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  • QCTP questions before I build.

    I want to build a QCTP. That said I’ve been looking at many of the plans out there. I want two mounts. The top will tighten the mount, lower to lock the quick mounts. There is a wedge type, pin type, and pin with flats on it.

    So on to my questions:
    What is the best way to lock the quick mount? Wedge type, Pin type, or Pin with flats on it. (If there are others … Please post.
    If you know of a good set of plans to start from please post. I still have not seen how the wedge style works so one of those plans would be great!

    I know I can buy one of these but then this would not be a hobby.

  • #2
    The wedge type is generally considered superior because it allows you to remove a tool and pot it back on more precisely than a piston style. This is because the wedge pushes the holder into the edge of the dovetail. A piston style holder pushes the holder out , so the location is based on beveled edges of the dovetails.

    In general, a cheap QCTP will get you within a few thousandths of an inch when you put the tool back on.


    I used a piston style on my smaller lathe and have no problems with it, but I always check the alignment of everything when I change tools.


    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

    Comment


    • #3
      I have one of each and have not noticed much difference in performance when changing tools. The smaller one is a Dorian and on my 9X20, the AXA size is on my 40's vintage Logan. Both seem ok to me. I once had a Harbor Freight QCTP which worked also worked fairly well. The HF unit is really simple and is basically a "wedge" type. Bob.

      Comment


      • #4
        Ok so here the next big question??? AXA size Is ther A double D? What are the sizes? The size of the dove tail hight range of the tool rest???

        Maybe I'll build the taper jig first. I think I have the plan for that.

        Comment


        • #5
          I have a "cheap and dirty" piston type, but am in the process of building a "split dovetail" type. This will follow the design sold as a casting kit by Andy Lofquist at Metal Lathe Accessories. His design uses a different size tool block from the "standard" designs, and i want to have ALL my tool blocks interchageable betwee both lathes.
          essentially, his design uses only one locking handle. It first locates the tool on the compound, and then, with more torque, locks the assembly. This is achieved by forcing a tapered, (self-releasing,) plug downwards to cause the sides of the dovetail to spread and lock the tool holder. The clearance between dovetail and tool holder is only a few thou, so a slight turn on the handle locks pretty securely.
          I am building from scratch and the only bit that matters is the taperd plug, which is recommended to be cast iron.
          This design appeared in one of either HSM or MW waaaay back.
          Building your own tool blocks is a mugs game. It is generally agreed on this site that you cant buy the raw material for the price of a finished tool block, ($8.00-$10.00!)
          Duffy, Gatineau, Quebec

          Comment


          • #6
            Originally posted by outlawspeeder View Post
            Ok so here the next big question??? AXA size Is ther A double D? What are the sizes? The size of the dove tail hight range of the tool rest???

            Maybe I'll build the taper jig first. I think I have the plan for that.
            The size that matters for the tool holders is the height of the cutting edge above the top of the compound. Look at the following link for the dimensions.
            http://www.industrydepot.com/DorianToolToolHolders.htm

            Consider the following for a small 9 inch lathe; Assume there is 7 inches swing over the saddle, but the compound has a raised spot for the tool post. The distance from the top of the compound to the center of the chuck is only 1.5 inches. That means that the total height of the tool and the 'A' dimension of the tool holder must be less than 1.5 inches when added together.

            Dan
            At the end of the project, there is a profound difference between spare parts and extra parts.

            Comment


            • #7
              If you are going to make one, you may want to consider an alternative design. This is mine and it has some advantages over the standard dovetail design.



              One advantage is it's basically a two piece construction: the post and the holder. This makes it rock solid because when the holder is attached to the post there is 360 degree contact between them making it virtually a single, solid piece of steel. Far more solid than the limited contact provided by a dovetail design.

              The flat on the post serves as an indexing reference. It is a lot broader than some round post designs that use a slot and pin for indexing. This provides very good repeatability when the holders are interchanged. I have measured better than 0.001".

              Another advantage is you can change holders with one hand in a single motion. Just grab the holder by the handle of the adjustable nut and drop it on the post. A quick rotation of that handle and you are done. No tools needed. You don't even have to shift your hand from the holder to the locking lever. Removal is equally easy and fast.

              Adjustments of the tool position are easy and they do not interact with each other. A tool can be repositioned in the holder without changing the angle or height. Height changes do not change angle or position. Etc. This makes adjustments in use very easy.

              The dimensions can be scaled to fit almost any lathe.

              Of course, it does not use the commercially available, dovetail style holders.

              This photo shows the various parts.



              Ignore the SS SHCS shown for locking the tool bits down. I replaced them with grade 8 SHCS shortly after the photo was taken due to flattening of the tips under pressure.

