Working with Plexiglas

Rocket75377 · Post by **Rocket75377** » Fri Jul 13, 2007 10:19 am

How can I attach metal to plexiglas? I want to attach a bracket to a flat piece of 1/16" acrylic. I know that I could drill it and use screws, but I've had, uh, "bad luck" drilling and cutting plexiglas. Glue? Goop? Duct tape? Thanks.

Dork · Post by **Dork** » Fri Jul 13, 2007 10:26 am

Lemme guess, it cracks when you drill it? I can think of a few things to try:

-Use polycarbonate instead of plexi
-Use much thicker plexi
-Use Goop to glue it
-Clamp two pieces of wood around the plexi before drilling. Drill through the wood and plastic in one shot. This should keep the plexi from bouncing around and cracking. For attaching the bracket with screws you'll need plates on both sides of the plexi to spread the load.

EspressoDude · Post by **EspressoDude** » Fri Jul 13, 2007 10:28 am

LEXAN (POLYCARBONATE ) is far more forgiving than acrylic as far as drilling and breaking...It is used as football helmets, bus shelters, etc.
It won't shatter if you hit it with a BFH.

Lexan is a GE trademark "GE brings more good resins to life"

Toolmaker · Post by **Toolmaker** » Fri Jul 13, 2007 10:40 am

Ya need to regrind your drill to cut plexi/acrylic. A much "sharper" point is needed to avoid the big round chip from breaking out of the ass end. If you have a mill and can clamp your material you could use a 2 flute end mill to drill. You could also try some masking tape on the back side. Here are a couple webpages to help bring ya up to speed on plastics.

http://www.plasticsmag.com/features.asp ... Sep/Oct-01

http://www.wingsandwheels.com/Installation.htm

http://www.hawkfish.org/snailman/acrdrill.htm

My second choice would be an epoxy or goop depending on strength requirements.

Post by **mdmf007** » Fri Jul 13, 2007 11:12 am

PLexi epoxies well. Devcon makes some eoxies exactly for plex / metal applications.

You can drill it, but need to use a sharp bit, pilot pointed bits (looks like a 2 stage drill bit)

good luck

MikeVDS · Post by **MikeVDS** » Fri Jul 13, 2007 12:25 pm

You can also try the torch and screwdriver, hole melting method. If you're left with some excess acrylic, sand or use a Dremel to clean up the hole. Then just use bolts and washers to hold your pieces in place.

Lexan is great too.

gyre · Post by **gyre** » Fri Jul 13, 2007 1:19 pm

I find lexan cracks much worse around holes.
Any holes must be fully chamfered, of course.

What are you actually trying to do?
I would try to glue attachments to the surface myself.

Tubelite has glue made for clear plastics.

MikeVDS · Post by **MikeVDS** » Fri Jul 13, 2007 2:43 pm

I find lexan cracks much worse around holes.

Compared to acrylic? Most of the stuff I've worked with is at least 1/8" to 1/4" thick but I find lexan does great with holes. I used to modify pictures and furniture at an institution (glass was too dangerous and things like TVs needed to be placed behind a clear barrier). I found that the lexan would almost always hold up better than acrylic, holes or not. I also did a couple battlebots and lexan can be some tough stuff.

Dork · Post by **Dork** » Fri Jul 13, 2007 2:50 pm

Lexan does flex more, which I suppose could lead to holes ripping out in certain situations. Otherwise, in my experience you have to work hard to get it to crack. I've used 1/32" through 1/2", cutting/drilling it with all the wrong tools.

1/16" acrylic will crack if you look at it funny.

gyre · Post by **gyre** » Fri Jul 13, 2007 3:30 pm

There are several types of lexan and it can actually be very hard to find true acrylic plexiglas.
Most is mixed with some type of garbage.
I have some real acrylic that has been exposed to sun for many years and still fully clear.

robotland · Post by **robotland** » Fri Jul 13, 2007 4:15 pm

I try to use GOOP or doublestick tape with plastics wherever possible, instead of putting holes in it. Adhesive-backed foam insulation adds a flexible intermediate layer that can absorb some of the stress that can crack plexy bonded directly to metal.
Try boring through plexy with a Dremel, using the end of an abrasive tip. No chunks knocked out, so less chance of chipping and cracking.

