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I need to make slots in some aluminium enclosures to accommodate a USB socket like the one shown here.

USB socket

The USB socket is moulded into a 8.9mm by 4.4mm rectangle which protrudes from the rest of the housing. This rectangle needs to fit into the slot I want to cut. It's OK if there's a small gap around the rectangle, so I'm planning to make it 9mm by 5mm. The aluminium is about 2.1mm thick.

There also need to be a couple of holes at either end of the slot for the bolts that hold it in place.

  • The slot is too small to consider using a conventional jigsaw.
  • I could use a hand fret saw, I suppose, but I need to make lots of these, so I'd prefer to find a more efficient way.
  • A router would do the job, but I find they tend to swerve when not properly guided, so the setup for each cut would be tedious. I suppose I could make a jig to keep the router from straying, but that's going to be pretty complicated.
  • I haven't found a nibbler nimble enough for this tiny job.

What would you recommend for this job?

I'm trying to make it look nicer than a round hole like this:

round hole for USB socket

EDIT

Illustration of the Dremel problem - a 24mm disc only cuts to a depth of .9mm when the cut is 9mm long.

Dremmel problem

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  • The jig for a router with a guide collar is just an oversized rectangle cut in a random hunk of wood. You do, however, need a plunge router.
    – Aloysius Defenestrate
    Commented Dec 29, 2022 at 20:17
  • I would use a small file myself and file away the parts that don't look like the hole I want.
    – Harper - Reinstate Monica
    Commented Dec 29, 2022 at 23:28
  • @Harper-ReinstateMonica, that's looking like the most sensible approach to me too. Probably drill to admit a fret saw, then a fret saw to make space for the file, then finish with the file. It's a lot more work than I was hoping for though, especially threading the fret saw blade through the piece : )
    – OutstandingBill
    Commented Dec 30, 2022 at 7:27
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    How many will you make? If it's more than a few you might try asking in Maker forums.
    – jay613
    Commented Dec 30, 2022 at 13:57
  • @jay613, as many as I can sell. No idea how many that will be. Thanks for the suggestion.
    – OutstandingBill
    Commented Dec 31, 2022 at 7:12

2 Answers 2

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As a DIY'er you'll probably find success with a small rotary tool with a cutoff disc and carving/engraving bits.

Drill a hole and use a fret or coping saw.

If the aluminum is soft enough then maybe a couple dozen/hundred passes with a utility knife will cut through it.

If you have a drill press then drill a bunch of holes into the desired shape and then sand down or deburr the sharp parts.

The average CNC machine should have zero trouble cutting that.

If you have some money to spend and plan to do this frequently for a return-on-investment then look into waterjet cutting machines.

Another option could be a laser table but I have no idea about their maximum cutting depth.

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    +1 - But just for the first line - rotary tool, a.k.a., Dremel. Done.
    – manassehkatz-Moving 2 Codidact
    Commented Dec 29, 2022 at 20:28
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    @manassehkatz-Moving2Codidact Thanks but that's OP's call. What if they own a drill press but not a rotary tool and wish to avoid spending money?
    – MonkeyZeus
    Commented Dec 29, 2022 at 20:34
  • I don't own a Dremel or a drill press. I can't see how a Dremel would work for me in a 9mm long cut unless there are some very small discs avaiable. I sketched it out in a CAD tool. If my calculations are good, then with a 24mm disc, by the time the cut is 9mm long it'd only be 0.9mm deep. I've illustrated this in the question.
    – OutstandingBill
    Commented Dec 30, 2022 at 7:10
  • I beg your pardon - I skipped the "engraving bit" part. I think I'm dyslexic. Yes, that might do the job, but it'd need a preternaturally steady hand, I imagine. Do you find the rotating bit tries to pull off to one side, according to the direction of turn?
    – OutstandingBill
    Commented Dec 30, 2022 at 7:24
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    The cutting bits do tend to "pull' - so cut from the waste side of the line, and practice.
    – Solar Mike
    Commented Dec 30, 2022 at 11:01
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I happen to have a plunge router. I had considered making a jig to hold the work piece and guide the router. As I first imagined it, it was quite complicated, but a simpler idea occurred to me today.

This jig has a backbone (shown in the photo with my thumb on it) which goes under a broad piece of wood I'm calling the router table.

end view showing backbone

The backbone and work piece (white, partially hidden in the next photo) are clamped together in a suitable vice. The position of the backbone under the router table can be adjusted and secured with the bolts at either end. There are end stops to limit side to side movement, and guide rails to prevent front to back movement.

work piece clamped in place

The router's own guide rail allows the side to side travel to be adjusted.

router positioned ready to cut

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