Sheet Metal and Fabrication Flashcards

When using aviation snips to cut sheet metal, which color handle is used for straight cuts?

Answer: Yellow

Yellow-handled aviation snips are designed for straight and wide-curve cuts in sheet metal.

What is the correct bend allowance concept used when laying out a sheet metal fitting?

Answer: Extra material must be added to account for metal that stretches during bending

Bend allowance accounts for the arc length of metal at the neutral axis during bending, so extra flat length is included in the pattern.

Which duct sealing class per SMACNA requires sealing all transverse joints, longitudinal seams, and duct wall penetrations?

Answer: Class A

SMACNA Seal Class A requires sealing all transverse joints, longitudinal seams, and duct wall penetrations for the highest level of airtightness.

What type of fitting connects a rectangular duct to a round duct?

Answer: Transition fitting

A transition fitting (also called a square-to-round transition) is used to connect rectangular and round duct sections.

In sheet metal layout, what tool is used to scribe a parallel line at a fixed distance from a straight edge?

Answer: Dividers or a scratch awl with a straightedge

Dividers or a scratch awl guided along a straightedge are used to scribe accurate parallel layout lines on sheet metal.

What is the minimum recommended clearance between a sheet metal duct and combustible construction according to NFPA 90A?

Answer: 0 inches for sheet metal duct (no clearance required)

NFPA 90A allows sheet metal ducts to be installed in contact with combustible construction because sheet metal itself does not ignite.

Which type of duct configuration is most efficient for distributing air to multiple zones from a single air handler?

Answer: Extended plenum trunk-and-branch system

An extended plenum trunk-and-branch system efficiently distributes air by maintaining relatively constant static pressure along the main trunk while branches tap off at multiple points.