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Apprentice Q&A · #194

We are short on 24x24 duct, but we have a plasma cutter and flat stock. How do I fabricate it entirely in the field?

4th YearAdvanced Problem SolvingRED · Stop / Verify

Calculate your complete metal blank layout wrappers allowance factoring in the standard 1/2-inch allowances for the Pittsburgh corner seams and S&D connection tracks. * Program or manually trace your cut lines out onto your flat galvanized stock sheet panels. Cut the profiles cleanly using your tools, run the long edges through your field pocket-lock machine or hand seamers to knock the matching Pittsburgh wrappers together, and true up the box profile using a framing square before driving the s

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Plain-English answer

Calculate your complete metal blank layout wrappers allowance factoring in the standard 1/2-inch allowances for the Pittsburgh corner seams and S&D connection tracks. * Program or manually trace your cut lines out onto your flat galvanized stock sheet panels. Cut the profiles cleanly using your tools, run the long edges through your field pocket-lock machine or hand seamers to knock the matching Pittsburgh wrappers together, and true up the box profile using a framing square before driving the seams home.

Field checklist

Ask Foreman

Hey boss, I’m on advanced problem solving and need verification before I touch this: We are short on 24x24 duct, but we have a plasma cutter and flat stock. How do I fabricate it entirely in the field? Do you want me to stop here and check the approved detail, submittal, or inspector/manufacturer requirement first?

Open Ask Foreman

Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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Related mistakes & recovery checks

#025 · Forgetting to add allowance for the slip and drive connection when cutting duct1st Year · Sheet Metal Work#107 · Using a plasma table program that hasn't been proofed, wasting a full sheet3rd Year · Tools & Equipment#005 · Not using gloves when handling freshly cut sheet metal edges1st Year · Safety