Unlike wood, plexiglass is extremely difficult to cut without breaking it and melting it. For do-it-yourself good projects, home improvement shops usually recommends an inexpensive scoring knife. Although the scoring knife works fairly well for small plexiglass, larger pieces tends to break unevenly. That is due to the physical limitation of our hands' inability to apply even pressure over large areas. After spending considerable amount of time figuring out how to cut a large piece of plexiglass at home, with inexpensive tools, I have decided to document it here for everyone's benefit.
As mentioned before, the scoring knife provides an undesirable result when used on large sheet of plexiglass. The next option is to use a powered-electrical tool to cut the sheet. A table saw might be a better idea, since you can cut in a straight line pretty easily. But the cost of ownership and the amount of storage space needed, puts it out of the reach of myself and many other home owners. After considering price and physical size, the jigsaw seems to be the best choice.
After reading various plexiglass handling documentations online, I bought a variable-speed jigsaw from a local outlet for $20 (see photo below). The variable-speed is important because if the jigsaw is too slow, it will crack and break the plexiglass. On the other hand, if it is too fast, the saw blade will create too much heat and friction and melt the plastic plexiglass.
If you want to cut shapes out of the plexglass, you will also need an electrical drill. The drill helps you create the pilot hole so that you can start cutting the plexiglass from anywhere within the plexiglass plane.
You'd think that manufacturers would sell a whole assortment of tools specifically for cutting plexiglass. But they don't. After researching a bit, I have found that there are few jigsaw blades available specifically for cutting plexiglass. However, the nearest shop that sells such a blade is in England! Luckily many folks have good experience with fine toothed sheet metal jigsaw blades.
I found that the DeWALT 32 TPI Jig Saw Blades (see photo below) worked extremely well. Originally, I bought a set of assorted inexpensive blades from the local Harbor Freight. Unfortunately, this set of blades do not work, because they were coated with paint. The paint created heat and friction, which caused the plexiglass to melt. The DeWALT 32 TPI Jig Saw Blades, on the other hand, is uncoated and worked extremely well for cutting plexiglass.
The Drill Bit
If you are planning on cutting the plexiglass from the center, or if you just want to cut a shape, you'll need to drill a pilot hole as big as the jigsaw blade. It's very difficult to drill a plexiglass with regular drill bit. To do it successfully, if at all possible without cracking the plexiglass, you'll have to go from the smallest drill bit to the bit that is the right size. Any jump in drill bit sizes will usually cause the plastic plexiglass to crack. An easy way is to get a step drill bit (show in the photo below). With a step drill bit, I've been able to drill any sized holes in the plexiglass without any cracking it.
After assembling all the tools, it's time to make the cut. The first thing to do is to determine the proper speed for your jigsaw. The only way you are going to know the proper speed is to try cutting the plexiglass. And there is the catch-22. Hopefully, you have a scrap piece of plexiglass that you can test on. If not, you might consider buying a smaller piece of plexiglass for the cutting test. Or if you are going to cut off a significant amount of plexglass from the sheet you have, you can use a scoring knife--ahhh, there really is a use for this tool--to break off a piece.
Once you have a scrap piece of plexiglass to test with, try cutting it with the jigsaw at different speeds. Do not attempt to push the moving blade onto the plexiglass until the jigsaw has sped up to the full-speed of your setting. This precaution prevents cracking the plexiglass due to the blade moving too slow. After the jigsaw reaches full-speed, push the blade against the plexiglass with a constant force. If the edge of the plexiglass is melted, then the speed is too fast. If on the other hand, the plexiglass starts to crack in all different directions, then the speed is too low.
Once you have determined the proper speed for your jigsaw, you can go ahead and cut your masterpiece. Keep in mind that the jigsaw will "walk" slightly. In order to cut in a straight line, you really have to watch where it is "walking" to and push it slightly in the other direction.
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