Cutting holes in .25" Acrylic

[parth]

I got some acrylic for a new case mod, and I need to cut some simple, but small designs into the 1/4" sheet acrylic for various reasons. An example cut would be a 1"x1" square hole.

The only tools I have that could be helpful, as far as I know, are a dremel with a set of cut-off wheels, and a drill. The dremel+cut off wheel should be theoretically perfect for this, but the problem is that I have to angle the dremel so that the cut-off wheel will contact the surface of the sheet (do you know what I mean or should I explain more?) Then, when I try to cut through the sheet, I have to increase the angle further, so I end up with a cut that's the right size on one side but too small on the other because I can't just cut lower the dremel to cut cleanly. It's hard to explain - do you guys get what I'm saying? Anyways, then to get the cut the way I want it, I have to get out a burr which takes forever to go through the acrylic and manually grind down the edges on the side where the cut is too small.

What are your suggestions on how I can solve this problem? A scroll saw would be ideal (I would drill a small hole, put the saw through, and cut), but I don't have the kind of money to buy one or will I ever use it after this project, in all likelihood. A jigsaw, too, might work but is there anything cheaper? Thanks.

EDIT: I keep seeing Plexiglass Cutters like this one (http://makezine.com/pub/tool/Plexiglass_cutter) being suggested for people who are cutting large sheets into small ones, but would it work for cutting holes in plexiglass?

[Chewbenator]

I don't think it would take all that long to simply take a file and make the edge flush going in from the larger side.

[widefault]

I prefer a drill and a good set of files. Use the drill to remove the bulk of the material then clean up with the files. The Dremel is okay for some larger cuts, but for anything small I always worry about coming out of the cut and marking up the rest of the piece.

[Navig]

If its in the range of a 1in hole, your best tool (and cheapets) would be a hand drill and a holesaw. If you want varying hole sizes, you can get cheap hole saw kits from costco ($20) which includes the arbor and various sizes. If you only want one size hole, you can pick up an individual hole saw from your local hardware store. The price will range from about $8 to $35 for a 4.5in holesaw (for 120mm fans).

If you have access to a drill press, hands down the tool you want is a adjustable circle hole cutter. (http://www.amazon.com/Anytime-Tools-Adjustable-CIRCLE-CUTTER/dp/B000I39OKQ)

Dremel is extremely difficult to get a decent hole as you have a strong tendency to melt the plastic, and you spend twice the time trying to finish the edges.

navig

[parth]

Good idea. I think I'll use the Dremel to get the rough surface down and then just file it to perfection. Fortunately, the acrylic I bought was thermoplastic, so it doesn't melt. I like the drilling idea too, but frankly it seems like it would take forever (I'll try it once and see how it goes). I was thinking of getting a right hand attachment for the dremel, but that would cost more and probably wouldn't give me the precision hand filing does.

[parth]

If its in the range of a 1in hole, your best tool (and cheapets) would be a hand drill and a holesaw. If you want varying hole sizes, you can get cheap hole saw kits from costco ($20) which includes the arbor and various sizes. If you only want one size hole, you can pick up an individual hole saw from your local hardware store. The price will range from about $8 to $35 for a 4.5in holesaw (for 120mm fans).

If you have access to a drill press, hands down the tool you want is a adjustable circle hole cutter. (http://www.amazon.com/Anytime-Tools-Adjustable-CIRCLE-CUTTER/dp/B000I39OKQ)

Dremel is extremely difficult to get a decent hole as you have a strong tendency to melt the plastic, and you spend twice the time trying to finish the edges.

navig

The hole saw would be a great idea but the problem is that I have to cut all sorts of weird shapes into the acrylic, like rectangles and triangles. As far as I know the hole saw can only do circles.

Also, as I mentioned the acrylic I have seems to be thermally resistant, because it says "thermo" and it doesnt melt when I cut it.

[Navig]

Sorry misread your original post. For short shapes, dremel will work fine, short of a scrollsaw. Just use a rough flat file to get the edges flat, then chase it with 400 grit wet dry. If you want a completely clear edge, 400-800-1000 and some novus plastic polish or 3m rubbing compound.


Mask a LOT, one stray sweep with a dremel and you've got a big scratch.

navig

[parth]

Sorry misread your original post. For short shapes, dremel will work fine, short of a scrollsaw. Just use a rough flat file to get the edges flat, then chase it with 400 grit wet dry. If you want a completely clear edge, 400-800-1000 and some novus plastic polish or 3m rubbing compound.


Mask a LOT, one stray sweep with a dremel and you've got a big scratch.

navig

I'll definitely try sanding to get that smooth & clear edge. Also, regarding cutting, I have about 1/16" of cardboard-like paper on there (it came on the acrylic), so I'm protected against scratches.

Well, I'm off to home depot tomorrow for some files and a plexiglass cutter (it's cheap, so I'll see how it works and post the results).

[jimmyz]

try a coping saw, it works like a jigsaw but manually powered. you can wrap tape around a blade and use it without the frame if needed. it's tedious work and you will need to drill an access hole to get the blade through.

[Navig]

The plexiglass cutter is for scoring, so it'll only work for edges that you can bend at. I've found cheap acrylic (ie home depot), it works alright if you are meticulous about clamping straight edges, even then the breaks will stray from the score occasionally.

[parth]

I just got a file set from HD, and let me tell you it is going to take forever. Like 1 hour to take off 1mm from the acrylic. Is that supposed to happen? I'm even using the rasp that came with the set!

