To cut a steel beam with an angle grinder, you need to work at a slow methodical pace to ensure that the cut is square. The key to cutting through the steel beam is the thickness of the cutting wheel that you use to perform the cut. A thin cutting wheel will cut quickly, but wears down nearly as fast as it cuts and this results in you using many cutting wheels to finish the cut. The opposite is true for thicker cutting wheels, so you will need to use a cutting wheel that cuts fast and lasts long.
Place the steel beam on top of a stable worktable, resting on a web of the steel beam. If the steel beam is longer than the worktable, support the end of the steel beam with a pipe stand.
Measure and mark the distance that you need to cut the steel beam with the tape measure and soapstone
Extend the mark by aligning the blade of the combination square with the soapstone mark and dragging the soapstone along the blade of the combination square.
Put on your safety glasses, face shield and leather work gloves.
Attach a 1/16-inch thick cutting wheel to the six-inch angle grinder.
Lower your face shield, press the trigger of the grinder and lower the spinning cutting wheel to the soapstone line you made on the web of the steel beam.
Run the spinning cutting wheel along the soapstone line to create a score line across the web of the steel beam.
Continue to run the cutting wheel across the score line until you cut through the web of the steel beam, exchanging cutting wheels as needed.
Secure a new cutting wheel to the six-inch angle grinder, place the cutting wheel in the centre of the cut web and make a deep cut into the centre web of the steel beam.
Flip the steel beam over so the cut web of the beam is resting on the worktable and repeat the process to cut through the other web of the steel beam.
Lay the steel beam on its side and draw a line between the two cuts that extends onto the steel beam's centre web.
Cut the centre web of the steel beam using the same methods you employed when cutting the top and bottom webs of the steel beam.
Secure the six-inch diameter flapper wheel to the angle-grinder.
Run the flapper wheel along the cut edge to remove the burr left from the cutting process.
Before cutting a steel beam with an angle grinder, ensure that the cutting wheels you are using are meant for high speed cutting.