/diy/ - Do It Yourself

[Anonymous No.555839]

Hello, I just needed some advice on cutting acrylic. I've looked up many helpful videos on youtube and other sites on how to cut, weld, drill and polish acrylic but not many helped in deciding what kind of drill bit to use. I know for most acrylics it should have a large number of Teeth Per Inch (TPI) on the blade. I'm not sure if I have acrylic/plastic blades/drill bits but I have wood, metal and glass ones (though wood accessories are useless for acrylic purposes). Does anyone how how much TPI is needed for hole saw blades? Or even jigsaw blades? Thanks.

[Anonymous No.555842]

acrylic is a pain in the ass to drill or cut. I dont think i'd even bother to use a hole saw on it, it'll more than likely just crack the whole piece rather than drilling a hole. The stuff is really brittle, i remember i made a small box out of it, drilled one hole with just a regular bit and the torque of the drill was enough to snap the whole thing in half rather than drill a hole.

It also melts easily, so any time you use anything like a drill or a saw you have to go extremely slow or the acrylic will just start melting, and it wont cut hardly at all anymore and it'll jam up your saw blade or drill bit with all kinds of gunk.

[Anonymous No.555843]

doesnt matter, use metal ones, tpi doesnt matter, just drill slower to match (high drill speed slowly push)

[Anonymous No.555846]

I used a dremel with a cutting wheel and it worked pretty well.

[Anonymous No.555847]

>>555842
>>555843
They are only A4 sheets of acrylic at 3mm deep (about 1/20 inch). I have been told to drill slower or the drill bit will latch on the acrylic and crack it. I guess metal should be fine I think it was 32 TPI. As for the melting, it should be easy to get rid of. As soon as the acrylic is melting, peel it off before it hardens or I've been told to use water to cool it to prevent that. Thanks though.

[Anonymous No.555848]

The difficulty with drilling or cutting acrylic is how brittle it is. Because of that you can't center-punch holes prior to drilling, which means the drill bit will want to walk away from where you are trying to drill.

1. I would advise ONLY using a drillpress or mill for drilling acrylic. A handheld drill isn't going to work straight enough and you'll have less control over the downward force and centering where you want to drill.
2. You need to back whatever you are drilling with wood.
3. Use as little downward force as possible.
4. Use dish soap and water as your cutting oil.
5. You can use standard drill bits smaller than 1/4-inch but they need to be SHARP.
6. Forstner (brad point) drill bits work the best though.
7. You can use wood-boring drill bits if you're careful.
8. Use RPMs no higher than 1200.

As for blades it really depends on the tool you are using. Any scroll saw blade will work so long as you have the air nozzle pointed at the cutting area.
If there are plywood/OBS or wood "smooth-cut" specific blades available for the tool you are using those will work best. Using the right blade is especially important when cutting plastic with a table saw.
You basically can't use the more aggressive lower tooth count blades, and you also cannot use abrasive blades. Both will either get stuck, cause excessive melting, or crack/chip the edges of the cut.

I haven't tried using hole saws to cut acrylic because I prefer doing that kind of cut with a scroll saw which is easier to control and more predictable. I can't imagine the standard tooth count for those even working. A metal specific hole saw with a higher tooth count is more likely to work.

[Anonymous No.555849]

>>555846
I have been looking into dremel tools but I wouldn't be using it that much, so I wouldn't invest in it. I do have other tools though, just not dremel drill bits.

[Anonymous No.555852]

>>555848
Alright, I do have a drill press. How about for jigsaws? Can I use that to cut straight lines (along a guideline)? I think I have these cobalt or tungsten carbide blades or drill bits, mainly for metal working. They're pretty fine compared to the wood ones.

Also are glass cutting and adjustable drill bits good for acrylic? Have you used them? (In pic)

[Anonymous No.555851]

>>555848
Cont'd

As for welding you will be best served by using Weld-On solvent adhesives. Weld-On #3 and #4 offer the same performance in only slightly different viscosities.
Some people prefer to use MEK (Methyl Ethyl Keytone) as a solvent adhesive but it's some really nasty shit and shouldn't be used indoors.

For polishing you can approach it several ways.
1. Use your solvent adhesive to remelt/wet the roughest areas, particularly cut edges.
2. Use sandpaper working up towards 1200 grit then finish with wet sanding and a plastics polish like Novus brand.
3. Those in a hurry tend to just use a butane torch to flame polish but I don't personally have any practice with that.

