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Long skinny threading

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  • Long skinny threading

    I find this web site fascinating because there is so much to learn. I have a newbie question and if this has already been addressed somewhere on this site please steer me to it. The searches I could dream up were not fruitful.

    Being a woodworker with decent metal working capability, I collected some wood that I wish to make into 12" capacity hand screws; a bakers dozen of them. I have the jaws made and the short dowels that have cross threads, left and right hand. Now the challenge is to cut the threaded rods that pull the jaws together. Each 3/8"-16 x 18" long rod has 9" of left hand and 7 1/2" of right hand thread. Two are used for each hand screw and threaded through the dowel pins to pull the jaws together and apart. It has taken me nearly a week to use a hand die to cut all the threads on a pair of rods. Granted, I'm old, weak and can't pay attention to work steadily at it.

    One method I tried was to clamp the die in my 3 jaw lathe chuck and secure the rod on center using the tool post and by running the lathe as slowly as I could under power (not slow enough) feed the rod by feel through the turning die. Thought about using the thread gear but didn't. About half way through the 3/8" rod twisted off in spite of good lube and adequate feed. Just too much torque.

    At this point I'm out of ideas. Do not have a steady rest, so would have to make one if I try to cut this skinny rod with a single point cutter. Any suggestions? Thank you in advance. Meanwhile, back to reading all of the "Shop Made Tools"....

    Edit: the steady rest could be as simple as a block with a 3/8" hole in it traveling right next to the cutter. Might give that a go....

  • #2
    This is a bit of a hack, but you could buy a length each of 3/8" all thread in left and right hand, turn the ends of one piece down to say 1/4" and drill/ ream the other out to a hair over that. The glue or pin the two together. Would take a lot less time than cutting the threads yourself


    • #3
      The Woodwright's shop TV show had a least one episode showing how to make an adjustable die for wood threads. You are making Acme or square threads aren't you?


      • #4
        I don't think he's threading wood. He's threading metal to make wood hand screw clamps.

        I think I'd try to first single point partial threads, and then finish to size and proper form with the dies. Rig up some type of follower rest (wood or otherwise) and then thread between centers. That should hold it stiffly enough to permit threading, particularly for light passes.
        Lynn (Huntsville, AL)


        • #5
          Originally posted by lynnl View Post
          I don't think he's threading wood. He's threading metal to make wood hand screw clamps.

          I think I'd try to first single point partial threads, and then finish to size and proper form with the dies. Rig up some type of follower rest (wood or otherwise) and then thread between centers. That should hold it stiffly enough to permit threading, particularly for light passes.
          He said he collected wood to make the clamps😀

          If metal, then single point the threads to about 75% depth, then use your dies.


          • #6
            The wood is what the jaws are made of. He's talking about clamps such as these:
            Lynn (Huntsville, AL)


            • #7
              I think I'd try to first single point partial threads, and then finish to size and proper form with the dies.
              This is what I was going to suggest, as two other people have. The idea being that if you take only light cuts rather than try to do the entire thread to full depth on the lathe, you can get away without using a steady rest. After you have any reasonable amount of thread cut at all, the die will follow that, and because the die does not have to remove so much material is is much easier to do manually.
              "A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979


              • #8
                Your Approach doing it in the lathe is a good one , do not desert it
                The rod breaking in the middle tells me you have a bad die.
                Buy a good die , like a OSG
                Make sure it has a adjusting screw to set thread diameter and is a split die , and try it on a known bolt to compare diameter settings

                Then do this , using power feed ..
                Set the Lathe to the correct thread ( ie. 16 Pitch) but do not engage the half nuts !
                mount the die at the end of the jaws ( close to you ) and clamp it
                do your rod set up and feed it into the die . Once you have threaded maybe 1/2 inch , stop the lathe
                , now, engage the half nut (still power off) and loosen the jaws, and hold the handwheel to put drag on the the carriage.
                Now start and stop the lathe for say 2-3 revolutions. When it stops, the die will be in time with the threading setup.
                Now tighten the jaws ( the die should not be recessed about .200 to .400 in the jaws) on the die and turn on power ( Halfnut still engaged !)
                You will not power thread for your desired length . WHen you reach that length , stop , disengage Threading half nut and then reverse to clear the die fully.

                Two things, make sure you start the thread on the die with the die markings ( ie Mfg) facing you - Die front
                Two , you did not mention material for the rod , so I am assuming you just got 3/8" rod from a hardware store...that may be crap ??
                Get some 12L14 rod if you can amd maybe your old die will work with that ?

                Green Bay, WI


                • #9
                  Make yourself up one of these, put it in the tailstock, the work in the lathe chuck and do it up tight. Find a bit of round stock that fits in the chuck key slot nicely, or use a spanner on the jaws. Lock the die holder in place with the die holder arms resting on the compound and turn the chuck back and forth. May take a while but you do get a nice thread.

                  Alternatively, cut a thread on the lathe and finish off with the die.

                  Use bright machining steel, not black rod. Use a split die with it opened up as wide as possible. You can cut the first 25mm or so on the lathe to get the thread straight, then transfer the job to a vice and hand held die holder with the split die opened up as far as possible, slowly closing the die up with successive runs. I threaded these 6mm x 45mm threads this way. There was a 3mm hole through the centre.

