Has anyone tried making rectangulr holes in ABD plastic boxes using a hot cutting knife. All the posts I've see use drills and gring tools. Seems the hot knife would be easier.

 

I typically use a small drill hole on the 4 corners and a jewelers saw to connect them. Then a bit of file/sanding to smooth the cut. Or avoid having to do a square cutout.

 

The plastic could be cut with a hot knife, but it may generate toxic fumes in the process.

 

I have used a fine rotary saw blade in a Dremel, finished off with fine flat file.

 

You didn't say what size or how many holes you need to make. You could do it using Greenlee punches if they have the right size. https://www.greenlee.com/us/en/rectangular-punches--dies

 

I have a Greenlee set, but they tend to splinter the box if not exceedingly careful.

 

I'm lazy and use round rocker switches

 

I'm lazy and use round rocker switches

Looks a little funny used on 2 line displays though!

 

We had a real nice Greenlee set at work. Great for doing 1/8 and 1/4 DIN panel cutouts along with the hydraulic pump. Nice stuff but expensive tools. Since retiring I use a hand nibbler or my Dremel with a cutoff wheel. Using the latter have to make sure I don't melt the plastic. The Greenlee was great for doing 19" rack mount panels but those were expensive over 10 years ago.

Ron

 

I would print the box with the holes left out.

 

Many many years ago I saw something where someone took an old TV antenna radial and formed it into a rectangle or square, then filed the inside edge to form a wedge with the outside surface being continuously straight, then heat it up with a torch, then push the hot metal through the project box to cut said forms. Thought about doing that, but the process is involved enough to dissuade me from going that route. Then

The plastic could be cut with a hot knife, but it may generate toxic fumes in the process.

Hadn't thought of that before; and it's an excellent point. I had some plastic sticks from something, the sort of which I don't know the material. When I heated it with a torch I immediately began coughing and choking from the fumes it gave off. Not "Smoke" - "FUMES". It didn't take me long to stop messing with that poisonous stuff. Don't remember what the reason for melting them were, but it was most definitely NOT worth the danger of toxic fumes. Maybe that's what stunted my growth.

 

I now have a nibbler tool. Aluminum, copper, tin and even thin enough to fit into the jaws - plastic. Takes a little wrist action, but it gets it done.

 

Has anyone tried making rectangulr holes in ABD plastic boxes using a hot cutting knife. All the posts I've see use drills and gring tools. Seems the hot knife would be easier.

This used to be a real PITA until I learned how to use 3D design software. Now I can design a box and cutouts anyway I want.
You might do the same...

 

I have a Greenlee set, but they tend to splinter the box if not exceedingly careful.

For using chassis punches on ABS boxes and lucite panels I take two pieces of scrap aluminum or steel sheet larger than the hole I want, which are pre-drilled with the punch bolt hole. Then I drill the bolt hole in the plastic. Then line up the holes and glue them together with cyanoacrylate cement applied inside the area that will be punched out.

The metal supports the plastic so the punch makes a clean whole. I have only found this useful for special punches like D holes or indexed holes for controls because it is a fair amount of work.

The other alternative are old school nibbling pliers. Amazingly, the ones I have used for so long are still available! They make a clean, straight cut and have a 1/16" capacity. It's perfect for aluminum but only for some plastics.

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The other alternative are old school nibbling pliers.

I now have a nibbler tool.

 

We had a real nice Greenlee set at work. Great for doing 1/8 and 1/4 DIN panel cutouts along with the hydraulic pump. Nice stuff but expensive tools.

You can get Greenlee punches for a lot of different devices, a long while ago I purchased the ones for DB9 terminal socket when I had many to do.
These are the rotary blades I use for square plastic holes, you can also get just the saw blades alone. available on Amazon,

 

I now have a nibbler tool. Aluminum, copper, tin and even thin enough to fit into the jaws - plastic. Takes a little wrist action, but it gets it done.

I didn't see your post before I made mine. I bought mine about 45 years ago in a Radio Shack store. I just ordered one from Amazon when I saw the old RS tool was available.

 

If you order a Polycarbonate pr PC/ABS project box, the material is much more ductile than "acrylic" (Lucite, Plexiglas, etc brand names) - you'll have much more luck with Greenlee punches.

 

A plastics blade for a jigsaw along with a file and sandpaper usually gets things done for me. I usually drill somewhere in the middle of each side to get the corners square. Clamp on a piece of square aluminum for a straight edge and it's even better.

 

In the past I've used a soldering iron to melt holes in plastic panels, but it doesn't smell good. A sabre saw or jigsaw is probably the quickest way to cut rectangular holes; you can often find those used for under $10. Protect the surface with masking tape, mark the holes, then go over the hole outline with a knife and straightedge. Drill a starting hole then saw the hole a little undersize and finish to the scribed outline with files. With the right blades you can cut holes in steel panels that look like they were done by a robot.
Helpful accessories would be a combination square for marking hole locations and scribing straight lines, and a Quick-Grip clamp for holding the panel/box steady while you control the saw.