In this instructable, you will learn how to weld and plasma cut. The project itself is a mathematically made fire pit that uses the concept of angles and area to create the perfect square shape. The basic of the project is metal origami with a little adhesive help from welding. It is also is a great threshold to the world of metal.
1.) 36 in. x 36 in. Plain Aluminum Sheet in Silver
2.) 1-1/2 in. x 72 in. Plain Steel Angle with 1/8 in. Thick
1.) Evolution 15-Amp 14-in Chop Saw
2.) Millermatic 250 MIG welder
3.) Lincoln Electric 240-Volt 100-PSI Plasma Cutter with Air Compressor
4.) Kobalt 25-ft Auto Lock Tape Measure
5.) DEWALT 4.5-in 20-Volt Max Cordless Angle Grinder
6.) Metal chalk
7.) Yard Stick
8.) Strong Welding Magnet Arrow Holders (8-Pack)
Step 1: Making the Main Lines (MATH)
First, make sure your Aluminum Sheet in Silveris even on all sides. To start, you want to divide 36 by three. 36/3=12. At every 12" you want to draw a line with Metal chalk . Thus, leaving you with 9 squares on your Sheet. The square in the middle will be the bottom of your fire pit.
Step 2: The Corner Cuts
Each square should be 12x12. The four corner squares are what will be cut with the plasma cutter, later... In the first corner square, measure 6" and mark it with metal chalk. Do the same step on the other edge. Using a Yard Stick, place one edge on the corner of the Base (middle square) and the other end on you 6" mark. Using the metal chalk again, draw a line connecting the two ends. Do the same thing with your other 6" mark. They should both end up meeting on the same corner of the Base. Do this to every corner square.
Step 3: Setting Up Plasma Cutter
Plasma cutting can be pretty simple when you know what you are doing. Since the material that is being used is a thinner material, the voltage on the plasma cutter will be lower. The sheet metal is 20 gauge (.36) width. So the voltage used will have to be very low, or the cut movement will have to be very quick. Personally, I set the voltage to 14 amps (amperages) and did a quick cut. Once you have the settings to the way that best fits your preference attach the clamp to your project. Turn your gas on and flip the power switch (make sure the nozzle is not touching the clipped workspace)
Operating plasma cutter safety guide.
Step 4: Technique
There are a handful of different ways to use a plasma cutter: free handed, using a drag shield, using a line guide, etc...
I started off by using just a drag shield and free handing it. Sadly, my lines turned out to be choppy and uneven (It creates, later on, more work grinding the edges even and also makes it harder to weld). So to fix this problem I ended up using a line guide. I simply just made one by finding a scrap of Plain steel angle I had laying around from another project.
When you first begin to plasma cut you want to make sure the nozzle does not touch the work material. Best way to do that uses a drag shield. It allows you to press against the material without the nozzle touching.
As for the line guide, get the piece of straight scrapped metal. Put it close to your Metal Chalk line (not on or else the cut will not be on the line.) Use the line guide like you would a ruler. The plasma cutter's torch handle is the pencil.
Step 5: All Done Cutting... Now What?
Now that the body of the fire pit is cut, it is now time to "fold" our metal to the fire pit shape.
There are two ways you can bend your metal.
1.) Use a grinder to thin the base creases and then bend by hand.
2.) Cut long pieces of spare metal, then clamp them to your project (makes a cleaner crease)
I did the first one but I will provide a youtube video on how to do the second one.
Step 6: Bending!
To start off, you want to mark where your base is with a ruler and metal chalk (the middle square). These lines are going to be where you grind.
Gently, making a straight line, use the Cordless Angle Grinder to grind on the line. Thus, making that area thinner and easier to manipulate. Now, bend the metal on the line till it is slanted. Do this to all sides of the fire pit. Once finished, they should all look even.
Step 7: Welding!
To start off you will need the Welding Magnet Arrow Holders to hold the sides of your project together well you weld. Locate four magnets inside of the firepit just to hold it well you put a simple dotted weld to hold the sides together well you do the real weld.
The magnets, if placed there for a long time well welding, will start to melt. That's why you dot weld by strategically placing 3-4 circular welds to hold the sides together like "glue" until you can put a whole bead down.
Once you have your dot welds done, you can take the magnets off (if done correctly the dots should hold the pieces together long enough.)
Now you can finish welding the rest of your projects!
Step 8: COMPLETE!!!!
CONGRATULATIONS!!!!!! You are now the owner of a gorgeous, homemade fire pit!!!!