                  Takes time, but!
                  Attached Files


                  • #10
                    Rich had some good advice. Additionally, with a good quality adjustable die, you might try first opening the die using the adjustment screw, Open as much as you dare, not breaking the die!. Then run your thread. after all the rods are threaded "oversize" , adjust for the proper size and run again. Always use good cutting oil.
                    Also mic the rod stock, it might be oversize. Which by the way will be a problem even if its "on size" , ie normally when die threading its best to have stock a few thousands under size. Measure a few hardware bolts and see, I'll bet that your 3/8 bolt measures about 0.368 - 0.370 or so. For what you are doing , you don't need or want a tight full thread, just a nice loose running fit, so that you can spin those parallel clamps. AND get some 12L14 steel, like Rich said.

                    Joe B


                    • #11
                      lynn's approach is practical. Then there is just threading in the lathe with a die stock; not the way to make a new lead screw for ultimate lathe build, but you can get a usable result. I don't like the die held in the 3 jaw for a few reasons. Dies are hard and will easily slip in the three, so you end up torquing like crazy and that could close in the die making it tight on the work, even with an adjustment screw. Things broke either because of that it was a crap/dull die (crap dies are meant to hold the garbage pail down)

                      I'd probably go with joining via silver solder (brazing) two piece of threaded rod. Its not fussy work or work where high accuracy is needed....and its a lot of threading so a low cost off shelf solution makes sense. If you didn't have a the capability of brazing, make a small union in the middle, thread each into it and loctite. Make the union short enough it doesn't foul the nuts in the clamp pieces.
                      Last edited by Mcgyver; 09-22-2021, 06:35 AM.
                      located in Toronto Ontario


                      • #12
                        Dan, you said you fed the rod by feel through the turning die. Just to clarify, you were backing off and clearing the swarf from the die regularly weren't you? Like every half turn?
                        Location: Saskatoon, Saskatchewan, Canada


                        • #13
                          I'm overwhelmed with the responses. Thank you, gentlemen.

                          Yes, it's unknown metal in 8' lengths from a web supplier. It does look much better than hardware store stuff and it threads nicely in short runs by hand. The LH die is part of an ALPS set I bought from across the little pond and being inexperienced in metal work I didn't notice an important detail. Turns out to be BSW thread type. It is a split round die for cutting new threads, not a rethreading hex die and I was careful to start it with the appropriate side, but it doesn't cut nearly as nicely as a trusty old Little Giant RH 3/8-16 RH. So it is likely as one of you pointed out to be a die weak in quality. My holder of choice was a hex stock with only one set screw and it's likely that, like holding in a 3 jaw, it compressed the die. The threads I did cut run smoothly in the mating dowel pin threaded with the matching tap from the set. Thank you for pointing that out. I have a smaller stock for 1" round that has three set screws, one of which holds the die open against the pressure of the other two. So there might be hope for that setup.

                          The notion of cutting partial threads on the lathe between centers and finishing with the die is a brilliant suggestion, a method that completely escaped my thought processes! It is certainly doable and I will try it.

                          I had dismissed the notion of making the screws in two parts joined in the middle because I have never seen LH all thread. It really exists? I could easily weld two pieces together and turn the weld down. I very much like the idea and if I can locate the requisite all thread, I'll do that. I didn't get enough material to finish the job because my math is bad, I guess, so nothing wasted to get all thread to finish. The issue might be that the all thread will be UNC and my dowels have BSW form. They should be compatible enough to work, yes?

                          Arcane post showed up while writing this. You overestimate my metal working skills! Yes, I fed the rod through machine driven die by hand turning carriage feed to match the cutting action, something my lathe is capable of, but I didn't have enough nerve to use. The die seemed to be clearing the chips adequately because it was successful for 8 of the 9 1/2" run. I was getting impatient and upped the speed and that lead to the "catastrophe". Probably as you pointed out because the chips weren't clearing fast enough and jammed. Made me lose my nerve to repeat with changes....

                          The wooden jaws will be beautiful when finished. They are red oak rafter cutoffs that I found stacked in a metal rain barrel and had been soaking there for some unknown time. They are through and through black from the tannin reaction with the steel barrel. I made one hand screw with wooden threads (all RH) and it was beautiful under an oil finish. The wooden threads were its weakness. I don't have enough of that black wood to make handles for these, so what to do has not been fully decided. Whatever wood, they will be London pattern to match all the other wood working tool handles in my shop.

                          I try to keep an open mind to useful methods when I approach a project and God only knows how long I've thought about getting this done, but I know it's been over 30 years! It's time....and I need the clamps!

                          Thanks again.

                          I'll report back in a week or so to show progress in pictures.
                          Last edited by Dan Krager; 09-22-2021, 07:05 AM.


                          • #14
                            Most hand screws I have are ACME threaded. One approach to doing this would be to purchase RH and LH ACME All-Thread and weld/pin the two parts together. This would be far easier for a novice that trying to single point a long thread. Where I live, a steel thread will rust in no time, so I would use a stainless variety of All-Thread.


                            • #15
                              Lucky, lucky people! I could grow old and die here in the UK trying to source small quantities of stainless left hand and right hand Acme allthread, but to you guys its no problem at all.
                              'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger