Every woodworker should know how to mill their own boards
If you’ve ever bought two-by-fours from a big-box store, you know that not all lumber can be straightened or flat. Wood is very hard but can bend, bow, or bend when it dries or is exposed. It can be difficult to work with warped wood: precision cuts will be more challenging and joints will be less strong.
Before you can start a project using wood that you have just purchased, you will need to mill it. This is woodworker talk for trimming a board to a three-dimensional rectangle (aka cuboid) or rectangular prism. This involves flattening both faces, cutting the edges at 90 degrees to those faces and parallel to one another, and trimming each end to your desired length at a right angle to the freshly straightened edges. Everything I built was easier to put together once I learned how to properly mill lumber. It is time-consuming at first, but it is well worth it in end.
One thing to remember is that the steps below will show you how to perfectly mill wood with modern power tools. You don’t need to be exact with your wood, especially if you aren’t gluing multiple pieces together complex joining techniques .. My current project is a pair floating shelves that need to be square and flat. To get the wood flat enough, I used a handplane to flatten it. So before you spend hours getting within 1/32nd of an inch, think about the level of precision you actually need. Sometimes, it is enough.
You can also mill wooden with only hand tools , but that takes time and practice.
Warning: DIY projects can be dangerous, even for the most experienced makers. Make sure you have all the safety gear necessary and know how to use it properly before you start this project or any other one on our site. Safety glasses, a face mask and/or ear protection are all essential. You must be able to safely and correctly use power tools. Do not attempt this project if you don’t know how to use them correctly or are unsure.
- Time: 1 to 4 hours
- Cost: None
- Difficulty: moderate
- Moisture meter
- Table saw
- Push block
- Crosscut sled (or miter saw)
- (Optional) jointer sled for the table saw
- (Optional) flattening sled for the planer
- (Optional) hand plane
1. Properly acclimate, dry, then store your wood. Wet wood warps. Wood that is dried warps. Wood that is exposed to changing environments warps. It doesn’t matter how square your wood is, if it hasn’t been properly dried and stored. It will warp once again.
When you bring your wood home, make sure to test for moisture. Your planks should have a minimum of 9 percent moisture. If they are too wet, let them dry out. You should allow the boards to sit in your shop for at most a few days to adjust their environment to the temperature and humidity.
Don’t stack boards so that they dry on top of each other. This can trap moisture between them, which could cause additional warping or cracking. To ensure proper ventilation, slide small pieces of wood called stickers between each board. This will allow planks to dry more evenly.
To make my stickers I cut strips approximately half-inch wide from any scrap wood I had lying around.
2. Flatten one face. After a piece is dry, flatten one side. There are several ways to do this. A jointer is the best tool for this task. Slide the board over the rotating cutter head and along the tool’s bed. Push blocks are the best choice as you don’t want to touch the blades. It may take several passes to flatten the face.
If you don’t own a jointer, a planer can flatten wood. However, you’ll need to build a sled to do it. A planer’s cuts are not based on a flat surface. This is why you can’t flatten a board without a sled. Instead, the planer will follow contours of the bottom of whatever material you feed it. If your board is bent, the planer will trim the top of the piece of wood to correct the problem. You can force the planer’s attention to the milled surface by using a sled. This will leave a flat cut.
- Pro tip: To help yourself see when you’re done, scribble all over the face you’re working with a pencil. You’ll be able to see that the face is flat when all pencil markings have disappeared.
- Note: For those without a planer or jointer, you can build a router sled to flatten the faces of your boards, but that’s more labor intensive, particularly if you’re milling a lot of wood.
3. Join one edge. Now, that one side is flat, it’s time for trimming an edge. This is where the goal is to make sure that the edge is straight and parallel to the flattened face. A jointer is the best tool for this task. First, choose which edge you want to flatten. I usually choose the one closest to flat. If they are both wonky, I will cut the one that rides more securely on my jointer.
Place your board on the jointer-infeed table with the selected edge down and the flattened face against the fence. Trim the edge by pushing the board over the cutter head. This will likely take several passes. Once you are done, the edge should be straight and at an angle to your face.
- Pro tip: Use a pencil to mark the edge and face you have flattened, drawing arrows that point to the 90-degree corner so you don’t lose track of what you’ve done.
- Note: If you don’t have a jointer for this step, you can edge joint a board with a table saw.
4. Flatten the second side. If you have a planer this is easy. Simply flatten the board and run it through the machine. You can see how much wood has been flattened by scribbling on the rough side of your board.
The planer is the best tool to do this job. It cuts parallel to the bottom of the board, so you get uniform thickness. The jointer is not capable of cutting parallel to top face. The board will most likely form a taper from the front to the back if you try. This defeats the purpose of milling.
If you don’t own a planer, there may be other ways to flatten the face. You can use a router, which is also an option in step 2. The second option is to use a router sled, which was also an option for step 2.
5. The remaining edge should be cut. You now have two parallel faces and one edge that is at a 90-degree angle to both. Next, trim the remaining edge of your table saw. If you know the exact width of the board you want, adjust the distance between the blade and the fence on your table saw. If you don’t know the final width of the board, set your fence to trim a small portion of that edge. You can reduce waste and make the board more flexible for future projects by using a small amount of wood.
[Related: Tune up your table saw the right way]
Run the board through the saw, with one side down and the jointed edge against fence. This will create a cut parallel with the edge. It is also perpendicular for both faces.
- Pro tip: Anytime you use your table saw, check the angle of the blade with a digital angle finder. On some projects, like cutting boards, there’s a noticeable difference between 89.8 and 90 degrees.
6. Trim the ends to your desired length. You can trim the ends with either a mitersaw or the table saw’s crosscut sled. I prefer the latter because it allows me to have more control with my table saw. Additionally, clutter builds up near my mitersaw and I have to pick them up every time I use it, whereas my tablesaw is usually clean.
Place one of the edges against your fence (if you are using a table saw), or the fence built into your saw (if using a mitersaw). Then, trim enough wood so that the first end is flat. Flip the board over and cut the desired length. If you aren’t sure what you want, you can simply cut enough to flatten the other end.
- Pro tip: I try to keep the same edge against the fence for both cuts, for consistency’s sake, but if you’ve properly milled the lumber to this step, it shouldn’t matter which edge you use.
Now your board is perfectly square in every dimension. This opens up a whole new world for woodworking. Get out there and start building.
I’m a journalist who specializes in investigative reporting and writing. I have written for the New York Times and other publications.