how do i cut plexiglass?

[Import_sounds-of-mid-GA]

Hopefully soon I'll be able to get some plexiglass for the back window, how should I cut it? What do i use? What should I use to seal between the glass and the top?
Thanks in advance

[Skyman]

Evan, I have cut plex successfully with a jigsaw. Use a blade with small teeth to get the smoothest cut. You can draw your pattern right on the plex and cut away. Use some fine sandpaper around the sharp edges being careful not to scratch the surface (if the protective backing has been removed). It is best not to remove the protective backing until after install.

Kyle

[MH69Dats]

I've cut plexiglass for a fish tank using a table saw. I turned the carbide blade backwards. A little 'country' I know, but it was quick and efficient!

---Marty

[Import_sounds-of-mid-GA]

i was thinkin a jigsaw... just wanted some more opinions!
how bout something to seal?

[Skyman]

I would check out a local auto glass company. They may have some good cements that will work with plex. Other than that, silicone?

Kyle

[sunbeam590]

Hi Evan, I have cut lots of Plexi using an angle grinder, a 4inch one.
just cut all the straight areas, and take small cuts to do all the curves,
you will need to clean and sandpaper all the edges, if you have some scrap have a practice first..
Cheers Kev...

[sunbeam590]

Hi Evan,
I forgot to mention that you use an ordinary steel cutting disc.
There are a few good sealants available for putting windows etc in cars,
best to ask at a panel shop, I would be carefull about using Silicone as most are acid cured, a no, no, on motor cars.
Hope this helps Kev...

[Import_sounds-of-mid-GA]

Thanks Kev,
I think Im goin to try to find our jigsaw and get my dad to help with the cutting.... I need to get to work on the template though. Thanks everybody!

[DatsunBucky]

I recently cut some polycarbonate using a jigsaw. "Lexan" is the GE brand name for polycarb, but I was using another brand.

The saw had a fairly coarse blade (12-14 tpi, I think) but the cut was really smooth. Only problem was even though I hadn't removed the backing, and taped the bottom of the saw, I still ended up with a scratch in the poly. I think the blade pulls the saw down on the material, even though you're not trying to push down. Maybe several layers of tape would have helped, but I didn't have a need to make another cut.

I used a file and sandpaper to do the final shaping. Polycarbonate is softer than plexiglas, so more scratch prone, but will make tighter-radius bends without the crazing, if that's what your need is. Plexi will scratch.

If it's a flat pane of glass, like for a hard top, consider having a glass shop cut you a piece to size. It's a bit heavier (and prolly more expensive), but you can clean it all day long without worrying about scratches.

[Russell Roach]

Evan,

If you do happen to cut and make some scratches, use mothers mag wheel polish on them it will take them out.


Russell

[dbrick]

Evan, make a full size template, exact size of the opening. What you do is double stick tape the template to the plastic (With the protective paper or plasticstill on it) and then use a router with a ball bearing template bit. The bearing on the top, the silver part, follows the template and the bit cuts the plastic perfectly. Play around on some scrap, routers only cut right in one diretion, Left to right I think, been a while.

Polycarbonate/Lexan is a good choice. Just bolt the bottom bar on after it is all in the roof.

Great for doing speaker boxes, door panels, anything where you can make a 1/4" thick template. Can also use a bottom bearing type, but they are harder to set up.

As far as sealant, butyl tape seals well, and I think GE aquarium sealer is plastic safe.

[futuredeadguy]

Evan:

I've cut more plex than I'd care to admit. I built architectural models with it daily for about 7 years.

Buy plex that still has the backing paper on it and leave the paper on it when you cut. Don't get the kind with clear plastic backing. It's junk. The paper is also a good backer because you can draw your design on it with some accuracy.

The three best ways to cut, in order of preference...

Laser cutter. Requires CAD work and laser time. The end product is perfectly cut and has a smooth edge that needs no finish work.

Table saw with a triple chip blade. Some plex is softer than other plex, depending on the brand. Some cut better with the blade set high, some cut better with the blade set to just above the plex thickness. Buy enough to experiment with before cutting the final piece. Definitely wear safety glasses. The cheaper types chip when cut on a table saw and can send shrapnel flying.

Score and snap method. Use a straight edge and score the plex on one side with a utility knife. Then set the score line facing up on the edge of a table. Hold the plex to the table with one hand and snap it downward with the other. This works on plex up to 3/16" thick. Thicker than that, your results won't be very good. This method works best on lower quality plex. And when I say lower quality, I mean from a machineability standpoint.

Jigsaws are bad for plex that does not have backing paper. It scratches the plex more than any other method, mainly because of the vibration and because it's very easy to get shards of cut plex between the base plate of the saw and the plex when you cut it.

The router methods mentioned above in the thread give excellent results, but require more setup work and are more suited to mass production. If you have access to a decent table saw and a tabletop disk/belt sander to clean up the edges and round the corners as needed, that's your best bet for your type of one-off project, IMO.

Plex is more machineable than any other product in my experience, at least most of it is. Some brands melt when you sand them. ACRYLITE, made by a company named CYRO, is the best I've ever used. Your local plastics supplier should have it. It sands and cuts like a dream, but it does make lots of dust, so wear a mask.

The stuff you get at places like Home Depot, etc. is usually not the best plex. Go to a plastics supplier. They're in the yellow pages. They'll also sell you your plex for much less than the regular retail folks.

Jim

[Import_sounds-of-mid-GA]

Thanks Jim, awesome info.... I still havent called around, but after I get the motor mount and the motor is back in Im gonna start.

[dbrick]

Everything Jim said is right on. I use a jigsaw, but I have a piece of plastic on the saws base. I was thinking about the router, you would have to rough cut it to within 1/4 of the pattern with a saw and you have to go slow enough with the router not to melt it. Do you have a wood shop at school? a BIG bandsaw cuts plastic nicley.
Main reason I suggested the wood pattern was so you would know the pattern fit perfectly in the top before you cut the plastic to size and not have to waste a piece of plastic on a mistake.
Might want to do that anyway if you use it as a router pattern or not.

Make sure you cut it a little smaller than the opening in the top to allow room for sealant. I was thinking butyl tape might be good, it's what they use to put in windshields. VERY sticky once it is compressed, but it doesn't compress much. comes in a roll, you can get different thicknesses.