              The construction was published in the Feb-Mar 2010 issue of Machinist Workshop. Or if you PM me I can e-mail you a copy.
              Last edited by Paul Alciatore; 11-17-2012, 02:43 AM.
              Paul A.
              SE Texas

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

              Comment


              • #8
                Hi outlawspeeder I have just built a variation of the MLA toolholder and I am pleased with the outcome. I does not index because I do not do much repetition work, it locks both the toolblock and at the dovetail with just a slight tightening of the central handle. I have fitted it to a new topslide (compound) for my Chipmaster lathe. The plan was to minimise the cantilevered overhang of the toolholder.




                Alan

                Comment


                • #9
                  Homemade quick change

                  Below is a quick change AXA post I made. The toolholders are locked in place with a 1/4-20 SHCS. I used it for 5 or 6 years then bought a Aloris toolpost. It is simple and easy to make.









                  Here it is again on my Denford/Orac CNC lathe. I came up with a speed handle for tightening the toolholders.
                  with handle

                  Jim
                  Last edited by outback; 11-17-2012, 07:30 PM. Reason: Added CNC lathe
                  So much to learn, so little time

                  Comment


                  • #10
                    Originally posted by outlawspeeder View Post
                    I want to build a QCTP. That said I’ve been looking at many of the plans out there. I want two mounts. The top will tighten the mount, lower to lock the quick mounts. There is a wedge type, pin type, and pin with flats on it.

                    So on to my questions:
                    What is the best way to lock the quick mount? Wedge type, Pin type, or Pin with flats on it. (If there are others … Please post.
                    If you know of a good set of plans to start from please post. I still have not seen how the wedge style works so one of those plans would be great!

                    I know I can buy one of these but then this would not be a hobby.

                    The Omni Post type would be a good starting point for "rolling your own". Stone ax simple, rugged design that could be easily scaled to the size of your particular lathe.

                    http://krfcompany.com/


                    Rex

                    Comment


                    • #11
                      Outback I like that one. I would like to put a handle on it to make it Quick. Jackary, that is a very clean look. Paul Alciatore I like the it but there is not a up/down adj.

                      I am still looking but have started to pull from the best of what I see.

                      Comment


                      • #12
                        My post DOES have an "up/down" adjust (tool height). It is a bit hard to see in the photos because the screw is recessed. If you look at the tool holder that is standing on edge in the rear of the second photo, you can see the adjustment screw sticking out of the bottom, next to the "D" shaped hole for the post.

                        It is easily adjustable from the top and since it uses friction (fishing line in the threads) to hold the adjustment there is no locking nut and no backlash when adjusting it. Simply dial it in and re-lock the holder on the post. Fast, easy, and accurate. Far easier than the height adjustment on the "standard" dovetail holders which can change in height when the adjustment is locked down.

                        All in all, I did put a lot of thought into the design and I believe it is better than most that I have seen.


                        Originally posted by outlawspeeder View Post
                        Outback I like that one. I would like to put a handle on it to make it Quick. Jackary, that is a very clean look. Paul Alciatore I like the it but there is not a up/down adj.

                        I am still looking but have started to pull from the best of what I see.
                        Last edited by Paul Alciatore; 11-18-2012, 01:03 AM.
                        Paul A.
                        SE Texas

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

                        Comment


                        • #13
                          Originally posted by Paul Alciatore View Post
                          One advantage is it's basically a two piece construction: the post and the holder. This makes it rock solid because when the holder is attached to the post there is 360 degree contact between them making it virtually a single, solid piece of steel. Far more solid than the limited contact provided by a dovetail design.
                          Unfortunately Paul I must disagree based on three points. 1. The two piece construction of your toolholder itself is a major source of flex that the standard Aloris style doesnt have, 2. if your toolholder is adjusted upward you lose much of any rigidity you had due to flex of the rather skinny toolpost itself, and 3. the small diameter of the spacer that the toolholder sits on. If you look at a typical QCTP, the main "block" of the post sits directly on the compound and typically makes for a nice wide base for the post itself, without this base needing to have any vertical adjustment. If the spacer between the post and the holder was a much larger diameter and the toolholder itself was one piece with a simple large screw to clamp it, it would be close to the rigidity of the dovetail QCTPs, but then repeatability comes into play and you would very likely be fighting a losing battle.

                          I do applaud your efforts at trying to create a better tool tho. Always gotta try for a better mouse trap.
                          "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

                          Comment


                          • #14
                            It might take some searching, but there was a design similar to Outback,s where a round "piston" ran thru the dovetails, locking via a thru-bolts like his does. You cut the dovetails w/ piston in place (bolted tight w/ washer under them. Seemed quick, simple & solid to me. Easily made to standard dimensions to use standard tool blocks.

                            uute

                            Comment


                            • #15
                              Originally posted by jackary View Post


                              All of that looks beautiful! I assume you made the compound as well? Very nice job!


                              My first project on the lathe when I got it was to make a QCTP. I made the entire thing on the 10" atlas with also using a milling attachment. Piston type, not sure on exact repeatability of the tool (never checked) I just set the tools once and forget about the setting. Haven't had any trouble with anything yet.



                              Andy

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