I need to cut three 2x4 pieces (about 2 feet) and their size should be exactly identical. What would be a good way for doing that with a circular saw? The articles I found recommend using a miter saw and a stop block but I have only a circular saw. I am thinking of clamping three lumbers, making the ends of them flush and cutting them at once. But, I am wondering if there is any other better way.
What you just described (cutting multiple pieces at the same time) is in the construction field referred to as "gang cutting". And, yes, if your only power tool is a circular saw, than to get the most precise and exact lengths, cut them in a gang cut. What you should first do is make an initial gang cut at the bottom so as to square the ends. Than measure and mark the length. After they are clamped strike a line with a square across all pieces. If you have a steady hand slowly begin the cut being sure to keep the saw blade to the waste side of the line. Or clamp a guide fence down so that when the saws base plate edge rides along it the blade is at the appropriate mark (usually 3- 3 1/2 inches from inside blade edge to outside plate edge).
Cut one. Use that to make lines on the others.
That's what I do. Done it many times. Just cut real slow. And make sure the edge of the blade is lined up on the correct side of the line you draw (use a fine pen).
To get it right, draw a test line and cut it so you can see how your saw kerf runs.
Use one of these to draw lines on the wood perpendicular to the edge.
Obviously I'm a bit late to help you out, but you can build a jig for a circular saw to cut the same length. Probably overkill for 3 pieces but if you're cutting 10 or more, it's a good way to go. It sounds like a lot of work listed out like this, but really it's maybe 5 minutes of setup time.
- Start with a scrap piece of plywood. Since most circ-saws are right-handed, put a stop-block on the left side of the plywood.
- Screw two 2x4s to it, parallel to each other and far enough apart to allow the size of whatever you need to cut to slide between + 1/8 inch, with their left ends touching the stop block.
- Measure from the stop block to your desired length and make a mark, and square it across the two 2x4s. If you're cutting something wider than a 2x4, cut a strip of plywood long enough to cross the two 2x4s and maybe 3 inches wide: this will allow the saw to be supported across the length of the cut.
- Set your saw depth to 1/8 deeper than either the 2x4 or the 2x4 + plywood if you used it in the last step, so we'll make sure to cut the entire 2x4 but not too far into the plywood.
- Cut your mark, making sure that the saw blade is on the right side of the line. Then set the saw down with the blade in the groove you just created, centered in one of the 2x4s. Mark the right side of the saw's "table" (the flat metal or plastic base that the saw rides on) and square that line across both 2x4s.
- Fasten another 2x4 along that line (this is the "guide block"), across the top of the two bottom 2x4s ("rails"). This will guide the saw table for your next cuts.
- Remove the stop block from step 1.
- Take the board that you're cutting and slide it under your guide block from the right, between the two rails.
- Line it up with the end of the rails on the left and run the saw along the guide block to cut a block to the length you require.
- Repeat step 9 as necessary.
Consider using hand tools. If you read woodworking articles online, you would think you need a table saw, mitre saw, bench-top planer and a whole host of other power tools to do every simple task. While those things are nice to have, if you don't have them it doesn't mean you can't do anything. Since you only have 3 boards to cut, this can be done quite easily with a hand saw. A tenon saw would be ideal, and even a cheap one will do.
Mark the first board and cut it. Use the first board to mark the length on the remaining boards, and cut those.
Now, hold them up to each other. If they're not exactly the same length, then you need to trim them. Clamp them together in a row so that they all line up at one end, then clamp the row onto a workbench. Mark a line square across all the boards, and use a plane across the uneven ends to even them out.
Planing end grain like that tends to tear the wood. To avoid that, you can clamp a piece of scrap wood at the end of the row when clamping the cut boards together.