How to Weld Square Tubing

Welding square tubing is fundamentally the same welding process as any other type of material. On a standard 45 degree corner, you will have one fillet weld, one corner weld and two flat welds. The corner and fillet welds require no prep work other than removing rust, dirt or debris from the weld area. The two flat welds will need to be cleaned and beveled. The bevel will ensure that you have proper penetration on both pieces of square tubing being jointed.

Difficulty: Moderate

Instructions

Things You'll Need:

• Square tubing
• Combination square
• Scribe
• Band Saw
• 4 inch grinder
• 4 inch hard grinding wheel
• MIG welder
• Leather welding gloves
• Welding hood
• Framing square

1. Cut two pieces of square tubing such that each has one 45 degree angled end. Set the band saw on a 45 degree miter cut. Clamp the square tubing into the band saw vise. Remove the mitered piece of tubing. Repeat the procedure on the other piece of square tubing.

2. Attach the 4 inch hard grinding wheel to the grinder. Remove the burr from all four sides of each piece of square tubing. Bevel each side of the square tubing that has the 45 degree cut, half of the thickness of the wall of the metal tubing.

3. Place the two pieces of square tubing flat on a table, with the miter cuts facing each other. Bring the mitered sides of the tubing together. Leave a 1/16 inch gap between the two pieces of tubing. Place the framing square at the corner created by the two pieces of square tubing to set the corner at 90 degrees.

4. Turn on the welding machine. Put on the leather welding gloves and the welding hood. Place a tack weld on the inside point of the mitered corner at the fillet weld. Check the corner against the framing square to ensure that the corner is still 90 degrees. Place a corner tack on the back side of the mitered corner. Re-check the corner for square. Place another tack on the flat surface of the square tubing that has the 45 degree cut running across its face. Flip the two pieces of square tubing over and tack the face that was lying flat on the table.

5. Weld the rear corner weld of the square tubing first. Place the MIG gun at the top of the corner, with the tacked pieces lying flat on the table. Lower your welding hood. Depress the trigger and drag the puddle downhill to perform the weld. Spin the two pieces of square tubing and perform the fillet weld on the inside of the corner. Start the weld at the top and drag the weld downhill while moving the MIG gun in a circular pattern to stitch the weld evenly to both pieces of square tubing.

6. Weld the 45 degree miter cut flat. Start the weld at the inside corner and work the weld to the outside corner of the mitered joint. Flip the tubing over and weld the last flat 45 degree cut side. Perform the weld in the same way as the opposite side, from the inside corner to the outside corner.

7. Grind the corners after the welds have cooled to have a seamless 90 degree bend in the square tubing.