FILENAMES: rolled_copper_threads.jpg rolled_clamshell_holder.jpg DESCRIPTION: These are pictures of a rolled copper thread and fixture used to hold it. Posted by Glen . The following description was provided: ================================================================= Thread rolling, perfect threads in a flash "Rolled copper threads" shows the 5/8-11 threaded blank, total threading time approximately 5 seconds. "clamshell holder" shows the method used to hold the threaded end for the second operation. The part is a copper conductor for large amperage DC motor feed, it is being produced in a bar fed CNC lathe. A center is used to turn the thread blank diameter, after it is withdrawn the blank is pushed back toward the collet and reclamped, this was done because there is not sufficient room for the thread rolling head to be used with the tailstock ram that close, consequently the blank turning was done about 9 1/2" from the collet face. The thread length is 3". It is clear that a lathe with a retracting tailstock would excel at this sort of thing, the whole tailstock sliding forward and clamping to the ways by an M code, the ram extending, the blank turned and then the tailstock unclamping and retracting out of the way. Previous to rolling this thread (actually it was a 7/8-9 thread the first time) the single pointing in the CNC lathe was a 2 minute operation that required pressing single block about 10 passes before completion, shutting off the coolant, and applying MolyDee with a brush by hand after turning the single block off and pressing cycle start again. Failure to use that method guaranteed threads with chunks ripped out. That was using a full form (laydown style) insert. Hardly a "walk away and do other things" proposition, and that is what we always try to achieve. The Fette F3 head cost $2400 approximately, and rolls were another $240 per set. The head will do all coarse threads from 7/16-14 to 7/8-9, each thread needing it's own roll set. To do fine threads requires the purchase of a different head and rolls. Thread blank preparation is a bit more delicate than for single pointing, tolerances must be held a little tighter as each .001 diameter change produces approximately a .003 major diameter change. Although the blank diameters and the head can be adjusted to produce a burnished thread from root to crest it is said the rolls will last far longer if the blank diameter is adjusted so that the very tops of the threads are not finished, the difference being hard to see without magnification. After the part was turned, threaded and knurled it was cut off and the process began again, and it was not necessary to attend to the machine until the near the end of the bar. The second operation required drilling, boring and taper threading, unfortunately since it was not a standard taper that thread was single pointed, but being a finer pitch it did not need the application of cutting oil. The total order was 250 parts for each thread size, and expectations are very high that this will be repeated regularly. The folks at Fette made this first time experience easy for me, and it was one of those things that seems, in retrospection, hardly worth the anxiety that crossed my mind at the thought of producing a thread at over 800 RPM in one pass. Also one of the posters in alt.machines.cnc, Brewster, was a great help, spending time writing several emails that answered many questions I had asked. In conclusion I would say that deciding to use the thread rolling process is related to the quantity of parts being made, the strength required in the thread (rolled threads are somewhere around 15% stronger than cut threads) the specifications of the customer and of course the availability of the capital to purchase a head and rolls if they aren't in inventory. Two minutes thread cycle time compared to five seconds might mean selling the kids bicycle to get the money, or perhaps some of the wife's jewelry. (just a joke!) Over a certain quantity of parts it becomes uneconomical to NOT roll the threads. Glen