How to make square holes with round drills, a method available to everyone

In the manufacture of various mechanisms, it may be necessary to drill a square hole. For this, there is a Watts drill, but not everyone has it. If buying it is impractical, then using simple technology, you can make a square hole with ordinary metal drills.

Instruments:

• punch;
• hammer;
• drill or drilling machine;
• center drill;
• a core drill of 4 mm or more, depending on the size of the required square hole;
• a large drill with a diameter of 1 mm less than the side of the future square;
• file for metal.

Square hole drilling

For convenience, you need to cut out a square template from paper, but less than the required hole by the diameter of the main drill. For example, if you need a 10x10 mm square, while a 4 mm drill will be used as the main one, then the template is cut out with sides of 6x6 mm.
Important! When choosing the main drill, it is necessary that its 2 diameters be slightly smaller than the side of the template. In this case, the holes during drilling will not overlap and the drill will not come off the desired point.
The paper square is glued to the workpiece with tape. With the help of a center punch, distinct deep notches are applied at its corners and center. After the template is removed.
The notches are slightly drilled with a center drill.
Further, through the corner marks, you need to make through holes. Ideally, use a drilling machine, because when working with a drill, it is possible to reduce accuracy. If you need to drill thick metal, you will definitely need oil to cool the edge of the drill.
After the corners are ready, with the help of a large drill, a central notch is drilled between them. This allows you to select the metal in the middle. The result is a blurry square hole.
Using a file, flat or triangular file, bring the hole to the correct square. Particular attention should be paid to rounding at the corners to grind them at 90 degrees. It is desirable that the width of the file corresponds to the side of the square hole, then it will turn out to hold the bore almost perfectly.
This method of drilling is time-consuming and takes at least half an hour, given the finishing file, but allows you to get a sufficiently high-quality hole. Its main advantage is the ability to dispense with a meager set of tools without the need to buy a Watts drill.