All of our Dexter Locks do require a 2 1/8″ (54mm) bore. However, I have successfully re-bored existing smaller holes to the required 2 1/8″ size.
- 2 1/8″ hole saw. You can get a hole saw for your drill from one of the big box hardware stores for about $15.
- Scrap 1 x 4 or other lumber
Next, clamp a scrap piece of wood to the front and back of your door so that it covers the holes, but be sure you can still see the center lines.
Actually I have found that it’s even easier to mark perpendicular center lines on my scrap pieces of wood first, and then clamp the wood in place after lining up the lines on the door with the lines on the scrap wood. This keeps me from having to try and draw on the scrap wood while it’s on the door.
Finally I bore the new hole through both pieces of wood and the door at the same time. The back piece of scrap wood is not completely necessary, but it keeps the back side of the door from splintering when the hole saw punches through.
On my hole saw I can change out the shorter drill bit that came with it to a longer standard length drill bit. That really helps me keep the hole saw level as the longer drill bit grabs into the scrap piece of wood on the back side.
There are jigs that you can buy at the hardware store to do this too. The problem I have found with them is they are not thick enough to keep the hole saw straight when I start drilling, and they have not been of very high quality plastic so they were pretty flimsy. I am sure you could buy a more expensive jig and it would do the job, but depending on how many times you will use it and how much your new deadbolt locks (or any other lock I guess) will cost in the first place it might not be worth the money.