Hole Saw Trick for Enlarging an Existing Hole
A hole saw makes it easy to drill large holes in wood. But what happens when you need to enlarge a hole that's already been drilled?
Normally, the pilot bit keeps the hole saw centered as it cuts. Once a hole has been drilled, however, there's no material left in the center for the pilot bit to engage.
I ran into this problem recently when I needed to make an existing hole larger. Without a drill press to help guide the cut, I needed another way to keep the hole saw centered.
The solution was surprisingly simple: Connect two hole saws together and let the smaller one guide the larger one.
Use a Smaller Hole Saw as a Guide
The trick is to use two hole saws of different diameters.
The smaller hole saw should match the diameter of the existing hole. The larger hole saw should match the new diameter you want to cut.
By connecting the two saws on the same centerline, the smaller saw fits inside the existing hole and helps guide the larger saw as it begins cutting.
This eliminates the need for a conventional pilot bit to locate the center.
Connect the Two Hole Saws
My hole saws use a 1⁄4" pilot bit that's secured with a set screw.
To make the setup, I removed the pilot bits from both hole saws and replaced them with a short length of 1⁄4" steel rod.
The rod connects the two saws and keeps them aligned, as shown in the drawing.
With the smaller saw positioned to guide the cut, the larger saw can follow the same centerline and enlarge the opening.
The result is a centered hole without having to lay out and cut a new opening from scratch.
WOODSMITH TIP: Check Your Hole Saw Setup. This arrangement depends on the design of the hole saw arbors and their set screws. Not all hole saws can be connected this way.
Make sure the components are securely retained and compatible with the drilling setup. An improvised connection that isn't designed to transmit drilling torque can come loose or bind. A manufacturer-approved hole-enlarging arbor or a securely clamped guide template is a safer alternative when compatibility is uncertain.
An Easy Solution for Oversized Holes
Whether you're modifying a shop project or correcting an opening that's too small, enlarging an existing hole can be frustrating when the pilot bit has nothing to guide it.
This two-hole-saw arrangement offers a practical solution when you have compatible equipment. The smaller saw provides the reference, allowing the larger saw to follow the existing hole.
It's a handy trick to know the next time you need to make a hole larger without starting over.
More Woodworking Tips & Tricks
Some of the most useful woodworking accessories are also the simplest. From shop-made finishing aids and workholding solutions to handy jigs and time-saving techniques, a few small improvements can make a big difference.
Discover more practical Woodsmith woodworking tips and tricks to make your time in the shop easier and more productive.
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