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  • Looks like my lathe at work,it gets cleaned out when the carriage starts dragging stuff back and forth with it
    Last edited by wierdscience; 03-25-2012, 03:40 PM.
    I just need one more tool,just one!

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    • Another QCTP

      I should have made this long ago. For many years I used a shop-built indexing four-way turret style tool post on my Jet 1024 that served me very well, so I didn't have a strong incentive to do this project. But recently I mentored an 8th grader doing a school project (we made the front hub for his mountain bike) and it got me excited about doing some projects of my own again.







      The dovetail clamp is essentially John Stevenson's design, with a small refinement. Rather than a threaded stud passing through the body with a nut to close the clamp, I have a double ended screw, right hand threaded into the dovetail clamp and left hand threaded into the body, with a 3/8" hex end protruding for a wrench. (That's an idea that came from another qctp project in HSM 25 years ago.) I had planned to use an ordinary box wrench but then decided to make something prettier. I turned away most of a 3/8" socket and brazed it into the handle you see.

      I built my four-way post to index at 15° increments, and that was so useful I wanted to include that feature in the new tool post as well. You rarely see that on a dovetail type qctp, and I found that, while it's almost essential for a four-way post, it's not so important for a qctp. Still, it's a nice feature, and made it unnecessary to make the usual two-dovetail configuration, so there was some simplification there. You can see that I made four pockets in the base for spring & ball locators, but I found that one is adequate. That's why you see three empty spring pockets. Similarly, two locating dowels are enough, so there are two empty dowel holes. The base, T-nut and top handle are from the old four-way post.

      Having the two handles swing on intersecting planes isn't optimal. The handles clash more often than I anticipated, though only when the body is turned at an angle. Not a real problem, just an occasional annoyance. Still, I'd do it differently if I made another one. (Not likely, since I'm so happy with this one.)

      I have a decent start on a collection of tool holders, including a knurling tool, (I might make a second one so I have one for straight knurls and one for diamond), a dial indicator holder for setting up work in a 4-jaw chuck, and a radius turning attachment built around a boring head.

      For years I had intended to build a parting tool holder on the back side of the cross slide, since, as is often the case on a small lathe, I've found parting difficult at times. But this setup is so much more rigid than what I had before that parting is no problem at all now.

      All in all a really good project that makes the lathe much nicer to use.

      Comment


      • Very nice work, Randy - does the dovetail match commercial holders, just in case?

        I think the indexing feature's an excellent improvement, I'm always getting customers moaning that their new QCTP doesn't have it! Does the index plate with the ball/spring/dowels have a key for the topslide slot to hold it in its orientation?

        I may try to mod the QCTP I have for the indexing feature, but I'd probably leave out the dowels, as I sometimes want just a touch of angular freedom (when squaring up a parting blade, f'rinstance) - maybe putting the ball/spring in the T-nut, and the recesses in the bottom of the QCTP?

        Dave H. (the other one)
        Rules are for the obedience of fools, and the guidance of wise men.

        Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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        • Agreed nice workmanship, looks very good! Thanks for posting that!

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          • Re: Another QCTP

            Dave,
            Not made to be compatible with commercial holders. I wasn't concerned with that. I designed it according to what I wanted and materials I had at hand.

            It's not very clear from the photos that the center screw is made from a long 5/8" set screw with a hex socket at the top. Tightening the center screw with an Allen wrench secures the base ring to the top slide. The base ring is not keyed to the T-slot, so that's where I get my fine angular adjustment. Once the base ring is secure, turning the main lever allows the body to rise up and turn to other index positions. The base ring stays in place so the index positions are pretty repeatable. The dowels are essential to locate the body securely and repeatably. The spring/ball just provides tactile feedback and holds the body enough to keep it in line with the dowels while it's being lowered by the main lever.

            Comment


            • Ah! Makes sense (I think) now!

              So... (Dumb Questions follow...)

              For an Aloris-style post, I'd need to recess the base for the ring and drill (e.g.) 24 holes on the dowels' PCD;
              bore a short way for the "lifting" spring between 'post and ring;
              clamp the ring with dowels and balls/springs with the centre stud;
              tighten the post down on that with the existing top nut, locating the dowels in holes in the recess...

              A bit of angular adjustment could be put on by loosening the central stud where it pulls up on the T-nut in the topslide, allowing the ring to rotate on the topslide...

              Once the ring's pulled down/T-nut's pulled up by Allen key in the centre stud, loosening the top nut (handle on your 'post) allows the 'post to rise off the dowels by spring/ball pressure, allowing 15-degree indexing...?

              Is that about how it works, or have I got it wrong *again*???

              Dave H. (the other one)
              Rules are for the obedience of fools, and the guidance of wise men.

              Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

              Comment


              • Hi Randy,
                Just One More Thing... (Tm. Lt. Columbo)

                I *think* I have it worked out, apart from the base ring - how is/are the ball/s and springs held in place, or do they spring out and cause a lot of grovelling on the floor for the unwary? It looks like the base ring's made in two (or more) parts, are the balls and springs sandwiched between the two, with smaller-than-ball-diameter (countersunk from below?) holes through the top plate? If so, I guess the balls are larger in radius than the dowels' height, so they ride up above the top of the dowels and engage the indexes during rotation?

                I think I can do the necessary steps, I have a rotary table and can bolt it to the drill press for the indexing holes etc. - depends whether the toolpost's hard right through!

                Thanks again, I've been inspired to try it myself!

                Dave H. (the other one)
                Rules are for the obedience of fools, and the guidance of wise men.

                Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

                Comment


                • Re: Another QCTP

                  Yes, Dave. You've got it pretty well figured out. My base ring is one piece. It looks like two because there's an o-ring around it to keep debris out. (Overkill, probably. This project was inspired in part by catalog photos of a Royal tool post, which has an o-ring there.) The ball is not captive, and will fall out of place if the body is raised too much. One turn of the main lever will raise the body .090" (on an 11tpi screw), just clearing the dowels without allowing the ¼" ball to come out of its pocket. It's not fool-proof like a commercial unit needs to be, but it works well for me. Sorry for the slow response. Good luck with your project.

                  Comment


                  • so i was experimenting with my home made moglice and i poured it into the nut around the shaft. i wanted to check the stick slipp, so i made an other shaft 0.08 mm oversize and pressed it into the bushing. no stick whatsoever, extremely smoth rotation, im very satisfied.

                    anyways, because it worked so well and it happened to be the right size, i put a dremmel thread on it and made myself a little spindexer. it also holds small drills for grinding. just flipping it around gets the other edge right. btw, i find they work quite well with only one edge of 10° on them.

                    http://i973.photobucket.com/albums/a...ndian/x064.jpg

                    i might mill/grind the nut true to the axis, but it really doesnt make sense, because the little dremel chuck has a runnout of 0.1 mm. i might try the proxxon collets (8 x 0.5 mm) in the future, they look more promissing (steel).
                    Last edited by dian; 04-22-2012, 01:52 PM.

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                    • Originally posted by dian
                      so i was experimenting with my home made moglice and i poured it into the nut around the shaft.
                      Can you tell us more about your home made moglice? What recipe did you use? Did you have problems finding the ingredients etc...

                      bob

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                      • Seconded.... I want to hear the recipe as well.

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                        • well, its a big secret, but im going to tell you anyway. i take it to general.

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                          • Roller Project

                            Here is a project I would like to share, a few years ago my machining class built this as a class project...

                            They designed and created, and it works well!


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                            • Marty that is a very good looking piece of work.

                              (got a kick out of your'e signature line!!)

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                              • check out the 2012 N.A.M.E.S. thread

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