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Tool Tips -- rectangular holes
Jon Titus, KZ1G <tituskz1g@...>
Perhaps a bit off topic, but here goes...
In a recent post, looking for a 40M QRP SSB kit, Fred (K3TXW) explained, "...I have problems making a rectangular hole in a piece of aluminum of exactly the right size, with the edges exactly parallel to the edges of the case. I inevitably make the opening too big or slightly wavy. The result screams "homebrew carelessness" though I'm not careless. Maybe there is a rectangular punch or something to do this right, but I don't have such a tool; I use a set of files."
In addition to files for work on front panel fabrication, I recommend an electronics shop include:
1. A drill press with a chuck that will accept 0.50-in.-diameter bits. Harbor Freight sells a couple of bench-top units for under $100. Put a magnet on the base as a place to keep the chuck wrench. (It's usually best to clamp work to the drill press table.) Once you have a drill press you'll find many other jobs for it.
2. A good set of sharp drill bits. Bits with a titanium nitride coating remain sharp for a long time.
3. A step drill bit. I use an Irwin Tools Unibit 3/16-Inch to 7/8-Inch Step-Drill Bit with a 3/8-Inch shank. Great tool when you need to make larger holes for controls or to start a rectangular cutout.
4. An Adel-brand metal nibbler. They show up on Ebay. Or buy a new one at https://www.adelnibbler.com. I've used one since I was a teenager and couldn't work on chassis or panels without it.
Lay out your hole with masking tape around the outside. To make a rectangular hole (see attached image) I use a step bit and smaller bits to make round holes that remove a lot of metal. Just don't get too close to the rectangle's edges. Next I use the nibbler to remove remaining metal close to, but not at, the rectangle edges. Finally I clamp the panel or chassis in a bench vise so an edge of the hole aligns with the top of the vise jaws. File away any remaining metal until the edge is parallel with the vise jaws.
Jon Titus, KZ1G
Herriman, UT USA