Plexi Glass - I hate you!

NoahsArcade

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I hate drilling/cutting plexi glass more than anything in the world. Im starting to think I make it harder than it really is. I usually crack or chip one of the holes 20% of the time. I convert a lot of GT and Konami games into 1xxx's so the plexi is usually too big to fit under my drill press, meaning I have to hand drill each hole. The plexi I use is pre sealed pretty nice. I always tape everything just in case. Just curious what methods and bits other people use. Maybe Im overseeing something obvious or there is a tool that Im not aware about.

Im having one of those days where the very last whole I drilled I fucked everything up. Nothing like pissing away 15 bucks and 2 hours of work.
 
I use a high speed tool, like a roto zip or similar, to had cut everything. The key is a very high speed RPM.
 
I use a hole saw with the arbor bit snapped off and use the pre-drilled cp
attached to the plexi as a guide.

I usually end up with a lot of melted crap around the hole afterward,
but it comes off easily with a knife and semi-round file.
 
I might be speaking out of my ass, but I thought masonry bits worked really good for plexi? :confused:
 
I also suggest when you drill a hole. Only drill 1/2 way through and then turn over and finish the hole. This will eliminate any chipping or cracking.
 
I finally got plexi for my showcase CP (this project will never end..) I was wondering can I just run my hole saw bit through it? I heard something about running those in reverse, makes it melt through or something.

I don't have a scoring tool, think I can get away with running a box cutter along the edges I need to cut off?
 
I hear you. EVERY plexi control panel I've had to drill has had one crack where I pressed to hard too fast. Usually the first hole I drill is the one which gets cracked.

Then, I usually remember how I did it before and it doesn't happen again.

I'm usually using 1/4" plexi as a CP cover, so I always make starter holes with a small (maybe 1/16") drill bit as a guide. Then follow those up with the appropriate sized drill bit for carriage bolts to go thru. The fine tooth hole saw has an easier time lining up if I go in these small holes for the buttons as well.
I always go slow, letting the bits do the work. Sand of the "scruffies" left over from the bits. I never have any cracks once I drill the small holes, then the bigger ones.

I also use a dremel with a sand-paper attachment to carve and shape any curves or strange interior shapes as well.
 
For small holes, I usually mash it between two boards (or one board on top if it's already on the CP), then drill through the board and plexi, and the boards keep it from crawling up the drill bit and cracking. For the large holes (that I use a hole saw for), I do a small hole in the middle mashed between boards like above (for the drill bit of the hole saw), then just use the hole saw, except as CalifTom said, go half way, then flip and do the other half.

DogP
 
I do one of two things. I either stick it between two pieces of wood and use a hole saw and drill it high speed backwards...

...or I use Lexan... that stuff ROCKS...you can cut through it with just about anything and not worry about breakage.
 
I always drill the screw holes in the plexi first and then install the plexi on the CP. Then I just drill straight through with a holesaw. If you drill with a hole saw in reverse it tends to make a cleaner hole and you don't have as much melted plastic around the whole.

The key to not cracking the plexi is to not apply too much pressure and to have the CP underneath supporting the area around the hole.

If you don't have anything supporting the plexi underneath around the hole area the plexi will flex underneath. This along with the pressure from the drill causes the plexi to crack.
 
Large Holes : Hole saw with just the very tip of the guide bit extended. I place another piece of scrap plex behind the piece I am drilling then place both of those on a piece of scrap plywood or particle board.

Small Holes : Normal drill bit at a moderate speed with steady pressure. Again, with a scrap piece backing it. I also tend to take a larger but and chamfer out the hole if I am using a screw with a collar under the head. Otherwise, when it makes its own space it will generally crack to plex.

Wither size hole....practice to get your technique.
 
I will admit most of my success is with a thicker plexi. I have 1/4" on most of my machines but sometimes I try taking the cheaper route with these saleable multis and go with the 1/8" stuff. Sometimes trackballs and 1/4" arent ideal but its just a fraction of an inch off so its usually not too noticeable.

I hear ya on the showcase control panels. Ive dont several multi conversions with those. I recently did a 4 player/trackball layout and put an 2 inch crack in it on the second to last hole drilled. Luckily the customer didnt mind. Seems like rebuilding the CPs is the most labor intensive part of these stupid conversions.
 
My advice would be to determine that actual type of sheet plastic you are using, as each requires different techniques.

Plexiglass is a brand name. Plexiglass = acrylic plastic (polymethyl methacrylate), which is commonly found in two types: extruded, and cast. Extruded is softer, more prone to melting, but less likely to chip. Cast is very hard, and more likely to crack/chip in a manner similar to glass. Softer = easier to scratch. Lexan is also a brand name. Lexan = polycarbonate, and comes in varying grades for different applications.

Acrylic vs Lexan: More likely to chip, doesn't scratch as easy, doesn't yellow over time.

Lexan vs Acrylic: More expensive, scratches easier (softer), less likely to chip, turns yellow over time from UV.

Now that being said, I would use cast acrylic and a router. The best way to get the cleanest smoothest results would be to use a panel pilot bit with a plunge router and jig. Jig would be a piece of plywood, with a template hole to follow, and big enough to easily clamp your plastic to. This method may be overkill for most, but if you have the tools the results are worth it.

Router speed is also key; in theory when cutting acrylic you should have little to no melting. This can be achieved with low spindle speed (slowest your router can go), with a high feed rate (how fast you can safely follow your jig). To finish the edges, a light sanding with 220 grit sandpaper, then onto a flame polish (using a propane torch to lightly melt the edges, giving a finished look).

Maybe I'm just getting too used to having a cnc router for doing these things ;)
 
plexi

Go slow and it will be fine every time.

For larger holes use a step drill bit #8 from home depot, etc for button holes.
 
My advice would be to quit F'n up cabs and putting 1xxx in 1s in them, that will solve your plexi cracking problem.

my .02
-Ken

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