Years ago the standard size for a cross bore was 1 ½” in diameter.  In order to include baffles and some other features the standard has changed to 2 1/8” in the last few years.  If you are replacing an older lock with a newer one, that can be a problem.  There are also cases where you might want to change the backset from 2 3/8” to 2 ¾” or vice versa.  Making either one of those changes can be problematic if you don’t have an installation jig and those jigs typically have a price tag of hundreds of dollars.

There is a simpler solution that will typically be good for one or two uses before you need to make a new one.  The tools you will need are:

• A drill
• A hole saw with the correct diameter
• Two C-clamps with 3” clearance (or more if your door is thicker than 1 ¾”
• Two pieces of ¼” plywood about 6” square

The first step is to measure from one edge of one of the plywood sheets to the center of the backset you want to put into the door.  Then use the hole saw to cut a hole in the plywood at that backset.  Clamp the plywood sheet to the door in the proper location using the two C-clamps and the undrilled plywood to avoid damaging the door.

The next step is to remove the lead bit from the hole saw.  Then place the hole saw into the hole in the plywood and carefully start the drill and push the saw toward the door.  Be careful to not have the saw touching the door yet when you start the drill as it could bite too deeply into the door and possibly cause damage to the door, or to you, if you don’t have a firm grip on the drill.

As you drill through the door the hole saw will encounter the other sheet of plywood and having it there will prevent the saw from tearing the surface finish of the door when it breaks through.  If your door has a grainy surface you may want to use the added precaution of covering that surface with masking tape as well to prevent tearing when the saw breaks through.  If you tape the door, always remove the tape after drilling by pulling it toward the hole, never away from the hole.

To use the template on another door, just remember to use an undrilled area of that inside sheet of plywood.