Apprentice answer

What's the trick to seating a stubborn Pittsburgh seam on a large rectangular fitting

1st YearHand Tools, Fasteners & HardwareCheck first

Start at one end. Use your hand seamers or a raw hide mallet to gently start the flange into the pocket. * Work your way down the line incrementally, tapping the male edge fully home into the pocket *before* you start flattening down the locking lip. If you hammer the lip flat prematurely at the start, the rest of the run will bind out of alignment.

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Plain-English answer

Field checklist

Start at one end. Use your hand seamers or a raw hide mallet to gently start the flange into the pocket. * Work your way down the line incrementally, tapping the male edge fully home...

Ask Foreman

Hey boss, I’m checking duct assembly: What's the trick to seating a stubborn Pittsburgh seam on a large rectangular fitting? I found the likely issue and want to verify the next step before I lock it in. Do you want me to adjust it now or check the drawing/detail first?

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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