[Navig]

What is that you are trying to do? Pics would be nice. Files and rasps are for edge clean up.

Example from start to finish. Let's say you want to make a 1" side square in the middle of a plexi piece. First mask everything off. Then make cuts just a hair inside of your lines with a dremel and a fiber reinforced cut off wheel. This will cut out a hole, but the edges will often be rough and bezeled (on account of the cutting wheel often not being perfectly perpendicular to the surface as you've mentioned). I make as much of the edges perpendicular with the dremel sanding drum, but this can't reach into the corners. You can gently scrape at the corners a little bit with the cut off wheel. Next I use the file to further straighten the cuts and the corners. Once the edges are all true, but still rough, then I hit it with 220 grit wet dry sandpaper under some running water. Chase it with 600 grit. Now it'll have a dull finish. Novus 3 will give a little wet look. Or 1000, maybe 1500, Novus 2 or 3m rubbing compound to give a completely water clear look.


navig

[ginnz]

for cutting plexi, a slow speed jigsaw works the best, or a scroll saw, anything high speed will just "melt" the plexi/acrylic back together.

[parth]

Thanks for the replies guys. I've been busy today with a motherboard RMA (my main system died 2 weeks ago, and I finally got it working again), but hopefully I can post some pics tomorrow (hopefully they'll be good quality, but no guarantee because my stupid 5 megapixel camera doesn't have manual focus).

[parth]

By the way Navig, I have to say your cases are really, really nice. I would be happy if this project turned out 10% as good.

[teyber]

i know this is for metal, but if you put some oil like 3 in 1 oil on the plexi before cutting, it acts as a lub ricant and is better.

and to avoid crackign yoru acrilic, don't force the blade through the material like with wood or sometimes metal, i like to just let it sit near the top and actually kinda melt or shred away the plexi. I have never cracked any plexi this way, nor do i burn it and have to sand much.

good luck!

[parth]

Ok, so I have some pics to show what I've been doing. First, however, some background: I'm making this case to house a watercooling setup - it will have the pump, radiator, a t-line, and should also be able to house some fans in the far future, but as you can tell I'm currently well occupied just trying to make the case out of .25" Acrylic.

Also, this is the first time I've used any power tools since 8th grade Woodshop, so forgive the terrible workmanship. At least I'm getting better!

Here's the back panel, which is what I've been working on currently, since it's alright if it's somewhat ugly.

http://farm2.static.flickr.com/1225/772482196_9fe5013c4b_b.jpg

The holes that I'm currently making will be covered up by metal (the
rectangular ones will be covered by plate metal, and the smaller ones are screwholes), so it's not absolutely critical that they look great - I'll do the highly visible parts later when I have better workmanship. By the way, I'm cutting at the bold lines.

Here's the back:

http://farm2.static.flickr.com/1132/772480444_eb0845886f_b.jpg

As you can see, I didn't do too well with the first rectangle - one side is almost acceptable, but the other side is just terrible. I've given up on trying to improve it for now, and I'm going to try to cut the 2nd small rectangle. The reason it looks so bad is because I suck with the engraving bit/burr (below), which I have now abandoned for better initial cuts with the dremel and files. That bit is especially bad because it exaggerates extremities, rather than smoothing them out like I want - it has a tendency to get stuck in "valleys", places where the acrylic is lower than usual, and then it burrows even deeper down, accentuating the problem.

http://farm2.static.flickr.com/1280/772485864_33c905fde8_b.jpg

By the way, here is the rotary tool I'm working with, and all the attachments I have (I got it for $6 + $20 shipping off of eBay).

http://farm2.static.flickr.com/1039/772487814_da33f4b16a_b.jpg
http://farm2.static.flickr.com/1292/772489360_ab35ed5eca_b.jpg

As you can see it's very low quality (the rotary tool is 3.6V), but I pretty much had no choice: I have a $300 budget for all materials, tools (the only thing I had before this was a drill), and watercooling equipment. The watercooling equipment cost $210, so you can see my dilemma.

So let me go through what my plan is for the second rectangle.

Step 1: Cut the long sides(In progress)

http://farm2.static.flickr.com/1081/772484088_a53b61e264_b.jpg

First I created a shallow groove on both the top and the bottom so that my cut of wheel can rest inside without fear of getting out of control and scratching everything up (it's so weak that it won't cut through the brown paper you see without me forcing it, so fortunately scratches aren't a big worry).

Then I simply cut through the acrylic until the cut-off wheel reaches the other side (I put a stack of papers so that the wheel wouldn't have to cut the cutting board below).

Here are some more pics:

After more cutting:
http://farm2.static.flickr.com/1216/772475024_be7f2f0013_b.jpg
Here we see some acrylic powder (for some reason, my acrylic doesn't seem to melt, but rather turns into a powder when I'm cutting):
http://farm2.static.flickr.com/1032/772473344_b16fb48a97_b.jpg
And here we see the bezel that results from me having to angle the dremel to cut deeper:
http://farm2.static.flickr.com/1067/772476886_aef9cf5605_b.jpg

The steps I'm planning to do:

Step 2: Use a drill and a large bit to cut through the short sides (the cut-off wheel is too large for it, and even if it was small enough it wouln't be able to cut all the way through the .25" thick acrylic)

Step 3: File everything down

Step 4: Sand to perfection, if necessary

So what do you guys think? Does that illuminate my project a bit more?

(Btw, thanks for all the help so far)