So this is a quick question from one of our friends. They ask how do you make a square hole in something without special tools?
This is pretty common and depending on the material you are working with the tools you will use will be slightly different but it is possible to make pretty good square holes in things with common tools you probably have in your shop.
The first thing you need to do is layout the hole placement on whatever you are putting it in. If you are cutting the hole in wood then you can scribe the hole on both sides of the piece and then use a chisel that is slightly smaller to mark the location about an 1/8th of an inch deep. The chisel mark will keep you honest and on target.
The next thing you need to do is scribe an X in the square and find the center. Once you find the center use a center punch to mark where your drill bit will be located. You want to use a drill bit that is as close to the size of the hole as you can and then drill through the piece. Hopefully you hit your mark on the other side when the bit exits. This is best performed on a drill press but if you don’t have one you will have to use a hand drill. A tip for hand drilling is you may want to use a 1/8ths inch drill bit to make a hole first and drill in from each side of the piece and hopefully the centers meet. The pilot hole will guide your larger bit when you are making the final pass.
Now that you have your hole drilled you need to make the opening square. If you have a three sided file you can use that or you can use your chisel if the hole is larger. Make sure that you look at both the opening and exit sides as you work and it is best to start the ends on both sided and get them square before you work on the center.
Square Holes in Metal
If you are working on metal the task will be a little harder but it is just about the same. I would suggest that instead of using a chisel that you mark the square opening with a scribe.
If you are working on a thick piece with a wide square opening then the best bet is to center punch the center of the hole like you did above and use a small bit to drill through. The next step is to use the same small bit and drill the corners just inside your scribe line. This will make it easier later when you are cleaning up the corners.
Now drill out the center of the hole and then use a file or a die grinder with a small tip to sharpen up the corners of the square. You can then work on the material inside the hole with a file to make the entire opening square.
Final Note
Making square holes is something you will come across and there are special punches to do this in manufacturing. They would also drill out the center of the hole but then come back with a square punch that would accurately cut through the meat left in the corners.
Since most people or even shops don’t have access to industrial presses with dedicated cutting tools you have to do the best you can.
A lot of different tools can help you including a jig saw or a hack saw that you can place in the round opening to cut out the meat in the corners. Do your best and remember to take your time. Its not like you are doing this every day.