Cutting a hole in galvanized sheet metal

Cutting a circle hole in galvanized sheet metal

When I set up the jigsaw tool as a table jigsaw I didn’t set it up with the idea of cutting metal in mind, but once I realized how good and easy it was cutting wood strips with it, the question of how well it would cut metal was a must. Cutting aluminum should not be a problem, after all a couple of mm thick aluminum sheet can even be cut with a hand scroll saw like the one used in school for handicrafts. But cutting a hole in the shape of a circle in a galvanized steel sheet seems to be more difficult.

It turns out that a few days ago a friend asked me how to cut a circular hole in a galvanized metal sheet a little more than 1mm thick, so it was the perfect occasion to put the machine to the test. I needed to cut a couple of 17cm in diameter holes, and since that is a fairly wide circle I figured they wouldn’t give me too much trouble, so I offered to cut them.

How to cut metal sheet with jigsaw

How to cut holes or circles in metal

Drilling the metallic sheet to pass the cutting blade through

With the help of my compass first I draw the circles on the galvanized sheet of metal. With the drill and a metal drill bit I drilled a hole in both sheets somewhat separated from the circumference line, but the diameter of the drill bit was not enough and I had to drill another hole next to it and join them by forcing the drill bit from one of the holes to the other.

Approach cut to cut the metal circle

To make the cut I use a Bosh jigsaw blade for metal. I know that sometimes I use some cheap tools, but when it comes to buying cutting blades it is really worth spending a little more money on a quality one, as it is very noticeable in the ease of making the cut and how the cuts are more clean.

I install the blade in the jigsaw blade clamp, I place the galvanized metallic sheet on the table passing the blade through the hole I just drilled, and I start cutting the circle hole. Notice that I took away the guide with bearings for perfect vertical cuts. And it cuts without too much trouble.

I start cutting the metal almost parallel to the circumference line, making an approximation cut to get progressively closer to the circumference line as I cut. Once on the line, the only difficulty in following the line is the weight of the metal sheet, which makes the fingers of the hands get tired sooner as expected. It is advisable to stop when necessary to prevent fatigue. Otherwise we won’t be able to follow the cutting line of the circle with acceptable accuracy.

You can’t see it well in the picture I took, but it is curious to see how all those little metal shavings are stuck to the cut I made in the metallic sheet. I suppose that somehow, when cutting metal it can be magnetized. And with all those metal shavings removed, we see how a very clean cut is left on the metal and it is only necessary to pass a file to leave the edge perfect, nothing to do with the cuts left by an electric grinder.

Bosh cutting blade for jig saws

When I remove the cutting blade I notice that it has an area that looks burned, and it is that by not using the guide that keeps the blade vertical the jigsaw blade bends sideways as I push the metal sheet to follow the line of the circle. This causes the blade to rub continuously against the wood of the table top, getting very hot and resulting in that burning.

However, at no time did I have the impression that it lost its cutting capacity. What worries me the most is that the excessive heat may cause some wood chips to ignite, so when cutting metal with this blade it is advisable to stop, not only to rest, but also to allow the blade to cool down.

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