Re: Tool Tips -- rectangular holes

Bill Cromwell
 

Hi John,

I hide imperfections around a rectangular hole in the front panel with a bezel. Those will hide a lot of sins. They are also easier to fabricate with straight, clean edges. Riy=ugh edges that might show a little on internal panels of chassis - who cares.

Your use of the bench vise to keep the edge straight during filing is good but will eventually damage the vise. I use a sacrificial piece of steel like a piece of angle iron clamped up along with the workpiece. In woodworking we call that a "fence".

73,

Bill KU8H

On 10/30/2018 11:50 AM, Jon Titus, KZ1G wrote:
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
--
bark less - wag more

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