I was asked a LONG while back how to get accurate cuts with a saw. One of my readers was frustrated with building because she was wasting wood by getting cuts that weren’t what she measured. Nothing is more frustrating than ending up with material you can’t use–or trying to build with boards that aren’t accurate. So here is the long-overdue post on getting accurate cuts with a saw, every time.
First off, I recommend that you come up with a system to keep all your measuring and cutting supplies handy. I talk about that in my How to Cut Plywood with a Circular Saw video. You will be doing this measuring and cutting business over and over and over, so make sure you always put your eye & ear protection, pencil, tape measure, and square in the same spot every time you use them. You can waste a LOT of time looking for these things and coming up with a system that works for you will pay off big time in the long run! And use that safety gear. Every. Time.
Now for the fun part! Begin by making a fresh cut on one of your board ends. Look for staples in the end before you do this and remove them with needle-nose pliers or by wedging them out with a screwdriver. Push your board snugly up to the fence (on a circular saw just make sure you are snug up to the straight-edge cutting jig or whatever you are using to get a straight cut) and slice off a sliver of the end to make sure it is square and smooth:
Now you use that fresh end as your starting point, and measure from there out to the length you want the board to be. I use a mechanical pencil so that the end is always sharp and my line is as skinny as I can make it. Make sure the measuring tape is square to the board–on a board this size I eyeball it, on a piece of plywood I use my square on the “freshly cut end” to keep the tape measure straight.
Make a small mark right at the length you want to cut.
Then use a square to mark the entire line.
It is easy to mix up which side of the line you need to cut from and it is very important to make sure you don’t do that for accuracy. The saw blade is narrow, but it does eat away some of the wood when it makes a cut, and that is called the kerf. If you put the blade on the wrong side, your board can be around 1/8″ (depending on your blade’s width) too short. I mark the waste side of the board with a “V” and then I know to line up the edge of the saw on that side of the mark.
Now you line up your saw blade to the right of the mark. It looks like it is not accurate from this picture (the blade looks like it is slightly too much to the right) but it is because of the camera angle. You will be able to line yours up perfectly. The black arrow would be your pencil “V” mark.
Here I stopped the cut before it went through to show you what I mean by the kerf. If you had put the blade on the wrong side of the mark, that much of your measurement would be cut away. This is true on any saw you use. The kerf is also the reason that you want to measure, mark, cut and repeat for every cut you make, rather than measuring and marking all your cuts and then cutting them. You are not going to be able to do that accurately.
Begin with a sharp blade (I have an 80T blade on the miter saw and 40T on the circular saw). You might need to clean off the blades if you are cutting a lot of pine because of sap build up (I’ve never done this, but I’ve heard that). Use a smooth motion and constant, steady speed for a smooth cut. If you smell a burning smell then speed up–if you are getting rough cuts then slow down. And practice makes perfect!
Another problem with accurate cuts can be due to your blade not being at a right angle to the base. I think I am going to look into this the next time I use my circular saw. I saw a YouTube video talking about how to adjust your circular saw blade to 90 degrees and I plan to check out my saw and adjust as necessary. I think that is going to improve my cuts even more!
Next up: the tools I started out with since I’ve gotten some comments/emails about that recently. It can be overwhelming trying to decide where to begin!