Cut a PERFECT line with a circular saw

There are times when you require a “factory cut” – a more or less perfect joint – say for a plywood wall. The problem may arise when the only tool at your disposal is your circular saw. Guides are one of those things that can be very useful during a potential crisis like this. There are many different kinds of guides, but the one I’m going to talk about here is a “homemade” one. You may also be tired of trying to cut wood following a pencil line “by eye”, and if so, this article is for you. This can be extremely frustrating, especially when the sawdust is spraying everywhere, impairing your vision etc. We all like simple and sweet right? Well, I do. And this method is tried and proven, and if you get it down, it is extremely simple. Things you will need:

1. Several pinch clamps. Depending on how long your boards are, you will need more or less. For a 2 meter board, you would want at least 4.

2. A thick, inflexible straight-edge that’s at least as long as your work piece. This can be anything, provided it is straight, inflexible, and has an edge that your circular saw can butt up against without slipping off. Remember that your cut will only be as straight as your straight-edge.

3. Last but not least, your circular saw. One thing to note about circular saws is that if they have been dropped even once, are cheap, old, or have been used roughly, their blades are often out of alignment with the base-plate. This means that when you butt the side of the base plate up against something and begin cutting, because the blade isn’t exactly parallel with the base-plate edge that you’re using as the guide, the tail-end of the blade will either swing left or right cutting out a wider area from your work piece. So instead of slicing nicely through removing only the width of the blade, it will end up ripping out much more creating an uneven cut.

For rough work this won’t be an issue, but if you want a “factory

circular saw with L ruler

Measuring distance between blade & plate edge

cut”, you’ll have to get yourself a circular saw that’s been checked for alignment. Circular saws may still “work” even after they’ve been dropped, but depending on how it fell, I can almost guarantee that the base-plate has been irreparably damaged. So taking good care of your circular saw is very important and will make the difference between you being able to use it for more precision oriented projects or not. Ok, enough on that. Let’s move on to the method by which you will achieve your “machine cut”. Now you’re gonna have to measure the distance between the right-hand side of the base-plate edge and the saw blade. (Refer to picture on right.)

This distance will vary depending on your saw, but it should be in the 25~40mm neighborhood. Again, the end result will only be as accurate as your tools and measurements, so take your time on this step. The reason you’re measuring this is because the edge of the right-hand side of the base-plate is the surface you will be pushing up against the straight edge as you cut along. So this distance is the distance you will subtract from the line you want the saw to actually cut. Don’t forget to factor in the width of your saw blade! This could be a couple millimeters. Obviously, your saw blade should cut on the outside of the line you want cut. So I’ll go over the steps in order:

1. Lay your work piece on the table. Jack up your board with junk wood so you won’t cut into your table.

pinch clamp

Pinch clamp on straight-edge with pencil mark

2. Now measure and mark where you want to cut. From these marks subtract the distance I mentioned above and make a second mark. Place your straight-edge on these second marks and clamp them down. Make sure the clamps are placed so as not to interfere with the saw as it passes. There will be times when the work piece is too wide for the center clamps (the end clamps will always reach) to pinch directly onto the straight-edge. In these cases use separate boards of appropriate length that stretch out to the straight-edge from the edge of the work piece and clamp these down. (Note that they should butt up against the straight-edge so as to prevent it from being pushed back toward the clamps by the circular saw.)

3. Double-check your straight-edge position and you’re ready to start cutting.

4. Butt your circular saw up against the straight-edge and slice effortlessly through your work piece. Take care to constantly be applying sufficient pressure against the straight-edge so as to ensure your saw doesn’t come away from it accidentally. And equally as important, make sure your clamps are holding well enough so that as you push against the straight-edge, you won’t shift its placement. Making sure your saw blade is sharp is another vital point. Using a dull blade creates resistance, causing you to apply undue force on the work piece. This results in you not being able to tell if you’re making good contact with the straight-edge. Ultimately, you run a serious risk of either coming away from the straight-edge, or applying too much force and pushing the straight-edge out of position. In both cases you end up with a bad cut, wasted time and material, and possibly a very bad remainder of the day.

Well, there you have it my friends! If you have done these steps correctly, you should have a more or less perfect “factory cut” that will fit butt to butt with any other factory-cut board. This whole process may sound difficult or time-consuming, but if you get used to it, you can learn to do it quite fast.


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