 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 Dec 2 '11 at 18:11

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

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.

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Nice idea with the dual hole saws. –  Chris Cudmore Dec 2 '11 at 17:06
    
OOOH. I need to get me one of those!!! –  The Evil Greebo Dec 2 '11 at 17:35
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wow, great answer ... I think you solved my similar problem –  Casey Jul 18 '12 at 20:44

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......

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Less about your experience and the product, more details of how the product/process works and I'll remove the down-vote. :) –  ShoeMaker Mar 16 '13 at 11:46
    
^ Agreed, SE sites are not a forum where we have discussions about products. –  Steven Mar 16 '13 at 13:59

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