This all depends on the tools you have on hand and whether you’re trying to cut a straight line or shapes. 

The best tool to use for straight lines is either a circular saw or table saw. When cutting shapes, a jigsaw will be the easiest and most precise tool to use. 

There are a few things you can ask welders before you hire them to get an idea of their experience and ability levels:

• Are you licensed and certified?

• How long have you been in the welding business?

• Do you commonly do the type of welding I need?

• Do you offer any kind of warranty for your work?

• Do you charge by the hour or by the project?

• How long do you expect my welding project to take?

• What steps do you take to minimize errors in your work?

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.

Your typical household tools will not cut a metal pipe. To cut a metal pipe, you’d need more specialized tools like a pipe cutter or circular saw. Do not attempt to use these tools without taking proper safety precautions and wearing safety gear. It’s usually safer to let a pro cut a metal pipe, especially if you’re not confident in your skills with a heavy-duty saw.