Rocket75377 · Post by **Rocket75377** » Fri Jul 13, 2007 6:07 pm

As for the "what am I actually doing," question, it's a cover piece for my bicycle project. The plexiglas is sitting at an angle, covering the front basket. Some have likened it to a windshield, and although that wasn't the original intention, it's a good analogy. I need to fasten it on some way, and a couple of small metal brackets seemed the most obvious and best solution.

I'm kind of stuck with this one piece of plexiglas that I have now, and I'm really hesitant to do anything to it that might damage it. I've gotten the "score and snap" technique down pretty well as far as cutting it goes, but boring holes in it worries me.

My first thought for glue was epoxy, but acrylic seems awfully smooth. Sandpaper first? Would a layer of solvent soften the acrylic for better adhesion, or would it craze it from here to pakistan?

Thanks for the links and advice.

Post by **Eric** » Fri Jul 13, 2007 8:20 pm

I've used "Weldon #16 Solvent Cement" for acrylic and it works great. So far I've had minimum failures, and the failure points are weak spots I know about but don't really care to fix in the design- at least not on the first version.

I don't know if this specific one will work on plexi or not, but I'm sure there's one out there that will. I would bet the good people at Tap Plastics would know.
http://tapplastics.com/
I recommend them so much I should be getting paid.

gyre · Post by **gyre** » Fri Jul 13, 2007 8:21 pm

Polyurethane will cut into and stick to any plastic.
I don't think you need anything too strong for this.
Just make the attachment points large enough.
Tubelite's stuff is pretty much guaranteed to work.
You should always test a scrap or something.
Schnee-Morehead probably has something jazzy.
I'm using one of their one part products to glue aluminum and steel together and I need theft resistance as well as structural strength and a weather seal.
I think epoxy is overkill for what you are doing.

If you can't find out info locally about what you have and what will work, let me know.
We have some experts in the area.
Most plexiglas is usually styrene or some other substitute, especially if it is really flexible.
It is often sold as plexiglas.
True plexiglas is on the expensive side.
I was pricing some recently.

unjonharley · Post by **unjonharley** » Fri Jul 13, 2007 9:21 pm

A quick wipe with acetone (aka finger nail polish remover) will burn the surface.. This makes it rough enough for the goop to grab on.. For small area rub with a qu tip. "Careful"

skibear · Post by **skibear** » Sat Jul 14, 2007 7:32 am

unjonharley wrote:A quick wipe with acetone (aka finger nail polish remover) will burn the surface.l"

Be careful. Acetone is one nasty chemical. It sucke the oil out
of your skin and goes thru thin gloves in about 10 seconds!

Why anyone in ther everloving mind would allow it to be used on
fingernails is beyond me. I would not be supprised if it gets banned
soon as a carcogen.
hth

gyre · Post by **gyre** » Sat Jul 14, 2007 11:55 am

You can get gloves that work.
The osha and other info is about a half inch thick on acetone.
However, so few chemicals are actually tested, acetone may be more dangerous looking simply because it has been researched.
Good ventilation is called for as it is so volatile.
You can make your own carbon filter that can be re-used by heating the carbon or you can use a home made air exchanger.
Or you can just open a window.
Spot ventilation for the user or the work area is the most efficient way to go.

Rocket75377 · Post by **Rocket75377** » Sat Jul 14, 2007 8:30 pm

Gee, the MSDS on acetone is about half an inch thick.

http://www.bu.edu/es/labsafety/ESMSDSs/MSAcetone.html

I've used it before in lab settings, and once to start a fire (Do not judge lest ye be judged. I know what I did.). Nail polish remover is a watered down ethyl acetate mixed with an alcohol, generally isopropanol but sometimes ethanol. Now, don't quote me, but I seem to remember correcting for dilution in the area of 400 PPM of each of the two ingredients. Standard nail polish remover is a lot gentler than lab- or industrial-grade acetone. Still, cautionary statements taken to heart.

Decision thusfar is to mask the area with hundred-mile-an-hour tape, apply a coat of nail polish remover or store bought acetone and allow to dry, sand and epoxy.

Sound good, or is there a better way?

unjonharley · Post by **unjonharley** » Sat Jul 14, 2007 9:09 pm

Good idea to mask area.. Just make a few passes in that area with a corner or a shop towel/rag.. Two second operation.. Less is best.. Your paint store will have the grade you need.. Comes in pints.. I use Millers Paint.. Have used it on some of the finest art in the north west.. It's a matter of touch.. Make a test run.. Also mixed in stripper an can take heat stain out of paited finishes just a few.. Now you know why my brain is fried..