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Fabrication Techniques Flashcards

6 cards from real 308A practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is an S-cleat and where is it typically used?

    Answer: An S-shaped metal strip used to join the longer sides of rectangular duct sections together

    An S-cleat is a formed strip of sheet metal with an S-shaped profile. It slides over the edges of two adjoining duct sections, connecting them along the longer (non-drive-cleat) sides of rectangular duct.

  2. When fabricating a round duct elbow, what is the 'throat' radius?

    Answer: The radius of the inner (tighter) curve of the elbow

    The throat radius is the inside radius of the elbow — the tighter curve. Combined with the duct diameter, it determines the centerline radius and the overall size and airflow characteristics of the elbow.

  3. What is the recommended overlap for a longitudinal lap seam on round duct?

    Answer: 3/8 to 1/2 inch

    A longitudinal lap seam on round duct typically has a 3/8 to 1/2 inch overlap, which provides enough surface for rivets or screws while minimizing material waste and maintaining a smooth interior.

  4. What is the purpose of a 'standing seam' in sheet metal roofing and architectural work?

    Answer: To create a raised, interlocking seam that sheds water and allows thermal movement

    Standing seams project above the panel surface, creating a water-shedding joint that also accommodates thermal expansion and contraction. They are the premium seam type for metal roofing.

  5. What tool is used to set a Pittsburgh lock seam after the edges have been formed?

    Answer: A hand seamer and mallet or a closing machine

    After the Pittsburgh pocket and lock edges are formed and engaged, a hand seamer is used to close the seam flat, and a mallet is used to set it. Production shops may use a closing machine.

  6. What is the standard method for reinforcing large rectangular duct to prevent flexing?

    Answer: Installing angle iron or channel reinforcement (tie rods and angles) at specified intervals

    Large rectangular ducts require external reinforcement using angle iron, channel, or tie rods at intervals specified by SMACNA standards. This prevents the duct walls from flexing under pressure.

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Sources & references

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  1. skilledtradesontario.ca — Renewal, retake fee, score validity, test delivery, fees, retake policy, passing score, score release, time limit · verified Oct 2026
  2. red-seal.ca — Exam format · verified Oct 2026