Resawing A Sawn Hole With A Hole Saw

Say that 10 times fast.

Here’s the problem: The oak high-tank for the toilet was originally intended for an 1.25-inch flush tube. The flush tube is the long tube that connects the tank to the bowl. I wanted to go to an inch and a half flush tube because I would save about $90 in parts, but also because I have an inch and a half flush tube on the upstairs high-tank toilet, and I wanted them to sort of look the same. Also, it just so happens that DEA Bath is sold out of the smaller flush tubes, so even if I wanted it I couldn’t get it.

So now I have to an existing hole on the bottom of the oak tank and I need to enlarge it. If you’ve never used a hole saw they are easy to use to make new holes in existing wood, but it can be tricky to widen an existing hole. Here’s a picture of a hole saw.



You can see it has a drill bit in the center. The drill bit centers the saw and keeps it from dancing around on the wood while you start the hole. The drill bit hits the wood first and sort of guides the hole saw down on to the wood. When you are enlarging an existing hole there is nothing there for the drill bit to drill in to.

This is probably one of those things where I think I’m very clever for coming up with a solution and a lot of people are out there saying to themselves, “Well, of course that’s how you do it! How else would you?” Be that as it may, I can’t be the only person who has struggled with this, so I’ll post my solution here so maybe some day it will help somebody else.


This is what I started with. The hole in the center is 2-inches wide and I need to go to 2.5-inches


This is the flush valve. Ideally the threaded part would fit in the hole. As you can see, it won’t. If I just put the hole saw on there and tried to drill it would be a bitch to keep in centered over the existing hole. Most likely the new hole would be off center and finish would be severely scratched up.


What I did was take a scrap of ¾-inch plywood and cut a 2.5-inch hole through it using the hole saw. I then centered that hole in the plywood over the hole in the tank and clamped the plywood to the tank.


The hole in the plywood acted as a guide and kept the hole saw centered over the hole. The results were a nice clean and well centered hole.


And there you have it, the new flush valve installed. I hope this helps somebody down the road someday. Now the only question is, how much wood could a woodchuck chuck if a woodchuck could chuck wood. I'm just curious.