Brodhead Pietenpol Association

Original Posted By: "Jack Phillips (EUS)"
Subject: Pietenpol-List: Re: Rolled vs. Cut ThreadsHey gang,One of the cool things about a list like this is some of thegeneral things that you pick up while gleaning facts about aparticular aircraft. For instance, I realized that there appearsto be another way to thread a spoke or other piece of metal otherthan "cutting" threads. I assume that cut threads are what I amfamiliar with; cut with a die twisted over a round piece ofmaterial. From the discussion it appears that "rolled" threadsare done differently and may have different strengthcharacteristics. Who can fill me in on the differences in methodand strength(s) between the two and where which shoud be used.Thanks,Mike BellColumbia, SC________________________________________________________________________________

Original Posted By:> Mike Bell [SMTP:mbell(at)sctcorp.com]
Hi Mike,Rolled threads are made by rolling the wire between two die plates with aset of parallel grooves cut into the plates. The grooves are set at thecorrect pitch angle to impress the thread form onto the wire. Essentiallythe threads are "cold-forged" into the wire, producing a much strongerthread. Cutting threads usually results in some nicks and scratches at theroot of the thread which produce stress concentrations and provide placesfor cracks to begin. Since the thread rolling process sort of mashes themetal into shape, the surface is left under compressive stress, whcih allowsit to better resist tensile loads.Sorry for the technical jargon. I'm an engineer and tend to think in suchterms. Now for the simple version: Rolled threads are stronger for tworeasons - not only are the threads produced smoother, but no metal isremoved to produce the thread, it is simply moved around to the propershape. They are actually cheaper to produce once the dies are made, sincethe threads can be rolled very quickly (threads for spokes can typically berolled in under a second - you can't cut threads that fast withoutoverheating the wire). Most high strength thread applications such as wheelspokes or flying wires use rolled threads.I have a picture in an old textbook showing the process. I can FAX it toyou if you provide me with a fax number, in case my description above isn'tclear (which it probably isn't). Jack Phillips Raleigh, NC > -----Original Message-----

Original Posted By: Rodger & Betty