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View Full Version : Advice on punching holes in Plex



strider
04-08-2009, 10:35 PM
Alright, I have a problem for which I really need some help, and I know it's to be found somewhere within this group.
I need to punch some holes in a Plexiglass panel. Normally not an issue, there are a variety of ways to accomplish that mission. But here's the rub, it's installed and in place, I can't remove it to mount on the mill and bore the holes to size. There are obstructions, some of which could be removed, but it eliminates some methods. I'll have to use a hand drill to accomplish this job. Sort of eliminates the crappy circle cutter and some other stuff.
The Plex is 3/16" thick. The holes can't be undersized but can be slightly oversized, +.050-.075 would not be an issue. There will be several holes but there are 5 that I'm puzzling over. All are, unfortunately, varying sizes, and the sizes are such that typical fractional sized hole saws won't work. As an example, the largest is 2.15", +.050-.075. The smallest 1.3" (could hole saw that one, maybe).
I'm open to suggestions. Have to be up in six hours so I'm going to go and sleep on it and hope the Solution Fairy comes during the night.

Duffy
04-08-2009, 10:44 PM
Not either quick or easy, but will work:- a small router with a pattern-following bit and some templates cut from 1/4" thick whatever. You can make the templates on your mill to the precise oversize to allow for the bit. I mean the type of bit that has a bearing at the TOP not the bottom. I think you can get them down to 3/8" diameter.

TGTool
04-08-2009, 10:48 PM
Hmm. I'd be inclined to make up a circle template from plywood or other plexiglass (inside hole), then stick it to the target piece with double side tape and use a router or dremel tool to do the hole. You can get follower bushings for the router, but I've done wood by setting the toolbit depth so the cutting edges are in the material and the smooth shank is the template follower.

There's no danger of it getting away or going oversize since it's limited to the hole size in the template minus pilot diameter.

<edit> Ah, must be great minds thinking alike. Couldn't be "fools seldom differ" could it?

doctor demo
04-08-2009, 10:53 PM
I would try getting some hole saw blades and re-set the teeth so they either get larger than original or smaller if You get a bit that is "" just barely "" to large. If that doesn't work , You can make Your own the size needed.

On first reading the title , I thought You wanted to "punch" the holes. I have never tried that....but I'm going to now just to see if it works without shattering:eek: .

Steve

Duffy
04-08-2009, 11:00 PM
NEVER TG! Duffy

barts
04-08-2009, 11:02 PM
Hmmm...

0) You could find metric Forstner bits, or turn some fractional ones down
to the right diameter.
1) You could likely just turn down some inexpensive hole saws w/ a carbide bit to the right diameter.
2) You could make custom hole saw blanks and file in some teeth.
3) Use an adjustable wood boring bit

- Bart

MaxxLagg
04-08-2009, 11:50 PM
I'd go the Dremel and template route. I have a router attachment that my Dremel fits in that would work sweet for that type of job. Mine is about 10 years old and looks different then this one, but you get the idea. You could probably make one. I always use 1/8 carbide endmills in mine.

http://www.utopiatools.com/-strse-269/Dremel-Router-Attachment/Detail.bok

Evan
04-08-2009, 11:56 PM
I'd let somebody else do it.

macona
04-09-2009, 01:13 AM
Laser Cutter! Tried cutting acrylic for the first time on our epilog and its pretty amazing. Most plastics shops can do it for you.

Paul Alciatore
04-09-2009, 02:53 AM
I would recommend a step drill. They make excellent holes in plastic. Since you have a nice generous tolerance on the plus side, getting the right diameter should be no problem. They come in 1/16" and 1mm steps. Just don't run them too fast or the plexiglass may melt.

Your Old Dog
04-09-2009, 06:17 AM
I would back it up with a pine board so it won't flex and grab whatever you choose to cut it with.

I'd also use vegetable oil from the grocery store as a lubricant with whatever you choose to cut it with.

Let us know how you did it and how well it worked. I need to cut a few large holes in my Harley windshield to let the bugs through, kinda like, what's a picnic without ants !!

strider
04-09-2009, 08:25 AM
I guess I was suffering from the "forest for the trees" syndrome. First, I'm going to try routing them out with templates and a Dremel. I can shape the outside of the templates to get around my obstructions and eliminate some work that way. If that doesn't work to my satisfaction I'll try the other suggestions.
I can't believe I didn't think of that, of course after having finally acquired metal machining capability I overlook the my old woodworking methods. In the past I've done a lot of plastic, all with woodworking tools, after all, plastic is just artificial wood.
I'll let you know how it turns out.
Thanks guys.

john hobdeclipe
04-09-2009, 08:50 AM
My experience with hole saws in acrylic sheet is that they get too hot and melt the acrylic, which then just rolls up, jams the teeth, and leaves a mess.

My recommendation would be to use a drill bit / counterbore. The counterbore can have two, three or four teeth. If you can't find counterbores in the needed sizes, either modify the ones you can find, or make them (easy enough if you have a lathe and mill, I just made one earlier this week.) If it's a one use deal, you probably won't even need to harden them.

MikeHenry
04-11-2009, 02:35 PM
It might be interesting to try a Greenfield hole punch on some scrap acrylic.

Mike

nheng
04-11-2009, 04:08 PM
I suppose speed may be an issue here but I'd go with a router, guide bearing (like the panel edging types) and a template that sits off the surface a tad, clamped outside the area of interest. Den

JRouche
04-11-2009, 11:28 PM
I like the template and router deal. I have used carbide end mills in routers with great success. And for tight spaces the rotozip saw with a foot makes a nice router, variable speed and lots of power. You can just double side tape the template to the plastic. JR

jacampb2
04-12-2009, 07:49 AM
I would recommend that you check out Onsrud.com. They specialize in plastic machining. Their catalog has drills for acylic, as well as most other types of plastic. I have been buying and using their routing bits for acrylic with excellent luck for the last month or so. They have a much better finish in acrylic than any other router bit or EM I have tried. I have not had any experience with their drills yet though.

Their prices are about average for a high quality cutter, so I assume it will be reasonable for drills. I can check if you want.

Later,
Jason