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  • ? on the mechanics of a quick change tool post

    My next project is going to be a quick change tool post. I have done google
    searches and read all I can find on making one. Since I have never seen one
    in person I have a question. On the commercial types the main body is made of
    three pieces (not counting the T or the bolt). The square body with the dove tails, a cam and a center the bolt goes down through and the cam rotates around. My question is this, do you have to loosen the center bolt that secures the tool to the compound before you can loosen the cam and change a tool holder? If so, doesn't that make it difficult to secure a new holder with the whole thing trying to spin?
    Also approximately how deep are the dove tails. For me its going to be all a
    3/4" dove tail mill will cut. Will .002 - .005 per pass be ok for a HSS dove tail mill in mild steel?
    Thanks.

  • #2
    The center nut clamps the body to the top slide, and the handle does the cam for the tool holder, so you can change the holders without the body moving around.

    cheers,
    Michael

    Comment


    • #3
      I think that .002 - .005 per pass would be fine for a finishing cut. Depending on the rigidity of the machine & setup you can go a lot deeper. You need to use a slow speed and slow feed, and coolant helps.

      The cut below was done in 3 passes. Material is mild steel and the cutter HSS. First and second cut about 0.100" deep then 0.010" on the finish cut. After the initial cut I dropped the table by 0.002" as these cutters can chatter when they cut on both the bottom and sides at the same time, then put it back after the finish cut for a clean-up pass. Coolant applied by hand with a squeezy bottle.
      Also, don't climb mill with a dovetail cutter (except on a 0.002" finish pass maybe ) as they will *really* suck into the cut.





      Peter

      Edited to Add: John Stevenson designed a quick change toolpost some years ago. Theres a link to it here where there are drawings that will give you a idea of size for dovetails etc. http://www.metalwebnews.com/howto/to.../toolpost.html
      Last edited by Peter N; 08-12-2006, 01:36 PM.

      Comment


      • #4
        In lieu of the possible difficulties in making the dovetail, consider making a T-slot arrangement. This would involve cutting slots in the body with a regular end mill (instead of the dovetail) and making a couple of corresponding ears on the slides. The end result is the same, you are locking the slide to the body but the cam action is against a 90 degree shoulder instead of a dovetail.

        Comment


        • #5
          Originally posted by Michael Moore
          The center nut clamps the body to the top slide, and the handle does the cam for the tool holder, so you can change the holders without the body moving around.

          cheers,
          Michael
          I can't get it in my head how the center nut can camp the body with a cam in between the two able to move. Am I making this too difficult?
          If I could only get my hands on one!
          Thanks for the replys.

          Comment


          • #6
            qc

            Bill, there is a description with drawings for a QC Toolholder by Rudy Kouhoupt in the The Shop Wisdom by Rudy ... volume4. This QC is relatively simple. The other suggestion is to take up the offer somebody gave you above. Look at those drawings and you will learn a lot from there. To make an exact copy of the PhaseII QC or Aloris would be rather difficult for you, I think. Good luck!Vic

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            • #7
              I made this rear mounted post to hold a KDK parting tool holder. I am not sure if the front one is actually a KDK. The handle rotates the dovetail to lock it against the tool holder.

              Comment


              • #8
                Here's a poor picture of how the wedges fit in the toolpost I made.



                One passes thru the other.
                The nice thing about this design is that it's not critical on the dove tail tolerances.
                I have a couple that are loose by about 20 thou but they still tighten and hold position.

                Some designs you have to be dead on for the locking mechanisms to work or they are out of travel.

                .
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                Comment


                • #9
                  link to QCTP

                  http://homepage3.nifty.com/homeshop-...ctp/qctp-e.htm This link will get you picures of a piston type tool post, should give you a good idea of how they work. The fellow has several interesting pieces of
                  tooling with step by step notes and photos of how he made them.
                  Last edited by J Harp; 08-12-2006, 08:41 PM. Reason: correction
                  Jim

                  Comment


                  • #10
                    If you want to consider a different design, here is the one I made. It does not use any dovetails but has all the operational advantages of of the dovetail design. The flat on the central post does the indexing so you can exchange tools and keep your settings. And each setting, tool height, angle, etc. is independent of the others so it is easy to adjust in use.





                    The only feature not apparent in the pictures is the 45* cut on the holders is machined with the side where the hold down screw goes is about 0.010 lower than the other to provide clearance for tightening.

                    I have written an article describing it's construction and submitted it to the mags. I don't know if they will ever publish it. I guess the dovetail holders are more sexy. But in my humble opinion, this one is a lot more solid. It does use more metal for each tool holder.

                    Paul A.
                    Paul A.
                    SE Texas

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

                    Comment


                    • #11
                      The John Stevenson design is great, it's easy to make, cost efficient, and does not require any hardening or heat treatment.


                      Regards GRH

                      Comment


                      • #12
                        Paul, that design looks very solid, and that's what counts. Hellova job.

                        Comment


                        • #13
                          Originally posted by GRH
                          The John Stevenson design is great, it's easy to make, cost efficient, and does not require any hardening or heat treatment.


                          Regards GRH
                          Thank you George,
                          The cheques in the post

                          .
                          .

                          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                          Comment


                          • #14
                            Sorry John, must have missed out on your toolpost. Won't happen again!

                            Comment


                            • #15
                              Originally posted by Millman
                              Paul, that design looks very solid, and that's what counts. Hellova job.
                              Thanks. It's like one solid block of metal on top of the compound. And tool changes are very fast with no tools and only one hand required. No heat treatement and no dovetails. The bore is done on the lathe and since I have a separate boring bar holder I use the center post as the check gauge. Centering is not critical in this operation and can be off by hundreths with little effect on the utility of the holder. All in all, additional holders are quick and easy to make.

                              I have also made a couple of cutoff tool holders since the pictures were taken. They really add stability to that operation.
                              Paul A.
                              SE Texas

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

                              Comment

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