Cutting Holes in Poly Carbonate

[Dallas]

I have a piece of poly carbonate that I'm going to use to put the 12V and AC monitors in.
The piece is 1/4" thick and about 13" X 16"
I've thought about doing it 2 different ways,
1.) mounting the gauges, dials and doohickeys behind it, or,
2.) actually mounting above ma\entioned paraphenalia in the poly.

My question is how do I drill the holes to mount it without cracking it? Any special drill bit, speed, pressure? etc?
The next question is, if I mount the gauges in the poly, how do I cut the holes? What kind of blade would I use in the sabre saw? How fast do I run it? etc.

The reason I ask these questions is that I've cut Lexan and other plastics before and had a heck of a time keeping them from cracking.

Any experts out there?

TIA
Dallas

[Nick Badame Refrig/ACC]

Hi Dallas,

Polycarb is fairly flexable.. You should not have problems with it  as long as you back it with a substraight like wood.

Use hole saws if you have them. It's nowhere near as brittle as lexon.

Good Luck
Nick-

[Slow Rider]

Like Nick said use a hole saw if you have it, also put tape (masking) on the back and that will help the cracking/splitting.

Frank

[Stan]

Dallas: This website should answer most of your questions

http://www.plasticsmachining.com/magazine/199609/polycarbonate.html

[Dallas]

Thanks, Guys.

I didn't know if this was a brittle as Lexan or not.

This particular kind of Poly is suppose to have a harder surface than normal to resist scratching.

Dallas

[gus]

Dallas,

I don't have any experience with poly but do with plexiglas and lexan. I suspect they may be a lot alike.

The idea is to get the plastic hot with a high speed drill or saw and let the bit or blade melt its way through. This keeps it from cracking. A snagging blade or bit will crack it so always have the plastic solidly fixed.

Drill bits for plastic also have a special grind, most of the usual bit tip is ground away.

You can also nicely smooth any exposed edges with a hand held propane torch by quickly running the torch along the edge until it just starts to melt. This requires a delicate touch, never stop moving the torch.

[boogiethecat]

Actually polycarbonate IS the exact same stuff as Lexan.  Lexan is Ge's trade name for it, and they are both virtually identical.

Lexan/polycarbonate is very different from acrylic/plexiglas, which is brittle and difficult to work with.

Benefits/ drawbacks:

Polycarbonate: tough, hard to break, hard to crack, very easy to machine, easy to scratch, not very good in sunlight as it gets UV damaged easily.   The solvent cement of choice for polycarbonate is methylene dichloride but aesthetically  it's hard to glue as any solvent cements will cause crazing..  Flame polishing the edges is possible but it tends to bubble easily so go fast and be careful.

Plexiglas / acrylic: easy to crack, easy to break, difficult to machine and drill... hard to scratch, does well in direct sunlight.
Plex is very easy to glue with ethylene dichloride as solvent cement and glue lines stay clear and perfect.  Flame polishing is easy to do with plex.

When working with polycarbonate, you don't have to do much out of the ordinary to be sucessfull.  It's easy stuff to work... can be drilled, sawed, filed, routed, etc pretty easily.  If your tool is moving so fast that the stuff melts, slow it down, but this is mostly only a problem with plexiglas.  When drilling it's nice to have a backing board behind, so when the drill breaks thru it doesn't cause any local cracks... but other than that, it's really nice stuff to work with
Cheers
Gary

[Dallas]

OK,
I've been reading up on working with the stuff from the link that Stan posted.

I have a router and some sharp carbide bits. I also have hole saws but some of the panel meters are square so the hole saw won't be much use. I think if I use the router with a small diameter straight bit, I can use the sabre saw with a 32t metal cutting bit to square up the holes for placing the meters.

Now, onto drill bits.
Gus mentions special plastic cutting bits in which the central point is removed. Could I cut the tip off a HS bit with the Drill Dr. and sharpen it back to a less aggressive point, or would it be possible to use a forstner bit or even a spur bit to drill mounting holes?

I would like to raise the panel about 3/4" from the mounting frame. Gary mentions methylene dichloride but that it can cause crazing. Would I be better off cutting 1/4" X1/4" strips and screwing through them or is there some other method where I could glue the edges together like an aquarium?

As expensive as this stuff is, I'd hate to screw up what I've got and have to go get more. Mama wouldn't be amused, since it was suppose to be used to fix a broken rear quarter window in her car.

Thanks for all the help!

Dallas

                           GO BUSSING!

[Stan]

Dallas: On caution on square holes. Nice square corners are prone to starting a stress crack in most materials. I would suggest that you drill a small hole in each corner before you cut out the remainder. and leave the small radius in the corner.

[TomCat]

I've seen Lexan put in a sheet metal brake and bent, just like metal. Flame polish the edges, and you have a very slick looking, professional job.

Jay
87 SaftLiner

[gus]

Dallas,
I wasn't very plain, the point is not ground off but the flutes (I think that is what they are called) are ground down to be very thin. I wish I had a photo to show you, but your plastics dealer can show you.

From what Gary says in his excellent description you may not need these special points, they are used for plexiglas (acrylic).

[boogiethecat]

On gluing, methylene dichloride will do it but it won't be pretty.  You could use silicone just like gluing a glass aquarium, but it won't be horribly strong. The only way I've found to glue the stuff strongly and visually nicely is with high tech UV curable adhesives used in the medical industry, but that takes special glue and an ultraviolet curing system (I actually have one) that's not easy to find and not cheap either.   Lexan takes readily to drilling and tapping, so perhaps the best way to do your attachments is with screws. It's tough enough to not break this way, and it's really easy to tap.

When you're working with the stuff, try to leave the paper or plastic covering on it until the very last moment... it's amazingly easy to scratch and almost impossible not to when doing this much work to it.

I don't think you'll need any special drill bits.. as Dallas says, they are only necessary for plexiglas.  Just use a backup material as I mentioned and you'll be fine.  Try a test on a little unused corner first to get comfortable with the stuff..

Cheers
Gary