David Einhorn Posted March 9, 2009 Share Posted March 9, 2009 (edited) Does anyone know a way to **hand** cut tapered wood-screw type threads on the end of a ~1/4" rod, without using a mechanical thread-cutting machine? The rod would be about 10 or more inches long for demonstrating making a mid-1800s canon vent tool. Period correct method very much preferred. The threaded end of the rod *must* be tapered. Is there such a thing as a die for cutting tapered threads? If so where may I find one? Edited March 9, 2009 by UnicornForge Quote Link to comment Share on other sites More sharing options...
dablacksmith Posted March 9, 2009 Share Posted March 9, 2009 ok first question ... why does it need threads? if it is the vent pick they were not threaded.. second thing threads were hand filed during that time...it will take practice but you will be suprised at how nice the threads can come out with a good file! ide start with a triangle file thats real sharp..now when you say mid 1800 are we talking civil war or earlier? civil war era probably done on a lathe ...prior era lathes and industry were still building and not as common as hand labor... good luck! Quote Link to comment Share on other sites More sharing options...
HWooldridge Posted March 9, 2009 Share Posted March 9, 2009 They were also forged in a set of dies. The taper was forged first then placed in a swage that was struck only once as multiple hits will foul the threads. One hit would generate some flash at the parting line and the part would require some cleanup but it still saves a bunch of time with a file. With a little practice, you can also lay down a decent thread by hand on a lathe. Once the initial scratch is made, the remaining cuts follow along. The first threads were made this way - before threading gears and lead screws were invented. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 9, 2009 Share Posted March 9, 2009 While hand filing was common: "Mechanic Exercises" published in 1703 mentions using a die plate to cut threads. So not all threads 100+ years earlier were hand filed---though it also mentions filing larger ones out wrt making a clock work jack. The 19th century gimlets I have seem to show evidence of hand filing as well. Tapered threads were evidently not the norm back then as I have seen the non-tapered period wood screws before too. Quote Link to comment Share on other sites More sharing options...
David Einhorn Posted March 10, 2009 Author Share Posted March 10, 2009 Actually it would be a canon gimlet to remove the primers from canon's vent, and not a vent pick, my bad. Period government specified CW gimlet, for use with field equipment, has tapered thread, with a flat spot just above the thread that increased the likelihood of the primer to clamp onto the gimlet. It might make a decent demonstration item if it can be made in less than 10 minutes. Anyone know a source for dies for tapered threads? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 10, 2009 Share Posted March 10, 2009 Hot twisting? if you can run the heat in from the larger cross section you can sometimes get very even twists on tapered stock as it will twist tightest where it's hottest *or* smallest in crossection and so you can play with the heat to get it to twist evenly. Quote Link to comment Share on other sites More sharing options...
David Einhorn Posted March 11, 2009 Author Share Posted March 11, 2009 Not sure how one would do that at the end of a pointed rod.Hot twisting? if you can run the heat in from the larger cross section you can sometimes get very even twists on tapered stock as it will twist tightest where it's hottest *or* smallest in crossection and so you can play with the heat to get it to twist evenly. Quote Link to comment Share on other sites More sharing options...
RLD Posted March 11, 2009 Share Posted March 11, 2009 the gemlet in the artillery manual was made by tapering the end of the rod leaving a lug past the taper. heat the taper and freeze the lug end from the shoulder to the end. put the end in the vise and twist the rod until the tip breaks off. this leaves a nice point that will get into the end of the primer. Quote Link to comment Share on other sites More sharing options...
anvillain Posted March 11, 2009 Share Posted March 11, 2009 Not sure how one would do that at the end of a pointed rod. That would not be too difficult Unicorn, You would taper in the middle of the rod. If you have access to a small torch it would be easier to control the heat. Then you would actually be twisting two screws at the same time. Then when you get it to your liking, cut in the middle of the twists with a hacksaw or just file around the bar to weaken it and break it apart. In the absence of a torch for localizing the heat just heat both tapers a little more than needed then pour water where you DON'T want it twisted. I'll bet you won't have much trouble getting some respectable tapered threads. This isn't just theory, I have actually done this. The tapers I made were four sided and were not used as screws. The rest of this is theoretical. I believe if you make your tapered cross section diamond-shaped with two opposing corners rather sharp that you will get something resembling a wood screw thread. Let me know if this works for you. I will also try it myself. Anvillain Quote Link to comment Share on other sites More sharing options...
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