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Tangential toolholders evovling in my shop

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  • Tangential toolholders evovling in my shop

    I'd been reading about the tangential lathe tool in different places on the internet, so decided to give it a try last year. Like so many others, I came up with a simple design and went for it. Here's what that looks like:






    I was immediately impressed with the ease of sharpening and the finish that I was able to achieve with the tangential tool holder. So, I could see that it was worth the trouble. . . . But, there were a couple of problems.

    1) My original design required me to make a bolt to hold the toolbit in place. I chose to put fine-thread on it thinking that it would hold the bit tighter with less effort than would be required by coarse thread. Problem was, it was easy to over-tighten and destroy the bolt



    I tried making a coarse-thread replacement, but the replacement suffered the same fate! I finally replaced with grade 8 button-head bolt, and that held. Note that I never have experienced any problems with the bit slipping down in it's slot--it was just over-torquing it that was the issue (clumsy bastard!).

    2) There was not enough clearance to face large parts. The bolt that holds the toolbit does not allow for turning and facing of pieces larger than 1 1/2" or 1 3/4" without the bolt rubbing against the workpiece. This is really a show-stopper as part of the allure of the tangential toolholder is the ability to face and turn without repositioning the holder. Without this ability it will always be "less than". . . .

    3) Design of toolholder will not allow it to work equally well when facing a deep slot at the "tailstock end" as it does at the "chuck end" of the work piece. There's just too much metal extending to the right of the toolbit. No getting around it with this design.

    more to come!
    Last edited by Jim2; 05-23-2013, 02:43 PM. Reason: misspelling in title

  • #2
    Round 2

    This time 'round, I wanted to be sure that it would turn and face without any limitations from the toolbit clamping mechanism. I wanted something simple and durable in case the mechanism broke, so that it could be easily replaced. I wanted to be sure the toolbit would be held tightly in the slot. This is what I came up with:






    That's a chunk of metal there--1 1/2" wide x 1 3/4 high at it's largest point. The "half-moon" holder is 1" diameter, W1 toolsteel. I figured that I could harden it if it showed any signs of wear or weakness, and it would be easy to replace. Yeah, that extra radius running vertically was a mistake. . . . I figure no reason to try to cover it up. There was plenty of metal to get the job done anyway.

    This version didn't have any of the annoying problems with interference when turning and facing--no repositioning of the tool required! It might have been "good enough", but for the fact that the first thing I tried it out on was one of those dumb little projects where you do something because you can, not because it is necessarily a good idea. I needed to take a piece of 10" piece of 1/2" shaft down to 7/16". So, I get a center in the end of the piece, slide it out of the collet, tighten it up, set up the tailstock, and. . . . Whoa this toolholder is huge! Getting the tool holder even close to the live center is going to be a real pain. This is actually the moment when the third "requirement" from the other post started to form in my mind.

    There has to be a better way, so it's back to Google images. . . .

    Comment


    • #3
      Originally posted by Jim2 View Post
      ...<snip>...

      Yeah, that extra radius running vertically was a mistake. . . . I figure no reason to try to cover it up. There was plenty of metal to get the job done anyway.

      ...<snip>...
      This is a very interesting thread. I have often wondered if I could make a tangential holder.

      I find the remark about an "extra radius running vertically" I quoted a bit confusing. Exactly what radius are you referring to?

      I also fail to see why the nose area of the holder needs to be so wide. The bit is constrained at the front by a relatively thin wedge of metal that is, perhaps 1/8" or even 1/16" thick at the top. So why is almost a full inch of metal needed to the side? It would seem that the front wedge of metal takes most of the clamping force as well as the force generated while cutting. The metal to the side of the tool would be under less stress. Perhaps this thickness to the side could be cut in half or even less. Perhaps as little as 1/4" would suffice.
      Last edited by Paul Alciatore; 05-23-2013, 02:18 PM.
      Paul A.
      SE Texas

      Make it fit.
      You can't win and there IS a penalty for trying!

      Comment


      • #4
        No 3

        There have been a couple of toolholders on other forums that I took most of my inspiration on No 3. One fellow in particular had come up with a clever way of drilling a hole in his toolholder and then silver-soldering a piece of shaft in there that had been split down it's center with a square cross-section machined into it. He had done such a nice job that it was difficult to tell how he'd made that nice square hole! Anyway, this is what I did:










        I know lotsa milling marks on the toolholder. Meh, I kinda like it! I was in a class, and they had one of those triangular insert face-mills. It gets plenty of use and abuse from all of us noobs in there, so no doubt may have been cutting on just one insert? But, I was still impressed with its metal-moving capability. I don't have carbide at home, and this thing was taking off 3 times as much each pass of anything else that I had tried (toolholder is A2 toolsteel). The smooth portions of the shank were done with my 7" Porter-Cable shaper. I'm a noob on that, too. This and No 2 above were really the first times that I'd had a chance to get my feet wet with it. I have to say it's great fun for a hobbyist like me. I wouldn't want to try to make money with it, though.

        I'll follow up with a drawing if anyone is curious about dimensions.

