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  • single point threading tools

    Of late I have been doing more single point threading than I usually do and so am grinding tools to suit. It strikes me as highly wasteful to grind away a large amount of say a 1/2" square piece of tool steel, just to produce a 60 degree point for a 26 tpi thread. Using this size blank is also a pain when threading up to a shoulder as the tool can get in the way. Has anyone had any success with another method?
    I've seen but never tried disc type form cutters whick might be a better way to do things. The other one that I did try was a parting tool ground to the appropriate geometry (I 'inherited' one ground that way with some secondhand tooling). While easy to grind, the tip flexes side to side too much to give me great confidence in the result (it might work with a custom holder perhaps)
    Another option I suppose is carbide inserts but the cost of doing that makes a HSS solution much more attractive.

    Michael

  • #2
    Threading Tool

    Use a 1/4 or 5/16 HSS bit and grind the point off center mostly to the left side. That will get you right up next to a shoulder with a lot less grinding.

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    • #3
      As mentioned by toolguy, smaller tool bits ( 3/16, 1/4 etc.) work well. I have ground several at an angle so as to be able to direct the tool from the best direction. The smallest I have turned successfully is 2-56. I am still using the Atlas 10 inch lathe.
      Jim

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      • #4
        Eh, Try using a zirconium 36grit belt + 21x3" or so belt sander
        secure the bit in a vise, and use lots of pressure. Grinds metal off REAL quick. Basicly end up with HSS wool afterwards. Have a spray bottle or something to cool the HSS every few seconds.

        Also as people mentioned, grinding them to one side makes it much easyer to thread to a shoulder
        I usally only leave about 1/8" or less on the left. Or when its an 'upside down' bit, on the right. (See: Threading away from a shoulder)

        Also, while you can use smaller bits, Might I recommend trying a rectangle bit? Like the 1/2" by 1/4" bits, they can be easily ground into slim tools while still having a nice tall height and lots of rigidity.

        An angle grinder with an abrasive cutoff disk can kinda be used to rough a bit.. but its tricky not to overheat the bit, Don't do it anywhere near the cutting edge... Can also use a standard angle grinder disk to 'gouge' out areas to rough the form.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #5
          Unscrewed-up

          Originally posted by form_change
          Of late I have been doing more single point threading than I usually do and so am grinding tools to suit. It strikes me as highly wasteful to grind away a large amount of say a 1/2" square piece of tool steel, just to produce a 60 degree point for a 26 tpi thread. Using this size blank is also a pain when threading up to a shoulder as the tool can get in the way. Has anyone had any success with another method?
          I've seen but never tried disc type form cutters whick might be a better way to do things. The other one that I did try was a parting tool ground to the appropriate geometry (I 'inherited' one ground that way with some secondhand tooling). While easy to grind, the tip flexes side to side too much to give me great confidence in the result (it might work with a custom holder perhaps)
          Another option I suppose is carbide inserts but the cost of doing that makes a HSS solution much more attractive.

          Michael
          Michael.

          Why screw-thread TO a shoulder? Why not screw FROM it?

          In other words either have the lathe running forward with the tool inverted (up-side down) and to the back of /behind the job or alternatively with the tool inverted and to the front to the job with the lathe in reverse?

          Keep the "vee" as far to the left as you reasonably can to give yourself the maximum "wriggle room".

          The size of the tool-bit is pretty well irrelevant - use 1/4" square HSS.

          Machine a "starting groove" near the shoulder and start the screw cut from there and exit the cut near(er) the tail-stock.

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          • #6
            I've been able to find full boxes of NOS MoMax 5/16, and good quantity of 3/16-3/8 good name brand HSS in a variety of grades for VERY good prices (cheaper than Enco Chinese). Like you, I see no real need to grind away at huge blanks, so I mostly use bits in the 3/16 to 5/16 range. However, in a 3/4" CXA holder that can be a bit problematic. So I took some scrap 1/2" and 3/4" square and plate scrap (think key stock) and milled the corners/sides out to fit the smaller HSS bits in such a way that it is fully supported near the top of the 3/4" CXA slot, but still clamped by the holder screws. I've got a few big pieces with common roughing profiles ground in, but generally if I'm looking for something that big, I'm reaching for my CNMG or TNMG 43n tooling..

