Fabrication Techniques Flashcards

What is the recommended method for cutting galvanized steel to minimize exposure to zinc fumes?

Answer: Use mechanical cutting methods such as shears, snips, or plasma with proper ventilation

Mechanical cutting methods do not produce zinc fumes. When thermal cutting is necessary, proper ventilation and respiratory protection are required to protect against zinc oxide fumes which cause metal fume fever.

What is the function of a 'turning machine' (or elbow edging machine) in sheet metal fabrication?

Answer: To turn or flange the edges of round fittings like elbows and tees for assembly

A turning machine creates flanged edges on round fittings such as elbows and tee sections. This turned edge allows the pieces to overlap and be fastened together during assembly.

When using a rotary machine for crimping round duct, how deep should the crimp typically be?

Answer: Approximately 1/4 inch deep, enough to reduce the diameter for insertion into the next piece

Crimping reduces the diameter of one end by approximately 1/4 inch, creating a slight taper that allows the crimped end to slide inside the adjacent duct section for a friction fit connection.

What is the advantage of using self-drilling screws (Tek screws) for sheet metal assembly?

Answer: They drill their own pilot hole and tap threads in one operation, speeding assembly

Self-drilling (Tek) screws have a drill-point tip that pierces and drills through the sheet metal, then the threads tap into the hole — all in one operation. This eliminates the need for pre-drilling.

What is a 'cleat' in sheet metal duct fabrication?

Answer: A narrow strip of metal used to connect two duct sections together at their transverse joints

Cleats are narrow strips of sheet metal formed into specific profiles (drive cleats, S-cleats) used to mechanically join the ends of rectangular duct sections together at transverse joints.

What is the purpose of 'cross-breaking' a sheet metal panel?

Answer: To add rigidity by creating a slight diagonal crease across the panel surface

Cross-breaking puts a slight bow or crease diagonally across a flat panel, which dramatically increases its rigidity and resistance to vibration and oil-canning (flexing or popping).