        Jim

        Comment


        • #5
          @Paul:

          Yeah, it could be narrowed down a bit, no doubt. It's quite a chunk of metal. There's no reason that it has to be that thick. The reason that I designed it that way (1 1/2" wide) is so that it could be angled properly to work with my primitive, lantern-style toolpost, and still have the clearance necessary to do the turning and facing without repositioning. Stock on the right side would have to be removed to satisfy those requirements.

          I'm not going to lose too much sleep over it, because No 3 is a better design, IMO.

          Here's the drawing of No 3



          Jim

          Comment


          • #6
            Originally posted by Paul Alciatore View Post
            This is a very interesting thread. I have often wondered if I could make a tangential holder.

            I find the remark about an "extra radius running vertically" I quoted a bit confusing. Exactly what radius are you referring to?
            Thanks, Paul.

            I'm referring to the radius where the narrow part of the shank meets the thicker portion. You can see it better here:



            It was just one of those dumb little math errors. I forgot to subtract out the radius of the hole I was drilling, but NBD in this case.

            Jim

            Comment


            • #7
              Jim,
              In version #3 did you use a milling cutter to cut the square slot for the toolholder; or did you use the shaper?

              Cheers,
              Norman

              Comment


              • #8
                I used a slitting saw to get it close, then cleaned it up with a 3/16 end mill. I'm sure the end mill would have done the whole job, no problem.

                Jim

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                • #9
                  Thanks for posting this interesting project, what drawing program are you using (for drawing in post #5)?

                  Comment


                  • #10
                    Jim,

                    All of those tangential holders are awesome.

                    I couldn't help but notice your collet chuck. Is that one of your own creations as well? I ask because I have a Sheldon 10" lathe with a 1 3/4", 8 TPI spindle that's extremely non-standard with respect to today's available commercial tooling. I'm considering turning my own ER40 chuck and thought I'd get some advice from you or anyone else reading this post. I hope I'm not hijacking this thread.... again.... just awesome tooling on your part.

                    Johnny

                    Comment


                    • #11
                      Originally posted by dfw5914 View Post
                      Thanks for posting this interesting project, what drawing program are you using (for drawing in post #5)?
                      I'm using Google Sketchup. I never used any kind of 3D drawing program before, but the tutorials make it pretty easy to get started. I wouldn't say it's easy, but persistence seems to pay off eventually. Put it this way--the tool is capable even when the user isn't!



                      Originally posted by Johnnyreich View Post
                      Jim,

                      All of those tangential holders are awesome.

                      I couldn't help but notice your collet chuck. Is that one of your own creations as well? I ask because I have a Sheldon 10" lathe with a 1 3/4", 8 TPI spindle that's extremely non-standard with respect to today's available commercial tooling. I'm considering turning my own ER40 chuck and thought I'd get some advice from you or anyone else reading this post. I hope I'm not hijacking this thread.... again.... just awesome tooling on your part.

                      Johnny
                      Yes, I did make up the collet holder for the lathe. My Leblonde is quite old, a 1924. . . . It's been a few years now since I did it. I think the taper was messed up in there. Anyway I cleaned it up a bit. It's basically a MT 5 now. It has a 1 3/8" ID spindle, so 5c works pretty well with it. The version you're looking at is actually round 2 on that as well. I made a handwheel-style tube in Round 1, and that worked pretty well. Here's a pic




                      The problem with that was that the internal thread that engages the 5c collets eventually stripped out. I hadn't done many internal threads prior to making the tube, so they weren't maybe the best. Then there is the way the headstock is designed. As you can see it was difficult to get something that would accomodate the belt-drive there. At that time I didn't have the guard on the belt because the closer was in the way. It was definitely a hazard, but that end of the lathe was back in a corner--still not good. When we moved to the new house, something had to be done. The lathe was set up in the middle of a big garage, and I couldn't be sure that my kids wouldn't show up and get tangled up in that belt. Something had to be done. . . .

                      Please look away if cutting up classic machine tools/guards makes you queasy




                      Round 2, includes the addition of the big nut on the end. I use the handwheel to engage the full length of the thread on the 5c collet, then tighten the big nut to tighten the workpiece in the collet. The handwheel is keyed to the tube, but is free to slide along it. I think this arrangement may help to preserve the lifespan of the threads. It's been working this way for me for quite some time now. Notice the extra length that will be used when those threads eventually fail on the collet end.

                      Jim

                      Comment


                      • #12
                        Jim, #3 is a nifty design, and your implementation looks "sturdy" to put it mildly. Nicely done.


                        Just for the sake of discussion, could the "vise" end of the holder be reconceptualized as a two-piece affair, coupled with three or four clamping screws, thus eliminating the long slot for those without the horsepower or slotting saw to fabricate such?

                        Comment


                        • #13
                          Seems to me a well guided hacksaw or bandsaw would work for those of us lacking the ability to use large slotters...

                          Comment


                          • #14
                            Thanks, tlfamm. adatesman has it figured out. The slot doesn't need to be as wide as I made it. A hacksaw or a bandsaw would do the job just fine. For me, part of the elegance of the design is that it's all made from one piece of steel. It was also much easier to make than the other designs because it doesn't have any of those confusing compound angles.

                            Jim

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                            • #15
                              how did you make the rectangular slots, the tool sits in (in the last holder)? using the shaper? but how?

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