            BTW, another nice thing about using smaller bits in larger blocks, it's easy to mount 2 in a singe block! For instance, one of my most common use tools is a single holder setup to cut both OD and ID 45* chamfers. Both sides are 5/16 MoMax, setting on one of those "packing" bars. When mounted on the far side of the CXA post, the bit toward the spindle cuts (and clearanced for) a 45* chamfer inside a hole. The tip is small enough to cut a small chamfer on the near side inside holes down to about 1/8" dia hole, but further back it's well supported and can cut a fully 1/8 chamfer in a larger bore. When mounted on the left of the post, the tool on the far side (from me) is used to cut chamfers up to near 1/4 on the near/right side of a shoulder. One block, 2 of the most common tools used, and using high quality yet inexpensive and easily ground bits. I've got similar setups for other common "form" bits such as radius, fillet, etc.
            Russ
            Master Floor Sweeper

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            • #7
              I have 20 or so threading tools mostly for 60 degree threads, many with different offsets, tip truncations etc. Once you get a collecton you never have to modify them, merely touch them up as needed.

              Sooner or later a lathe owner gets smert and lays in a supply of HSS tool blanks and grinds up a mess of standard tools. Spread out I probably have two square feet of HSS tools but that's a many year collection.

              Hm. Come to think of it, I started my apprenticehip July 10, 1961. So 49 years but who's counting.
              Last edited by Forrest Addy; 09-05-2010, 01:57 AM.

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              • #8
                Originally posted by Forrest Addy
                I have 20 or so threading tools mostly for 60 degree threads, many with different offsets, tip truncations etc. Once you get a collecton you never have to modify them, merely touch them up as needed.

                Sooner or later a lathe owner gets smert and lays in a supply of HSS tool blanks and grinds up a mess of standard tools. Spread out I probably have two square feet of HSS tools but that's a many year collection.

                Hm. Come to think of it, I started my apprenticehip July 10, 1961. So 49 years but who's counting.

                Do we get bragging rights for starting an apprenticeship earlier?? (Jan 7 1955)

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                • #9
                  Not so long-a-go

                  Oct/Nov 52.

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                  • #10
                    Other threading tools

                    Other single-point threading tools:

                    crochet hook:


                    from:
                    http://en.wikipedia.org/wiki/Crochet_hook

                    and a button hook:


                    from:
                    http://en.wikipedia.org/wiki/Button_hook

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                    • #11
                      May 2006? (when I signed up here)

                      As for getting a collection, you can accelerate by doing what I do/did. Many times I go to an auction, there are boxes of HSS, usually grouped loosely by size (and nothing else). I get these boxes of HSS blanks, often for $5 to $10. They are full of a wealth of bits, generally ground by "pros", and on good blanks. Those I can figure out and find suitable, are added to my "ready" collection. Others I can only ponder what the heck they were trying to do, or simply figure I have no use, and these get reground as needed.
                      Russ
                      Master Floor Sweeper

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                      • #12
                        Originally posted by form_change
                        ...It strikes me as highly wasteful to grind away a large amount of say a 1/2" square piece of tool steel, just to produce a 60 degree point for a 26 tpi thread. Using this size blank is also a pain when threading up to a shoulder as the tool can get in the way...
                        The old British writers in Model Engineer had a fondness for ROUND HSS bits in a simple holder for small threads. Minimal grinding required; easy to make a grinding jig; bit can be rotated to follow the lead angle for coarse (or left hand) stuff; if the mounting hole is angled, altering the projection of the bit adjusts it for centre height.

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                        • #13
                          Small screwing tools

                          You are pretty right djc.

                          Round HSS bits are easy to use and are not all that expensive - and they can be as small as required.

                          I have several - one type that can be rotated as you say - pic at end of this post - what is basically a boring bar holder.The difference here is that I need only grind off the top face and then lift the tool to centre-height. It is pretty smart but the principle is obvious. The pic also shows parting off tools by the same maker.



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                          • #14
                            "v"

                            I forgot to say in my previous thread, that a round HSS tool can be held in the tool-post just as well by use of a steel (any) block with a machined "V" on the top face - say 100>120*. Rest the HSS tool in the "V" and clamp it with the tool-post or adaptor clamping screws as normal.

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                            • #15
                              Thanks guys. BadDog's suggestion of holders for smaller bits of tools steel sounds most appropriate for me (I'm running BXA holders myself). Like BD and a couple of others I have a collection of bits (mainly 1/2") that I got from a toolroom clean out at a company that ran cam auto lathes making hose fittings. I'll have to keep my eye out for smaller stuff. I have occasionally used snapped drill bits for cutting tools, so that's worth revisiting too.
                              Anyone got any good ideas for holders for internal ACME thread cutting? I'm currently using a boring bar with a HSS insert ground to shape but is there a better way?

                              Michael

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