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  • Eccentric Clamps

    Decided to make some eccentric clamps to match der operator.

    Got a job in from a well know aero engine maker who wishes to remain anonymous but has RR in the name.

    Three bars with pegs to go into holes that act like a simple 3 jaw chuck to hold a turbine blade in the crack detection tank, nothing critical, no flight safety crap and you can put any non ferrous metal into these tanks.

    However this anonymous company decided they need these bars making out of 30shïtfacedrockhardtoolcrunchy stainless steel.

    Unfortunately this grade is only sold in sheared strip and not cold rolled with the result that [a] it's not flat, [b] the edges are rounded where it's been sheared and [c] it's the most terrible material known to man or beast and [d] it's not magnetic.

    So they want the bottom face machined flat, all over.
    No good clamping to the bed and doing it is stages as when the claps are released it will still be bent, soooooo I need to hold it by the edges whilst I mill the whole side in one go.

    Now I have seen these Mighty Bite clamps before in pictures but never in the flesh, looked them up in MSC J&L and had to lean on the battery charger to get some resuscitation back into the circuit, [ damn Lucas pacemakers ]

    Seventy freaking nine pounds each ????????????????? leastways I think each as there is no picture.

    Soooooooooo, raid the scrap box and mill 4 long tee nuts, tap for one Allen screw and one grub screw. Bit one done

    Lob a chunk of 22mm bar [ 7/8" to the metrically impaired ] in the chuck with three bits of banding under one jaw to throw it off centre, drill and ream to 5/8" to fit head of 10mm Allen screw, loctite and whack onto head of screw with large bopper. Bit two done.

    Find long U bolt nut off 32 tonne trailer, bore 22mm and part off 4 pieces. Bit 3 done.

    All bits present and correct on duty.



    Did some spare Tee nuts at the same time.

    Shot of the setup.



    Three fixed fingers at the rear, eccentric clamps at the front with some normal tee nuts to act as spacers and be lower than the top face.



    Close up of the clamp, you place the clamp, nip the grub screw to hold the tee nut into position then wind the Allen screw round and the eccentric forces the hexagon piece against the work.

    Doesn't need to be hexagon, could be square the main bit is the eccentric action.

    .
    Last edited by John Stevenson; 07-01-2009, 07:55 PM.
    .

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




  • #2
    So the eccentric locks by friction? I don't see why the eccentric doesn't release with cutting vibrations?

    If it works, it sure seems like a neat solution to a tough clamping problems.
    Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

    Comment


    • #3
      Good lick, John.

      Comment


      • #4
        Probably would come loose if you went all out to try to rip this off the table, however I have too much time invested in these arms what with the slot details that are on the underside and the rack teeth to get it too excited.

        Probably took 1/2 hour to flatten all three, took nearly two hours to make the damn clamps.

        Thinking about it it works the same way as a camlock chuck and they work out OK until you get big interrupted cuts.
        .

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



        Comment


        • #5
          Nice Work.RR will be proud

          I sprung for the "real thing" aka "Mighty Bite your wallet", but billed them
          out to the job I was doing
          Noticed that they are now copied by Phase II for about 1/3 the price
          Not sure of the quality.

          Yes they hold well up to a point and then...
          Had a nice job in the cnc mill that was about finished when
          it came loose. Came up with a few new swear lines...
          Put those in me note book as well. Never know when I my need that combi
          again.
          eddie
          please visit my webpage:
          http://motorworks88.webs.com/

          Comment


          • #6
            thats a cool clamp. nice work.

            Comment


            • #7
              Unsimplification, aka degeneration into elegance

              Originally posted by camdigger
              So the eccentric locks by friction? I don't see why the eccentric doesn't release with cutting vibrations?

              If it works, it sure seems like a neat solution to a tough clamping problems.
              I was wondering about that too. Maybe a setscrew (with brass tip)through the hex might solve the "obvious" problem. Hey - with a little effort I could make this really complicated!

              -bill

              Comment


              • #8
                eccentric clamps

                You should try some like this John. The black one is hardened steel held by a flush socket head cap screw and is tightened against the work with an angle grinder spanner as you lock it down. It can be flipped over so that vibration tends to tighten the holding screw for the tough jobs.

                Free software for calculating bolt circles and similar: Click Here

                Comment


                • #9
                  Interesting concept Evan, that's given me an idea on an improvement, mind if I pinch the basic design ?

                  .
                  .

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



                  Comment


                  • #10
                    Not at all. I'll be interested to see what you come up with.

                    To save you some time here is a DXF of the cam profile:

                    http://ixian.ca/server/camclamp_profile.dxf
                    Last edited by Evan; 07-02-2009, 09:10 AM.
                    Free software for calculating bolt circles and similar: Click Here

                    Comment


                    • #11
                      Nifty concept Evan.

                      For those of us sans CNC, it looks like a slice of round stock with a hole drilled off center could substitute for the cam. Leaves room for extra spanner holes giving more options for the handle angle while securing.

                      John
                      Location: Newtown, CT USA

                      Comment


                      • #12
                        Here's the second pic for the cdcotools system.
                        http://cdcotools.com/morepics.php?itemid=477

                        Comment


                        • #13
                          For those of us sans CNC, it looks like a slice of round stock with a hole drilled off center could substitute for the cam. Leaves room for extra spanner holes giving more options for the handle angle while securing.
                          I haven't tried it but I don't think a circular cam will work as well. I designed the spiral cam to have the clamping force vector pass through the bolt hole at all angles of rotation. This prevents the forces from moving the clamp. A circular clamp will not be in that condition except within two small arcs of it's circumference. I don't think it will stay tightened as well.

                          Free software for calculating bolt circles and similar: Click Here

                          Comment


                          • #14
                            Originally posted by rancherbill
                            Here's the second pic for the cdcotools system.
                            http://cdcotools.com/morepics.php?itemid=477
                            That's a picture of how the Mitee-Bite clamps work The cap screw is eccentric, not the hex nut.
                            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                            Comment


                            • #15
                              Evan, I like your cams. They might also lend themselves to use in a part where you could mill some slots in the side of the work so the cam could be inserted into the slot and when tightened down to the t-nut, also hold the part down as well as putting the side clamping force into the part. I've found that with the M-B clamps you've got to watch that you don't pull the part up off the table.

                              cheers,
                              Michael

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