How to cut square/triangle holes in ABS project boxes

Hi All,

This is a mini-instructable as it will be useful for some other instructables that I will post which require square holes in ABS! I thought I would post how I do it - as it took me a VERY long time to find a satisfactory solution. I am still experimenting with this method but so far it seems to be the fastest way to cut into plastic for making square holes. I have found so far that the smaller the hole the narrow your blade needs to be to avoid plastic bubbling over the line - with larger holes it is not so much of an issue. ( Thanks to Iliah Borg for pointing me in this direction )

Step 1 Tools Needed

You will need the Gascat 75P gas soldering iron OR something similar or with similar tips. This kit has 5 tips. A soldering tip, a hot knife tip, a flame tip, a hot air tip and a deflector tip. The particular tip we are interested in is the hot knife tip.

The other item you will need is some kind of grinding kit. I recommend the Rotary Craft mini rotary tool. This contains a selection of grinding tools. I bought a grinding/cutting addon for mine. This is actually what I attempted to use to cut the square holes to start with but it didnt work out - very hard to control the circular blades and pretty useless for small holes. Do a search on ebay for them.

The grinder I use is shown below. You can see two tips. The one attached to the rotary tool I used to polish up the metal after grinding. The pink tool is what I used for grinding - worked very well.

Comments

[tilmen]

Hello, once I've seen this image in the net.Maybe it helps.

[GTechno13]

I've also been looking for a good solution for square holes. Something just occurred to me. What if a square (hollow center) hot air rework nozzle was sharpened at the (inner) edges and was heated up and pressed through the plastic. The square would need to be the exact size or smaller than the desired hole. A method of quickly removing the nozzle may be needed so air isn't trying to blow onto the center of the hole as rework air cannot be immediately stopped.
I'm in the market for a rework machine so this may be interesting to try.

Also
It would be nice if there were some pictures of the actual box being cut.

[mothflavour2]

I usually just drill a hole and file the corners down. But that's a good technique if I ever need to make a slot. (although I'd probably just torch an x-acto knife blade and melt through)

[junits15]

that will warp the blade from the extreme heat

[T3Hprogrammer]

Is it possible to cut the exact right shape holes by heating up the (metal) part you want to insert? I'm thinking D-sub connectors (plastic removed)

[AlphA303]

Thanks for the post! This is way better than my technique of drilling big gross holes and filing them into the shapes I need.

[nickjohnson]

I've always used a combination of these three: (1) A drill press, possibly with a router bit, (2) A coping saw, and (3) A nibbling tool. This has always worked pretty well for me.

[_soapy_]

I've found my gas torch to be quite useful. I hadn't though about filing it down, but it is obivious when you think about it. If doing a large hole, start your cut in the middle, and move to the edge, then go around. It leaves a better finish.

[theRIAA]

nice lightbox