What Size Hole Saw for a Doorknob and Deadbolt ?

So, you need to install a new doorknob or deadbolt and you’re not sure what size hole saw you’ll need to drill? Or perhaps you’re replacing an old rusted doorknob with a fresh-looking new one?

Either way, you’ll need to know the right size hole saw for your doorknob or deadbolt. Luckily, these sizes are pretty much standardized at 2 1/8” for both doorknobs and deadbolts for the primary hole.

In addition to the primary hole, you’ll also need to drill a second hole for the sliding bolt assembly. This is normally 1” in diameter.

Hole saws are the ideal tool for drilling a large diameter round bore hole with no imperfections. All you need is a decent power drill and a hole saw to get started punching holes into your new door.

Let’s take a look at the process of drilling bore holes for doorknobs and deadbolts, which hole saw sizes you’ll need, and what else you’ll need to get the job done.

Drilling Holes for Doorknobs – Guide

When it comes to drilling new holes for doorknobs, the key to success is proper preparation. Just like when you’re cutting lumber, you’ll want to measure twice and cut once.

Drilling Doorknob Hole

The first thing you’ll want to do is check the packaging of your doorknob to make sure you choose the right size hole saw. Most bore holes will be 2 1/8” for the primary hole, although there is some variety with deadbolts and older lock types.

You’ll also want to examine your door to ensure it’s the right thickness to accommodate a standard doorknob or deadbolt. Typical door thicknesses are between 1 3/8” and 1 3/4”, any thicker or narrower and you may run into problems.

Also, be sure to determine the right backset for your doorknob set. The backset is the measurement from the edge of the door to the center of the bore hole. It will be either 2 3/8″ or 2 3/4″, with 2 3/4″ being mostly for exterior doors. Some doorknob sets can be installed with either backset measurement and have a latch assembly that toggles between the two dimensions.

latch assembly for door knob
Latch assembly with both backset measurements.

Mark your hole location with the paper template that comes with the lock kit, or purchase a door lock installation kit that comes with a c-clamp to guide your hole saw through the door. Line up your hole saw carefully with the pilot bit directly in the middle of the template.

Drill through the door until you can see the pilot bit protruding out the other side. Then, flip over to the other side and complete the hole by drilling until the hole is complete. Switching sides halfway through the cut will prevent blowout and splintering, and keep the hole nice and clean.

Drilling Latch Hole

Now you’ve completed the primary hole to house the doorknob or deadbolt, but that’s only half of the job, you still need to create the hole for the sliding bolt to pass through.

For this task, you can use either a 1” hole saw, or a 1” spade bit. A hole saw will be a little more accurate and slow, and if you have a door lock installation kit, it probably comes with a 1” hole saw included.

latch hole
1-inch diameter latch hole.

Using either a clamp template or a paper template to mark the drilling location, line up your drill and drill perpendicular to the large diameter hole you created in the previous step.

Installing Faceplate

The faceplate is the flat metal plate that mounts to the edge of the door to protect against wear and tear. To install the faceplate you’ll need to create a mortise using a chisel or router.

Place the faceplate around the hole you just drilled on the door’s edge. Trace the outline with a pencil, which will form the perimeter of your mortise.

You can create the mortise using a hammer and chisel, or if you have a router it will make the task easier.

Then screw in the faceplate using the included screws.

fastening face plate
Fastening face plate.

At this point, the doorknob or deadbolt can be assembled and installed through the holes you just drilled.

With the lock assembled, there are still a few more important steps before you can use your lock. You’ll need to create a mortise for the strike plate, as well as drill another hole into the door jamb to accept the bolt.

Installing the Strike Plate

The strike plate is a flat metal plate with a hole inside it to accept the bolt. It installs directly opposite the deadbolt or doorknob and works to reinforce the lock from damage.

There is a minor difference between strike plates for deadbolts and doorknobs, which is the metal lip on the interior side of a doorknob strike plate. This lip is designed to make the door close smoothly when you shut it and requires a slightly different mortise shape than a deadbolt strike plate.

One thing to consider when installing a deadbolt is that a longer, beefed-up strike plate with extra mounting screw holes is a great way to secure your door from being kicked in.

To install the strike plate you’ll need to match the hole in the plate to the bolt inside the deadbolt. An easy way to do this is by covering the flat end of the bolt with marker or paint, and then extending the bolt all the way so it depresses into the door jamb.

This leaves a nice outline of where you’ll need to place the strike plate and create a 1/8” deep mortise.

Then test the fit of the strike plate using the included mounting screws (go with 2 ½” or longer screws for added security). Next, remove the strike plate so you can drill the hole to accept the bolt.

strike plate installed
Installed door knob strike plate.

Drill Bolt Hole

Finally, you’ll need to drill a hole in the door jamb to accept the bolt. Use a 1” hole saw or spade bit to drill a hole in the middle of the mortise you created in the previous step. You can use the same trick as before to mark the location of the bolt hole.

Once you finish the bolt hole, fasten the strike plate, close the door and test out your installation. The door should close smoothly with minimal effort and the bolt should pass into the door jamb without any snags.

If the lock isn’t operating smoothly you may need to do a little fine-tuning and repositioning until everything is working properly.

Denis Gardner

I've loved tinkering and fixing things for as long as I can remember. So, naturally, I gravitated towards DIY and home improvement when I bought my first home. Nowadays you can find me writing about my passions or messing around with my newest tool!

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