I agree, running thread shall not be used at couplings. Would running thread still need to comply with 345-8 and 346-8(99 code book)? I believe the intent is that all field cut conduit(including running thread)have 3/4" taper on both sides. This would be very difficult to do in the field(improbable if not impossible). That is why they make tools like "nipple chucks" for power threaders. Of course I could be interrupting the code wrong(it would not be my first time).
NEC 346-9(b) Running Threads
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mdshunk
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Here's some PVC running thread that I've used for services a few times. (back to back panel and meter).
http://eel-co.com/products/uni-nipple-standard/standard-Information.html
It has been investigated by the ETL.
http://eel-co.com/products/uni-nipple-standard/standard-Information.html
It has been investigated by the ETL.
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e57
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I used some today in place of a chase nipple, because I wanted a grounding lock-nut for a better ground path. I keep some on the truck for any time I need a nipple of a specific length. A lock nut on both sides of the box is enough for a good connection. IMO the only time it is not allowed is at conduit couplings. Not all products are in the code, and the one and only refferance to it in the code is the one disallowing it for that purpose. That does not disallow it's use anywhere else. 
It's great for going surface to surface through a wall.
It's great for going surface to surface through a wall.jmd445
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The running threads, are the made NPT or NPS (national pipe taper or straight), Jim
mdshunk
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Well, if you run your NPT die on far enough to make a running thread nipple, you'll end up with NPS threads whether you wanted them or not. The manufactured running thread nipples seem to have NPS threads.jmd445 said:
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