[Anonymous No.555854]

>>555851
I think I have an equivalent one of #16 acrylic glue, I've seen it's pretty thick.

I'm not too worried about polishing, I'm not making a display case or anything, it's just a small greenhouse. Using the solvent isn't actually a good method, it's really messy and spills can ruin the work. Fine sandpaper is fine. Not that I have one but a buffing machine or router can really smooth it out, especially if you have a laser cut one. Flame polishing looks really nice but you can't reattach any other pieces or even put the acrylic glue on it or else it will crack. Thanks for all this info though.

[Anonymous No.555855]

>>555852
>>How about for jigsaws?
Wood Smooth-Cut blades.
>>Can I use that to cut straight lines (along a guideline)?
Yes. You might want to tape your acrylic down to a sheet of thin plywood to avoid bending it when you're pushing the jigsaw onto it.
>> I think I have these cobalt or tungsten carbide blades or drill bits, mainly for metal working.
You don't need coated or even carbide bits. They just can't be the ultra cheap and really dull Chinese bits you buy from harbor freight. The sharpness of the cutting edge is the only important factor.
If you need to drill really precisely drill a centering pilot hole with a 1/16th or 1/8th drill bit. Then drill it out with your intended drill bit.

>>Also are glass cutting
I've never tried using those.
>>and adjustable drill bits good for acrylic? Have you used them? (In pic)
I've only used those on a mill because trying to control the depth of cut using those on a drill press is difficult. Where as on a mill you can crank the table up a couple thousandths at a time.

[Anonymous No.555856]

>>555855
Alright cool, thanks.

[anus presley No.555859]

one way to avoid the melting nightmare when cutting acrylic is to use a scratching blade, and then snapping the piece. i'm guessing there are youtube videos showing how to do this. i usually use 5mm sheets, and will scratch a line into it of 1mm depth. at that depth, i've never had a sheet not break perfectly.

[Anonymous No.555861]

another thing i've found is that acrylic warps very easily.

Even if you cut it or drill it, the heat and the torque may not be enough to melt it or crack it, but it could very well warp the pieces 1/16" or so without you really noticing until you go to assemble the thing.

Thats why i always avoid trying to machine the stuff if i can. Just scoring it and cracking it gives probably the cleanest cuts you'll get without warping it.

[Anonymous No.555888]

>>555839
There are drillbits and saw blades made specifically for working with acrylic plastics (plexiglass). Ironically enough a plastics store (e.g., Tap Plastics) will sell those kinds of tools.

[Anonymous No.555894]

>>555859
>>555861
Could I use a scalpel blade or a box cutter to do this if I don't have a scoring knife?

[Anonymous No.556040]

Cutting acrylic is such a pain, I just chuck it in the oven then cut it with scissors. Unfortunately that warps and shrinks it terribly.

I wish I had a 3D printer so I wouldn't have to go through this bullshit.

[Anonymous No.556049]

>>555894

Depends on the thickness. You'll have trouble scoring them deep enough if it's a thicker piece, but you should be okay if it's under 1/8" or so.

>>556040

If you're screwing up the optical qualities of acrylic by doing that (the only reason acrylic is even used most of the time) why are you using acrylic at all? You could just use ABS or even just polyethylene. Or, if you DO need it to be transparent and it doesn't need to be out in the sun all the time, polycarbonate.

[Anonymous No.556061]

>>556049
Local hardware store doesn't stock ABS. Stuck with shitty acrylic.

[Anonymous No.556292]

>>556061

Fuck that shit, son, order some up. I dunno about your hardware store, but the last time I looked at the plexiglass in Home Depot/Lowes, they were overpriced by easily double, handily surpassing the extra cost of shipping for even just one sheet.

[Anonymous No.556448]

>>556292
What's the rate of plexiglass or acrylic that you buy?

[Anonymous No.556525]

>>555894
>Could I use a scalpel blade or a box cutter to do this if I don't have a scoring knife?

A scoring knife has a 'bit' on the cutting area much like a plow. It 'plows' the plastic up into a curl much like a plane on wood.

An ice-pick, a scratch awl or nail held vertically would work better than a scalpel which would be trying to cut it instead of scratching it. The score line is just a very deep scratch.

If you really want to use a scalpel, use a #11 blade. Hold it vertically (handle pointing straight up) and pull it toward you with the back of the blade facing you. It sounds backwards but it works best this way.