308A Fabrication Techniques

Question 1

What is the primary purpose of a Pittsburgh lock seam in sheet metal ductwork?

Accepted Answer

To create a strong, airtight mechanical joint without welding

Answer

To provide a decorative edge

Answer

To reduce material usage

Answer

To increase airflow velocity

Question 2

What is the maximum gauge of galvanized steel that can typically be formed on a standard hand brake?

Accepted Answer

22 gauge

Answer

28 gauge

Answer

16 gauge

Answer

10 gauge

Question 3

When using a slip roll former, what determines the minimum diameter of a cylinder that can be formed?

Accepted Answer

The diameter of the upper (adjustable) roll

Answer

The length of the rolls

Answer

The speed of the machine

Answer

The colour of the metal

Question 4

What is the purpose of 'beading' on a round duct fitting?

Accepted Answer

To add rigidity and strength to the fitting and provide a point for connection

Answer

Decorative appearance only

Answer

To reduce the weight of the fitting

Answer

To mark the fitting for identification

Question 5

What is the correct procedure for notching a corner on a sheet metal pattern before forming?

Accepted Answer

Remove a precise amount of material based on the seam type and material thickness to allow clean folding

Answer

Cut a random shape at the corner

Answer

Do not notch; fold the extra material over

Answer

Drill a hole at each corner

Question 6

What type of shear is best suited for cutting internal openings in sheet metal?

Accepted Answer

Throatless shear or aviation snips

Answer

Squaring shear

Answer

Ring and circle shear

Answer

Power guillotine shear