Milling Four Square Lumber

Introduction:

This tutorial assumes that you know how to safely operate your power tools. Always refer to the manufacturer instructions if you are unsure how to use your tools.

Any wood worker needs to take a board from the lumber yard or their local sawyer and make this board a uniform thickness, length and width. This board needs to have all four edges square to each other. This is referred to a milling a board four square and is a pre-requisite to any wood working project.

This is best accomplished by using a jointer, thickness planer, miter and circular saws and a table saw. In this example we will mill a board 30" x 4-1/2" x 5/8" with all for edges square to each other.

Step 1: Rough cut your stock
Rough cut your stock to 30-3/4" x 4-3/4" and maintain the same overall thickness. Start by selecting a piece of stock larger then your finished size (obviously) and use a framing square to square off one end of the board. Be sure the end isn't checked (cracked) and if it is square the board off just beyond where the cracks end.

Make the cut using a circular saw being careful to make a fairly square cut. Now measure 30-3/4", the rough length, and square off the board using your framing square. and make the second cut the same way you made the first. Be careful to cut on the waste side of the line.

Step 2: Rip to rough width
The table saw is the best tool for this cut. Set the rip fence so it is 4-3/4" from the blade and set the height of the blade so the gullet of the teeth are the same height as the stock. Following the directions included with your table saw start the blade and make the cut, being sure to use a push stick.

Step 3: Truing one face
Now that your piece of stock is the rough size needed it is time to true up one face. This is best accomplished with the jointer.

As always with the jointer it is advisable now to take more than 1/16" per pass. Taking more wood per pass will overwork the machine and give results that are less than optimal.

Analyze the board to determine the direction of the grain and whether there is cupping. It is best to place the cupped face down since it will site better on the jointer table. Run the board through for a couple of passes until you have a uniform face free of voids and dips.

Step 4: Truing the second face
The thickness planer is by far the best tool to accomplish this. On the jointer it is simple to get the second face true but it is quite difficult to get it parallel to the first.

The thickness planer guides the board and makes the second face exactly parallel to the first. Once the second face is true and parallel to the first continue to plane the board until it reaches the finished thickness, in this case 5/8". Remember to feed the stock with the grain to ensure a smooth clean cut.

Step 5: Square one edge
Back to the jointer for this step. Set the jointer fence so it is exactly 90 degrees to the table and be sure the cutting depth is set to 1/16". Determine the direction of the grain and place on face against the jointer fence and make a pass through the cutter applying steady pressure against the fence.

Once you are satisfied that the edge and face are square to each other mark the edge for reference.

Step 6: Square the other edge
Now that you have one edge prepared it is back to the table saw to rip the board to width. Set the fence 4-9/16" (1/16" larger then needed). With the marked edge against the table saw fence rip the board. Now return to the jointer and make one final pass, milling the new sawn edge. Be sure that the jointer is set to 1/16".

Step 7: Squaing the ends
I prefer to use a table saw to square the end and cut the board to length although a table saw with a miter gauge will work as well. Check that your miter saw is cutting a true 90 degrees and when you are sure it is trim one end of the board, taking as little off as possible. Now measure the finished width of 30" and make the cut taking care to cut on the waste side of the line.

Conclusion:
You should now have a board that is 30" x 4-1/2 " x 5/8" with all four sides square to one another.

There are a number of methods that will work for milling a board square, however I have always had good luck using this method.