I need to cut a curvein a sheet of plastic 3/32’ thick.
I tried with my sabre saw with a fine blade but it chipped off a piece.
Need to know how to do this. I am working on a test piece but the sheet will be
2’ x 4’
Thanks in advance for your help
Harold
Harold,
I have a set of metal shears that I use for cutting thick plastic. Just did a piece last night very similar to yours. They are designed for cutting curves in sheet metal, but will work for everything but the thinner plastics. There are a pair because the blades for right- and left curving are opposite. They can also cut straight and are able to alternatively send the pieces in different directions as you cut, so are handy to have. You may find them at a cheap outlet like HF, but my brand name ones are made by Wiss, will likley cost ~$20/each or so. You really only need one to cut a circle, so depends on whcih one whether you’re right- or left-handed.
Harold,
You didn’t mention what kind of plastic you are cutting? If it is styrene or other soft plastics the shears will work just fine, but if it is Plexiglas or Lexan polycarbonate the shears will most likely chip and crack it. You would have to use some type of fine saw in the sabre saw or a very good sharp scriber made for the hard plastics. Also, be sure to put masking tape over the cutting area as it will reduce/prevent chipping; again if it is the harder plastics.
-Bob
Yeah, the hard, clear stuff - plexi, Lexan, etc - almost requires special tools. A very fine blade on a bandsaw can work, because it’s always pulling in one direction against the hard surface of the saw table. Something like a jigsaw may not work, as it’s back and forth in two different directions.
Scribing and snappping works well for straight cuts in that stuff, after a little practice, but cutting a circle will be very tricky.
If in doubt, most plastic supply houses can cut stuff and have the tools and experience staff to handle those difficult plastics.
I think it is a poly. It is the cheaper stuff from Home Depot next to the Lexan.
Harold
A jigsaw with the proper blade should work - you just need to secure and support both sides of the plastic. Sandwiching the piece between two pieces of plywood should do it. Or even two pieces of scrap plastic. Anything to keep the workpiece from being lifted up on the upstroke of the saw and snapping down. If you can drill a whole in the middle, anoother option would be to rough cut it, the mount the piece to a board of some sort with a bolt through the middle. Clamp it the desired radius away from a sander, belt, disk, or drum, and then spin the piece on the axis and sand to the final size. Same sort of thing could be done with a band saw to make the cut accurate.
–Randy
There are special blades for various plastics.
You might try these:
http://www.tapplastics.com/product/supplies_tools/plastic_tools_supplies/saber_saw_blades/570
Ed
Harold,
OK, it’s actually acrylic, although it’s commonly called plexiglass. IIRC, plexiglass is someone’s brand name for it? In any case, same procedure to cut it.
Yeah, you’re going to need to use special measures. I desribed how it’s typically score (with the special cutter they sell next to the plastic rack usually) and snap for straightlines. I’ve had real mixed success doing more than that. Randy’s suggestion of sandwiching and using a fine-blade in a jig saw may work for you, as it would eliminate the flexing that is an issue with the jigsaw alone.
Be cautious with this stuff, as it is sharp if it breaks.
Working with acrylic windscreens and windows in light aircraft, I use a cut-off wheel in a die grinder and a hand linisher and/or a sanding disc in a right angle die grinder for finishing. I would think that the similar appropriate tools in a Dremel would do the trick.
Cheers, the Bear.
Bear,
Does running the cut-off disc slow avoid melting the acrylic?
I don’t run the cut off disc slow at all, Mike. I’m not sure what the actual R.P.M. is, but I use a thin 3” metal cut off disc in a Blue Point 155 pneumatic die grinder at the shop pressure of 120 psi. The swarf is definitely warm but the acrylic is being cut not melted.
This method has served me well over the years but I must admit even now before I start I take a deep breath, especially if the compound curved window has been rushed in from the States at great expense and the customer desperately needs his aeroplane.
Cheers, the Bear.
I use the same method, but not for Aeroplane windshields. One of My die grinders run at 18,000 rpm and I actually want the cut to melt slightly…it tends to lubricate the cut…then followed with a drum edge polisher. You do not make the cut exactly on the line, leave about a 1/8’’ to sand and polish.
I suspect… for the OP… a router arc set-up with a double edge plastic bit would be the best. Takes longer to set up with a jig, than to cut it. It would also be easier to cut Lexan, than cheap fiberglass…fiberglass will crack quicker… that one reason, You want the cut to melt sligthly.
A pro at the Chicago Boy’s club I belonged to back around 1954, taught us some of those tips, on bandsaw’s,Lathe’s and router’s for cutting many plastic’s. Was fun…Made My Mother flower’s from different color plastic’s back then.
I also have the tools and scissors to cut out clear Lexan RC car and truck bodies, again You make the cut about 1/8’’ away from finish line and dress the cut.
This is the type of router bit You would want to use…might be more than what the OP wants to spend though;
Take Care! [:D]
Frank
Bear and Frank,
Thanks. I suspect cutting a circle is still going to be a challenge. The special tool and set-up that Frank described sounds like the most likely way to getting a clean cut with a circle. The expense of the tool reminds that it may just be easier to ask a plastic shop to do the work for you.
Harold,
You also didn’t describe what kind of curve you are cutting. If it is a true circle then you could use a router, if you have one, and a trammel bar or other tool for cutting radius cuts. It would also be very accurate and smooth. It would really help to know exactly what kind of curve you are cutting.
Everyone’s comments and suggestions are all very good advice, we just don’t know what your tool/equipment inventory is and your skill level as well. Just want to make a better recommendation with that data.
I have made some very elaborate setups to make a single cut but one that had to be right.
-Bob
Thanks guys
Let me desribe in a little more detail what I plan on doing.
I am creating an special effects area over a mountain scene. The plastic was going to follow the curve of the mountains. From reading all the post I have decided to go in a different diriction. As the largest area that will be covered with the plastic is 20" down to 10" 4 feet long I have decided to cut a hole the lenght or the mountain back and slip the finished plastic (48’ x 24’ Sheet) down from the top an mount it.Then finish the mountain back to the plastic.
The scene will consist of lightning and thunder over a mountain range. I have already created a lightning bolt on my test plastic by using white glue to match the shape of the bolt, priming over the scene including the White glue. Once the paint was dry the White glue does not stick to the plastic so it pealed right off leaving the clear plastic in the shape of the bolt. I am then going to use a small strobe light behind the bolt trigered by a push button on my control panel. The thunder is being created by a sound file that will be put through a Sub woffer.
If any of you guys have done this I could always use some good advise.
Harold
Harold,
Great idea! I had wanted to do a similar thing with my layout but I was going to use a sheet of translucent mylar (drawing sheets I had from my job) that are only .010 thick. I planned to cut an opening in the backdrop (1/8" masonite") and cement the mylar over it, then paint the sky background over the mylar and masonite. The opening would have the lightning bolt backlit and show thru the painted sky. Never got to do this so I am anxious to see yours. I like the idea of using a strobe light; very bright and quick flashes. Let us know how it turns out, with photos? Good luck.
-Bob