Cutting Plexi-glass w/o Splintering It

Anything to do with mechanical, construction etc

Postby doug hodder » Tue Jun 13, 2006 8:49 pm

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
doug hodder
*Snoop Dougie Doug
 
Posts: 12625
Images: 562
Joined: Tue Dec 14, 2004 11:20 pm

Postby Steve_Cox » Tue Jun 13, 2006 8:56 pm

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

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? :D
Steve
User avatar
Steve_Cox
4000 Club
4000 Club
 
Posts: 4903
Images: 196
Joined: Sun Apr 03, 2005 8:46 am
Location: Albuquerque New Mexico

Postby Chris C » Tue Jun 13, 2006 9:37 pm

48Rob wrote: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.
Chris :D

The tension between what is good enough and what is beyond that creates the space for character to become our work.

Teardrop Trailer Build Pictures: http://tinyurl.com/px5cd
Chris C
.
 
Posts: 3302
Joined: Sun May 15, 2005 7:24 pm
Location: Norman, Oklahoma
Top

Postby doug hodder » Tue Jun 13, 2006 9:41 pm

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
Last edited by doug hodder on Tue Jun 13, 2006 9:44 pm, edited 1 time in total.
doug hodder
*Snoop Dougie Doug
 
Posts: 12625
Images: 562
Joined: Tue Dec 14, 2004 11:20 pm
Top

Postby jo_tigger » Tue Jun 13, 2006 9:43 pm

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
Richard
Austin, TX
jo_tigger
Donating Member
 
Posts: 17
Joined: Sun Mar 26, 2006 1:51 am
Location: Austin, TX
Top

Postby IndyCubby » Tue Jun 13, 2006 9:56 pm

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!
4x8 Cubby
"Finished" October, 2005
Gone, but not forgotten!
User avatar
IndyCubby
Teardrop Master
 
Posts: 210
Images: 16
Joined: Fri Sep 09, 2005 1:28 pm
Location: Indianapolis, Indiana
Top

Postby Dean in Eureka, CA » Tue Jun 13, 2006 10:59 pm

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.
User avatar
Dean in Eureka, CA
The Fogcrawler
 
Posts: 4997
Images: 69
Joined: Thu May 11, 2006 8:44 pm
Top

Postby Larwyn » Tue Jun 13, 2006 11:19 pm

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.........??
Larwyn

Keeper of the Most Out Of Control Shop (2005)

I feel bad for the man that cannot spell a word more than one way. Mark Twain
User avatar
Larwyn
Mad Kilted Texan
 
Posts: 1658
Images: 210
Joined: Sun Jun 20, 2004 12:06 pm
Location: Kerrville, Texas
Top

Postby asianflava » Wed Jun 14, 2006 12:18 am

doug hodder wrote: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.
User avatar
asianflava
8000 Club
8000 Club
 
Posts: 8412
Images: 45
Joined: Mon Aug 02, 2004 5:11 am
Location: CO, Longmont
Top

Postby Bigwoods » Wed Jun 14, 2006 12:18 am

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.
Greg in Northern Minnesota

Image

Image
User avatar
Bigwoods
500 Club
 
Posts: 602
Images: 104
Joined: Thu May 27, 2004 10:45 pm
Location: Northern Minnesota
Top

Mfg. Directions!

Postby riverfront » Wed Jun 14, 2006 12:39 am

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?
Bruce
User avatar
riverfront
Teardrop Master
 
Posts: 268
Images: 2
Joined: Wed Mar 15, 2006 4:06 pm
Location: Illinois-Sterling
Top

Postby jo_tigger » Wed Jun 14, 2006 1:33 am

Larwyn wrote: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
Richard
Austin, TX
jo_tigger
Donating Member
 
Posts: 17
Joined: Sun Mar 26, 2006 1:51 am
Location: Austin, TX
Top

Postby 48Rob » Wed Jun 14, 2006 5:49 am

Chris wrote;

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


Chris,

You are correct, you did not.

Without question, it was my mistake.

Rob :oops:
Waiting for "someday" will leave you on your deathbed wondering why you didn't just rearrange your priorities and enjoy the time you had, instead of waiting for a "better" time to come along...
User avatar
48Rob
Super Lifetime Member
 
Posts: 3882
Images: 4
Joined: Thu Nov 17, 2005 6:47 pm
Location: Central Illinois
Top

Postby Chris C » Wed Jun 14, 2006 8:33 am

Deleted. :?
Chris :D

The tension between what is good enough and what is beyond that creates the space for character to become our work.

Teardrop Trailer Build Pictures: http://tinyurl.com/px5cd
Chris C
.
 
Posts: 3302
Joined: Sun May 15, 2005 7:24 pm
Location: Norman, Oklahoma
Top

Postby Todah Tear » Wed Jun 14, 2006 12:38 pm

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
"It is not good to have zeal without knowledge, nor to be hasty and miss the way." Proverbs 19:2 Image
User avatar
Todah Tear
Platinum Donating Member
 
Posts: 1723
Images: 282
Joined: Mon Feb 13, 2006 3:30 pm
Location: Texas
Top

PreviousNext

Return to Teardrop Construction Tips & Techniques

Who is online

Users browsing this forum: No registered users and 9 guests