Cutting lexan

[Mad Dog]

OK, the 3/8" lexan arrived today and I'm pondering how to go about cutting it up.

My last experience cutting plastic (I think it was plexiglass) was unpleasant - chipping, shattering, splintering and an unpleasant screeching noise.

It would be nice if I could do this on the table saw - I have a new steel plywood blade. I've got a bench model band saw but I have difficulty cutting in a straight line.

Do you think that Rigid 10" 50 tooth carbide blade could do the job. Apparently it is a super value and I've been meaning on picking one up but funds are somewhat low.

Another alternative would be a hand saw maybe.

Any thoughts?

Cheers

 

[Splint Eastwood]

I bought an Oldham 8inch 150tooth blade from Home Depot (not expensive, @$15 I believe) The grind is made especially for cutting plastic and aluminum. Not high end blade, but how often do we need?

Make sure, esp with cutting aluminum that you wax up the blade!

I have had good experience with this blade.

M

 

[CarvedTones]

I read your other post - you are making a single blade guard, right? I would use a hand saw, specifically a fine tooth pull saw. If I had a bunch to cut, I would consider other ways (power). I would take a straight edge and a utility knife and score it first. I would cut off an un-needed piece first to practice. Even handsaw friction will get it "melty" if you don't go slow and/or pause a few times.

 

[CarvedTones]

Haven't I heard or read somewhere about putting the blade in backwards?

I think they have to do that South of the equator... :rotflm::rotflm::rotflm:

 

[Gofor]

Lexan cuts fine on a table saw with a 60 tooth blade (have not tried 50). I have cut 1/16" up to 1/4". It is a polycarbonate, so does not shatter like plexiglas. Plexiglas, because it is brittle, is better cut by scoring both sides and snapping it off like you would do glass, altho the scoring must be deeper (have done many cuts on 1/4" and up to 1/2" this way). Lexan is a lot tougher and more flexible, so scoring does not work as well as cutting with a blade. If you have a ZCI, you may have to clean a bit of melted plastic off it after the cut.

Go

PS to smooth the edges, a sharp block plane works well

 

[Mad Dog]

Many thanks for the advice.

I ended up buying a plywood/plastic cutting blade. I can use it for cutting up plywood later on.

I ripped the parts with my newly created (ar, ar) zci insert with integral splitter. Then cross cut, using my new sled, ar, until the parts got a little too small for safety and then used my dove-tailing hand saw. No problems.

Drilling this stuff is different. I think the best way is to get the drill up to speed and then in and out quickly, otherwise the stuff melts and quickly solidifies and you can't get the drill bit out! Tapping the 38 holes was getting a bit old so I put the tapper in the drill (ha, ha). Unfortunately, the tapper got stuck and when I tried the vice-grips to get it out, the tapper snapped in two. So then I got mad and tapped the remaining holes with the machine screws - worked better than the tapper - screw in about 1/8", back it out and then back in all the way.

OK, so I've got the guard assembled - its not pretty but it is functional.

Cheers

 

[fergy]

Wood bits don't work for drilling it well at all, as you can see. You need a special grind for it, and something like a 60-degree tip angle. The bits need to scrape, not cut.

For tapping, I usually drill to the next-sized letter bit, instead of the recommended tap drill bit. I usually tap with a drill as well, but I dip the bit in cutting oil, and it makes all the difference. You can also use wax or tallow, if you've got it laying around.

I had written up a long post about what blade to use, but it was apparently deleted. Go figure.

 

[Alan in Little Washington]

You can also clean up the edge of acrylic and polycabonate on a jointer.

 

[Skymaster]

I use my jointer. That said and this IS REAL. The way it is done in shops etc that cut this all the time is with a torch! YES if you have a bernzomatic keep it about 3 or 4 inches from the edge and move steady and no hesitation at a fairly good speed and it will "flame polish" . If you guesstimate about 2 secs for a 12" run it should be about right. Better too fast and do it twice. too slow it will burn

 

[fergy]

plastic fabrication shops use jointers for edge prep prior to gluing using solvent methods, since it leaves a cleaner edge than the saw. That's what I do when I need to have an optical seam in a piece.

As for flame polishing, that's done with a hydrogen rig, not propane. It's a special rig that's made for jewelers. Hydrogen/oxygen burns clean and at the proper temperature to flash the edge. Propane is too cool, so you wind up heating too much and getting the scorching problem because you can't move fast enough. The problem with flame polishing that it induces surface tensions in the plastic, and if you ever get any sort of solvent or alcohol near the plastic, it crazes, meaning the surface gets covered in tiny fractures. That's why you can't polish like that prior to solvent cementing. The same happens if the pieces get too hot in the machining process and don't get annealed prior to cementing. Nothing is worse than having that happen on a nice piece of 1" thick material when you are welding it. I prefer pieces that are run through an edge polishing machine, or hand-polished, because they look so much better and it reduces the risk of crazing in the future.

Just some tid-bits of plastic trivia from someone who use to do a lot of acrylic fabricating.