You will be surprised at how easy it is to cut a circle in sheet metal. In this tutorial, we are going to walk you through three potential ways you can tackle the problem. All of them are viable options, although do bear in mind that some may be a little tougher than others. It all depends on the metal you are working with and the quality of the tools you have.
If you want to cut a circle in sheet metal, there are 3 main ways. You can use a hole saw (which requires a drill), cut the hole out with some tin snips (best for softer metals), or use a technique known as chain drilling, which is best for larger holes.
There are some methods you can use that we have not covered here. However, we find that the methods discussed here are probably the easiest ways to cut a circle in sheet metal. For example, you can use a hacksaw or piercing saw, but it would take forever.
Method #1: Use a Hole Saw to Drill
Our first method is to use a hole saw. For this, you will need the following:
- A drill. Could be a drill press, although any drill will be fine. Sheet metal isn’t tough to get through
- A hole saw (Our pick – XDOVET Bi-Metal Hole Saw Kit)
- A small HSS drill bit as the pilot.
A hole saw is dead simple, because you are literally drilling a circle into that sheet metal. However, this isn’t the best method for larger holes. Large hole saws can get incredibly expensive.
This method is going to be the best choice for those that want to cut smaller circles in a piece of sheet metal i.e. those ones a bit bigger than your typical drill bit.
Step 1
The first step is to drill yourself a pilot hole. Most hole saws will have a pilot drill bit built into them (this will be in the arbor that you attach to the drill). However, we recommend that you make your own pilot holes. This will It make it a lot easier to guide.
Step 2
Place the hole saw into your drill. If you have purchased a quality hole saw, then you will first need to screw the arbor into the hole saw. It is this arbor that will then be placed into the drill, much in the same way that you would use a standard drill bit.
Step 3
Now all you need to do is drill that hole! The pilot drill bit in the center of the hole saw will need to be placed dead in the center of the hole you want to drill. You want to go slowly with this. While it is unlikely that the pilot drill will slip, you don’t want to run the risk.
The hole saw should be doing most of the work. As the pilot drill on the arbor drills into the sheet metal, it will guide the hole saw through. A good cut should be incredibly quick, and if you have a decent hole saw, you probably won’t need to sand down anything. You just have a perfect circle in your metal.
Method #2: Cut a Circle Using Tin Snips
The second method is ideal for thinner and softer pieces of metal. It may end up creating a somewhat uneven circle, though. This means that you will need to tidy things up a little bit afterward.
Necessary materials:
- Tin snips (Our pick – Hurricane 10 inch Aviation Tin Snips)
- Metal punch and hammer (or you can drill a hole)
- Die grinder, or glass paper
- Metal compass (Our pick – Mr. Pen Professional Compass)
A note on tin snips
For this job, you are going to need tin snips, also known as ‘aviation snips’. These can get through much tougher metals than traditional tin snips. In fact, there is very little sheet metal that they won’t be able to cut through. Due to the way in which their handles have been designed, the cutting should be incredibly effortless.
You will notice that there are both straight and curved tin snips on the market. Straight tin snips, as the name suggests, will be ideal for cutting straight lines. Curved tin snips are for cutting tight curves. Since you are cutting a circle, you would ideally be using both. However, you can use just straight tin snips, you just have to be more careful.
Step 1: Marking Your Circle
You now need to mark your circle. A metal compass is going to be your best bet for this. The metal compass needs to be pointed at both ends. This way you will be able to score the metal in a circle.
Step 2: Drilling Your Opening Hole
There are two routes you can go down here. The first is to use a metal punch and whack it incredibly hard with a hammer/mallet to get through the sheet metal. The second is to drill a hole. This is the better method, in our opinion. This is because it will allow you to create a much larger opening hole.
It doesn’t really matter where you place the hole, although the closer it is to the center of the circle, the better.
Step 3: Cutting The Circle
You now need to force your tin ships into that opening hole and cut away. If you are using aviation snips, then it should be fairly effortless. Just make sure you are following the outline of the circle that you created with your compass earlier.
If you have your curved aviation snips, then cut close to the edge with the straight tin snips, and then use the curved tin snips to cut along the outline of the circle. Your job will be incredibly easy like this.
Step 4: Cleaning Up The Hole
The final step is to clean up the hole. A die grinder will be a good option here. Many people will actually use a Dremel or similar multi-tool. If you do not have a power tool that can do this, then some glass paper will work in a pinch. It will take a little bit longer, though.
Do bear in mind that if you are using straight tin snips to cut the entirety of the circle, the edges will be much more ragged than if you used the curved snips.
Method #3: Chain Drilling
Our final method is chain drilling. This method can be used for any size circle. However, it is going to be quite time-consuming as there will be a little bit of clean-up at the end.
Necessary materials:
- Metal compass
- Selection of HSS or cobalt drill bits
- A drill. Any one should be fine. All are capable of getting through metal.
- Die grinder (Our pick – Dewalt 20V Max Die Grinder)
Step 1: Drawing a Large Circle
The first step is to draw the circle on your piece of sheet metal. You will need to use your metal compass with a metal scribe for this. This circle is going to be the hole that you will be cutting out.
Step 2: Drawing a Smaller Circle
Leaving the center of the compass in place, move the outer arm of the compass inwards slightly, by around 1/4″ to 1/2″. Scribe this smaller circle onto the sheet metal.
Step 3: Cutting The Circle
You should now have two circles. Go through your set of drill bits and look for a drill bit that fits perfectly between the two circles (i.e. the two lines). If you don’t have something that fits perfectly, try and get as close as you possibly can. You now need to go around the outside of the inner circle and drill holes in between the two lines.
You will want to ensure that these holes are touching. This is going to be a time-consuming process, but once you get to the end, the center of your hole will just fall out.
Step 4: Cleaning It Up
The final step is to smooth the edges. There will be some roughness in your circle. However, a die grinder or a piece of glass paper (probably a medium to rough grit) will be able to clean the bulk of this up for you. Don’t go too rough with the die grinder, though. You don’t want to be taking chunks out of the metal!
Conclusion
That’s really all that you need to do to cut a circle in sheet metal. As you can see, you don’t need any expensive tools. All you really need is a drill. You don’t need anything too crazy, such as a bandsaw.
If you need to cut a lot of circles, then we suggest that you use the hole saw method. If you need to cut just one or two, then either of the other methods will work for you.
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