How do I cut a perfect circle into a piece of clear plastic plexiglass?

I need to cut two circles with diameters of 80mm and 120mm. I own hardly and tools, and would like to not spend more than twenty dollars to do this. any suggestions?





THANKS!!How do I cut a perfect circle into a piece of clear plastic plexiglass?
Measure the glass end to end on four sides; that gives you the middle


Use a magic marker (fine point) put a string on it at the middle mark and holding the pen in place make a circle with the string out to the desired circle you want. Hope you understand this.Plexiglass is best cut with a wood burning set using the knife blade. They are about $15.00 at Wal Mart or Michaels.How do I cut a perfect circle into a piece of clear plastic plexiglass?
In the US you can buy ';hole saws'; that are run in an electric drill. I know you can buy up to 4'; which would be 100mm because I have one. You may be able to buy larger. Lacking that, you could cut the hole with either a router with straight bit or a sabre (or jig) saw by building an attachment that would allow you to turn the tool upon a central pivot point.
Keep in mind that a lot of ';hole saws'; have a regular drill bit in the center to make a pilot hole. If you don't want a hole in the middle of your circle, make sure your hole saw, if that's what you end up using, doesn't have the center/pilot bit.





I've never heard of using a wood burning tool to cut plexiglas, but it has me intrigued. If you try that method, be careful you don't MELT the plexi in the process.





You might be able to rent tools from a home improvement center, which might be cheaper than buying specialty tools that you will only use once.





Have you priced having it done at a glass shop? You might be able to do it for under $20, especially if you already have the plexi and all they have to do is take 5 or 10 minutes to make the cuts...





I'm dying to know ... what are you making???
You can use a drywall circle cutter for plastics. I left you a link to one that costs about $6. For cutting plastic with it, just keep moving the arm around the circle with slight pressure until you get cut all the way through the material.
I build speaker boxes, and would LOVE to know how anybody cuts perfect circles in anything... I eye-ball it with a jig saw and luckily have a steady hand...





Sorry, i can't really give any great advice here... I am very interested in the answers of others tho...
buy the right size hole saw for your drill...leave the pilot bit in as it wont make a difference in your case...