How to cut a square in a blank panel with minimal tools?

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Just discovered a chassis I bought quite a while back came with an IEC plug but the back panel has no cutout. A bit too much time has passed to contact the Chinese seller and the particular model doesn’t seem to be available any longer.

Don’t have access to water jet or CNC equipment, can someone enlighten me on the best method to cut a square for an IEC socket in a blank panel?

I have a drill and metal files and so on, but clean, professional looking results is not my strong suit.

How can I do this without making a mangled parallelogram?

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This is a nightmare for many people. You can buy a stamp, but it's silly money. There are iec sockets designed for round holes, which can be a lot easier to mount. Your immediate fix is to drill, saw, and file. Making sure you saw the hole too small, and have a lot of filing to do. A gap would be terrible. The flange on some of these is under 2mm, so there is little room for accidents.
 
How can I do this without making a mangled parallelogram?
Nibbler tool -- about $7 -- I think you can find it at Parts Express etc.

You can also do it by drilling a series of small holes within the outline of the IEC socket, put the panel on a piece of wood and knock it out with a punch -- then file. The IEC power connectors I have used have 6 sides so you won't find a Greenlee punch for less than a few hundred dollars.
 
I once had a few to do. So I first fitted one though a plastic panel that was easy to shape with a sharp knife. No filing. Once that was snug, I used it as a template. Drawing onto my actual panels, with a high accuracy. Then I chopped out, removing my drawn on line but nothing more. After which they needed the slightest tickle with the file to fit perfectly.



Often having something to draw round makes a huge difference.



If you balls it up, you can get an iec recess panel for peanuts. You can use it to make a washer. Not a washer with a round hole, but one with an iec shaped hole. You just screw it to some wood, so the drill bit in your hole saw has something to center in. It could be a good catch, if it did go wrong
 
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For thick aluminum like that, not sure. For wood or thin metal I draw a template and printed it onto sticky label paper. I stick that to the panel, drill one hole then use a spiral bit on the router to get close to the lines. After that, it's filing. Just be sure to cut within the lines!

Here is what I use. The line on the base helps me to square the cutout to the panel.
 

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Drill a big hole or a bunch of small holes around the cutout as suggested above. Use a round file and square file and it will take less time than you think- even if you have no skill (I don't have any artistic ability at all) it should come out really good.

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Lay the hole out carefully with a scriber and a metal ruler, then drill a hole and use a coping saw to cut out the bulk. If you're careful you can cut very close to the line to minimise filing work. Then use a quality flat file together with a square or triangular file to bring it to the line all the way around.

For proper filing technique see here: YouTube

It will not take all that long and you'll learn a new skill. Important are to use quality saw blades and files, they'll save you no end of frustration, as well as a good way to hold the part during filing such as a vise. Look for a decent used vise and you can get one pretty cheap.

To save some time you can drill around the perimeter of the hole and knock through the remaining material with the coping saw like this:
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If you take your time with a decent file after pre-drilling the profile, you should be fine. Especially if it’s aluminum that you’re cutting.

That’s your best bet, you can replace patience with money, but if there isn’t any money...
Mark the opening well, stop and re-mark it if it gets wiped out during the struggle.
Take a break and come back to it after getting it close, that will help prevent you from over doing it.
 
For what it's worth, here is a technique I use whenever possible (maybe 50% of the times, for straight shapes only):

-Mark the contour using a fine marker, a scriber or equivalent

-Align one of the lines with the top side of a good vise and cut it using a wood chisel for aluminum or a chisel for harder materials if else.
The inner part to be removed has to be on top, the remainder has to be clamped in the vise's jaws (use a buffer material if you fear the jaws might cause damages to the part).


-Continue in the same way for all other sides until the inner part is completely detached

Note that different chisel sizes can be used depending on the lengths to be cut.

Obviously, this method can only be used if clearances are sufficient to allow the clamping into a vise, which is unfortunately not always the case but when it is, the result is excellent, like industrial punching, but I recommend you practice on a blank before committing to the real job, because one needs to acquire a bit of specialized dexterity (not difficult) before risking to ruin a really valuable part
 
Well, if you really have no confidence in the tools you already have like drills and files, might be time to punt. You can source IEC jacks that mount in a round hole, or less costly would be a PowerCon jack. Absolute cheapest would be a Chinese PowerCon, not sure if they're knockoffs or licensed.
 
Someone had mentioned IEC outlets that fit in round holes?

Can someone suggest some manufacturers / part numbers?

It’s not that I can’t make it work, I’d just like it to look clean and there’s a small margin for error.

I might try a few times on a piece of scrap as well just to see how well I do.
 
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