Tech Forum

The cone shaped step drills work very well for round holes in control panels. If you use a drill press it is very easy to chamfer (debur) both sides of the hole using the start of the next step. You can actually drill it half way from each side if the panel is thicker than the step on the drill.

If you want square or rectangular hole; start with the step drill then use a “nibbler” for the desired shape. Home Depot has the Klein #70611B for about $23. There are several other brands available, including heavy duty and power operated nibblers.

A one-inch round hole can be neatly cut with a step-drill.  Many come in sizes that include 1".

Also a chassis punch can be used, although the punches are more expensive. An inexpensive kit of chassis-type punches can be found at Harbor Freight Tools.

Square holes can be cut by drilling inside the corners with a small drill, then cutting between the holes with an emery wheel on a hand rotary tool, such as a Dremel. A file smooths out the cuts. They can also be cut with a "nibbler" if the gauge of the material is thin enough. Nibblers are available from many electronics supply houses that stock tools. RadioShack used to handle them, although I don't know if they still do.

Go to Greenlee punch and you will find your answer. They have been around a long time, but their punches are rather pricey.

While it's virtually impossible to declare a "best" way to do any number of things, I'll share a couple of my favorites.

For cutting round holes in thin materials, it's hard to beat a step drill bit. These are cone shaped cutters that fit in an ordinary drill or drill press and do a great job of cutting or enlarging holes up to about 1.5 inches without mangling the material.

For square holes, I often use a nibbler tool, following up with a file to clean and square up the cut. With a bit of practice you can use the nibbler to cut all sorts of shapes.

The best way to cut a one-inch hole in plastic or metal boxes is to use a chassis punch. Greenlee makes such punches. A one-inch punch is available from Grainger (see www.grainger.com/Grainger/GREENLEE-Round-Knockout-Punch-4A738?Pid=search) as well as many electrical distributors.

Problem is that they're expensive because they're meant for cutting through fairly thick steel. The 1" device from Grainger sells for about $87.

Best bet is to look on eBay for an antique radio chassis punch. At this writing, I found a 1-inch punch offered for under $10 (plus shipping).