Welding is the process of using extreme heat—and, sometimes, pressure—to attach two pieces of metal. In contrast, metal fabrication is a more involved process that can include welding, sheet metal work, bending, and other forms of metal manipulation. Metal fabrication is a large-scale project that may or may not involve welding, while welding is more often a step in larger fabrication projects.

Cutting rectangular ductwork requires careful measurements and the right technique. Use a measuring tape and pencil to mark the cutting lines accurately. Tin snips are excellent for straight cuts on smaller ducts. For more extensive or thicker rectangular ducts, a reciprocating saw with a metal-cutting blade is effective. 

Ensure the duct is well-supported and secure while cutting to prevent wobbling and maintain precision. After cutting, use a metal file to smooth any sharp edges, ensuring safety during installation. 

Welders use a variety of methods in their trade. Different types of welding are better suited for different purposes and contexts. For example, stick welding is a versatile form suitable for most metals and alloys. The most common types of welding include:

• Stick welding: $100–$1,000

• Metal Inert Gas (MIG) welding: $250 and up

• Tungsten Inert Gas (TIG) welding: $250 and up

• Gas welding: $150 and up

• Forge welding: $15–$25 per hour

Cutting round ductwork requires precision and the right tools. A duct cutter, specifically designed for circular ducts, is ideal. First, mark the cutting line on the duct using a measuring tape and pencil. Then, position the duct cutter's blade on the marked line. Apply steady pressure, rotating the cutter around the duct. The sharp blade creates a clean, precise cut. Alternatively, a reciprocating saw with a metal-cutting blade can be used for larger round ducts. Ensure the duct is securely held in place while making the cut to prevent slips and maintain accuracy.