Cutting Plexi-glass w/o Splintering It

[doug hodder]

Lexan is 3M's brand name for polycarb...it is 30X more impact resistant than plex...you can even put lexan into a break and put bends into it...for cutting with a jig saw, either material,...I lay it on top of a piece of thick styrofoam when I cut it...it provides complete support under it and is a lot easier to work with...there are specific carbide blades for table saws for use on acrylics...different tooth rake and angle...plex will give you a clearer view when used as a window over poly...and larger pieces of poly will expand and contract with temperature much more than plex, probably not an issue on a tear however...It's all about tradeoffs...just my sign industry experiences...Doug

[Steve_Cox]

So how thick would the lexan have to be to make my tear bulletproof?

Mike...

This in it self is a very interesting question Mike, and with many variables. While I also am not an expert in the plastics field, the application for your bulletproofness is the primary factor. Did you want to stop handgun bullets or rifle bullets, bullets that are entering the teardrop or just the ones leaving the teardrop?

[Chris C]

Hi Chris,

You may well be right, having been in the business, but what I understand is that plexiglass is poly(methyl methacrylate) a thermoplastic polymer.

And Lexan is Polycarbonate.

Plexiglass tends to shatter/crack more so than Lexan.

The names are used interchangeably, rather like "restored" and "repainted".

They are similar, and look the same on the surface, but are different underneath.

Lexan is softer than plexi and scratches more easily, but is stronger.
Lexan is used for bullet proof windows.

Rob, who isn't an expert, but who did study hard before choosing the material for the trailer windows.

Rob, I don't remember commenting on Lexan (polycarbonate), but do know that Plexiglas is acrylic. You are correct in that acrylic is more prone to cracking and breaking and polycarbonate was designed to be much more resistant...................and in certain thickness' can be bullet proof................but usually only with a layer of 1/16" layer of soft vinyl sandwiched inbetween two 3/4" sheets of polycarbonate.

[doug hodder]

If you want bulletproof....you can always get kevlar cloth and do up your sides with that and epoxy...don't know how it would work, but that cloth is available for boat building...but I'm sure that there is more science involved than a layer of kevlar....Doug

[jo_tigger]

Plexiglass is normally cut by scoring through but this is slow and tedious. I cut mine on the tablesaw. It helps if you hold a piece of wood over the area being cut to get a smoother job otherwise the plexi tends to bounce and cut very badly. If using bandsaw or jig saw use slower speed to keep plexi from melting also applies to drilling. Scoring might not be to bad for 1/8" however just hard to keep a straight line.

Have fun

[IndyCubby]

I have cut plexiglass using a rotozip. I clamped the plexi down to the work surface with a board on top (using it as a guide for the rotozip). Makes a very clean cut....just don't let the rotozip get away from you! It likes to cut curves...you have to keep it tight against the guide board.

The table saw idea is probably your safest bet.

Good luck!

[Dean in Eureka, CA]

Todah,
The reason you are having problems with the jig saw is because of friction and heat. Use a blade that has some kerf to it if you have to use a jig saw. (I've done the start stop method to prevent the cut from gumming up, when the only tool on hand was a jig saw)
BTW- A jig saw isn't the best item to use when cutting acrylic. It's fine for poly carbonate. (Lexan)
I like using a table saw, or circular saw.
If you have to make a radius cut, you can always make a straight cut, then use a belt sander to get your final shape, just make sure you have backing paper protecting the finished surface.
You can also use a hand tool cutter also, that is basically a pull knife, that chissels out a groove, deeper with multiple passes, so you can run out the score or pop the score like cutting a piece of glass.

[Larwyn]

I made a temporary replacement window with a hole in it for an air conditioning unit not so long ago. It was a 1/4" sheet of plexiglass/lexan dont know which.

I scored it deeply and it snaped cleanly for the outside straight cuts. The radiused corners and inside cutout for the ac unit I did with a fairly coarse wood cutting blade in a variable speed jigsaw (used the lowest speed). The cuts all came out good enough, touched em up with sandpaper. Where the trouble came in was drilling holes around the perimeter, several of them cracked out the side as the bit broke through. I still do not know how to drill a hole in that stuff with confidence. Maybe some of you experts can enlighten me.........??

[asianflava]

If you want bulletproof....you can always get kevlar cloth and do up your sides with that and epoxy...don't know how it would work, but that cloth is available for boat building...but I'm sure that there is more science involved than a layer of kevlar....Doug

The secret to bulletproof vests is in the weave of the kevlar. The weave is able to "Catch" the bullet without penetration. With a standard cloth, the bullet will just go between the roving.

[Bigwoods]

mikeschn wrote:
So how thick would the lexan have to be to make my tear bulletproof? Surprised

Mike...


This one I can answer. An eyeslass lens mage with polycarbonate (lexan) can stop a 38 with a thickness of 1.5 MM. I have seen the video.

Wood and steel workers should be wearing poly for safety.

[riverfront]

We used a jigsaw on low with a fine cut blade to cut our funny car windshield - we also drilled holes for mounting - when we called the Mfg. about the cracking they said drill or cut as slow as possible with a new drill or blade (carbide prefered). And her is the kicker! AIR, yes AIR!!! They said to have a person blow air from the shop air compressor at the point of cut to keep the blade and material cool - Never had a problem again! Please wear eye protection!!! Of course we always do!

Sorry MJ - No pic's?

[jo_tigger]

I made a temporary replacement window with a hole in it for an air conditioning unit not so long ago. It was a 1/4" sheet of plexiglass/lexan dont know which.

I scored it deeply and it snaped cleanly for the outside straight cuts. The radiused corners and inside cutout for the ac unit I did with a fairly coarse wood cutting blade in a variable speed jigsaw (used the lowest speed). The cuts all came out good enough, touched em up with sandpaper. Where the trouble came in was drilling holes around the perimeter, several of them cracked out the side as the bit broke through. I still do not know how to drill a hole in that stuff with confidence. Maybe some of you experts can enlighten me.........??

Use a drill press with a block of wood under the plexi and clamp it so that it does not move around while you are drilling. A sharp bit helps and I like to backout and clear the shavings as I go. This also gives the bit and plastic a moment to cool. I like the idea of spraying air as you go except I got no one to hold the hose. I guess one could rig it up to the press so you would not need an extra hand. The most important part is the block of wood under the hole to support it and protect it from cracking as it breaks through the blastic. I'm assuming you are talking about small holes.

Just another experts opinion

[48Rob]

Chris wrote;

Rob, I don't remember commenting on Lexan...

Chris,

You are correct, you did not.

Without question, it was my mistake.

Rob

[Chris C]

Deleted.

[Todah Tear]

Thanks guys. I'll let you know how this next window turns out. I've already cracked one. That's what spurred the plexi-glass question. Just for grins, I may try to fix the crack with a heat gun.

Todah