BIG thread chaser source

Need a tool to chase the rust out of threads on
irrigation riser sockets.
Thread is 4" NPT internal. Yes---that's FOUR
Any ideas? I've never personally seen a pipe
tap that big, and I'm sure the price
would scare me. Might just have to offset the
tailstock and make one. I think I've
got a chunk of 5" 8620 around here somewhere.
Does anybody have a source for a 4" internal
thread chaser?
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Would a wire brush work for you?
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"Ignoramus27719" wrote: Would a wire brush work for you? ^^^^^^^^^^^^^^^^^^ How about making a few hacksaw cuts across the threads of a nipple, so it acts sort of like a tap? If that works, but wears too fast, then case harden it.
Reply to
Leo Lichtman
Interesting, there's a tool for large external threads
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But its over $500.
Their internal tool is just the insert on a handle.
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Inserts are about $15, maybe some creative thought will yield an interesting solution.
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