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  • R8 Question

    NooB here...........

    Are all R8 shank arbors the same? I see ones on Ebay that say Bridgeport, yet are some other manufacture.

    I have an old Rockwell mill I am slowly gathering tooling for.

    Thanks, Dennis

  • #2
    R8 Tooling

    All R8 tooling is theoretically the same. The only difference is in the quality of manufacture or degree of care or abuse. I have a lot of R8 tooling and it all works fine. I don't buy any used tooling unless it looks really good. There are a lot of collets and shanks that have been tightened down on chips or spun in the spindle or rusty etc.
    Kansas City area

    Comment


    • #3
      I'll say they are all the same. When holding an end mill in the collet they are at best a compromise. If I had a nickel for every operator that had an end mill suck out of an R-8 collet I'd be a rich man.
      Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

      Comment


      • #4
        Not to hijack Dennis' post, but I've got a popular 3/8" R8 collet with a piece
        of broken endmill in it.

        Like spin says, at some point it walked its way out and snapped. Theres
        maybe 1/2" of it trapped in that no-mans-land between the threads and
        the collet ID. Have been using it find, but bothers me that its in there.

        Any tricks to getting it out? lost cause?

        Tony

        Comment


        • #5
          R8 Collet

          Hi Tony -

          Get a round magnet 3/8 or smaller that will slide into the threaded end of the collet. Get the piece of shank on the magnet and lined up with the hole and pull it out the threaded end which is bigger than 3/8. Maybe if you shake it around with the threaded end down it will fall out by itself without a magnet.
          Kansas City area

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          • #6
            Spread the collet open with screwdrivers in the three gaps should help you get the broken shank out. Obviously don't spread it too far.

            Comment


            • #7
              Originally posted by Spin Doctor
              When holding an end mill in the collet they are at best a compromise.

              Ok, here's the question again.
              If not for holding end mills, what exactly are R8 collets for??
              End mill purists will tell you that they should only be held in end mill holders.
              Drill bit purists will tell you that drill bits should only be held in drill chucks.

              That being the case, what are all those collets for??

              Comment


              • #8
                i also reckon collets are the best way of workholding. if they are hardened and if they are ground to the precision you require.

                Comment


                • #9
                  Collets

                  Collets are great for work holding and tool holding. You just have to tighten them firmly and use them correctly. In the case of pulling an endmill out of an R8, assuming a good collet with no dirt or chips in the taper, either it wasn't tight enough or the cutter was being fed into the work too hard. With a reasonable feedrate it isn't an issue. If you want to really push the cutter, you should be using a solid holder with a setscrew.
                  Kansas City area

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                  • #10
                    I've never had an end mill pull out of a collet. I do have top-quality collets (Hardinge) in good condition, which certainly helps. If you have worn or cheap collets, I think it might be different. Or if you try to take unreasonably huge hogging cuts.
                    ----------
                    Try to make a living, not a killing. -- Utah Phillips
                    Don't believe everything you know. -- Bumper sticker
                    Everybody is ignorant, only on different subjects. -- Will Rogers
                    There are lots of people who mistake their imagination for their memory. - Josh Billings
                    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                    Don't own anything you have to feed or paint. - Hood River Blackie

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                    • #11
                      Threaded endmills were invented[possibly Clarkson] to overcome the "pulling out effect" of friction type collets, they are screwed into special threaded collets and if set up correctly they cannot pull down even under a heavy cut. R8,ER etc collets rely on friction only to hold the cutter in place and can shift under a heavy cut, I have had this situation once or twice in my career. Another big difference is that with friction collets you can extend the cutter out of the collet to get more reach for deep pockets etc, this is a really useful feature which I have used many times.
                      Tony

                      Comment


                      • #12
                        Originally posted by SGW
                        I've never had an end mill pull out of a collet.
                        Me neither.
                        I've seen the telltale marks on production tables though.

                        Some things that cause trouble in a real machine shop may be trouble free at home.
                        Mike

                        My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."

                        Comment


                        • #13
                          "Some things that cause trouble in a real machine shop may be trouble free at home."

                          I'm sure. I am far from being a "real" machine shop!"
                          ----------
                          Try to make a living, not a killing. -- Utah Phillips
                          Don't believe everything you know. -- Bumper sticker
                          Everybody is ignorant, only on different subjects. -- Will Rogers
                          There are lots of people who mistake their imagination for their memory. - Josh Billings
                          Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                          Don't own anything you have to feed or paint. - Hood River Blackie

                          Comment


                          • #14
                            I had a 3/8" end mill pull out of a cheap import collet once when I first started in the hobby. I might not have had the drawbar tight enough. Anyway, since wiseing up enough to buy Royal collets, keeping the threads lubed, and tightening them well ( power drawbar helps), I have never had it happen again in the 20 years since. Keeping the endmill shanks and collet bores oil free helps as well.

                            RWO

                            Comment


                            • #15
                              Originally posted by RWO
                              I had a 3/8" end mill pull out of a cheap import collet once when I first started in the hobby. I might not have had the drawbar tight enough. Anyway, since wiseing up enough to buy Royal collets, keeping the threads lubed, and tightening them well ( power drawbar helps), I have never had it happen again in the 20 years since. Keeping the endmill shanks and collet bores oil free helps as well.

                              RWO
                              I once read a study where they actualy tested pullout strength under verious conditions.
                              IIRC, they found that lube *everywhere* was better then lube nowhere.
                              Infact I seem to recall that lube on the outside of the collet (and threads) and endmill was still better then just lube on the threads.

                              (Consider that the collet must 'slip' in the tapered section to tighten up the endmill)

                              Of course, a dry endmill with lube everywhere else was better then an endmill coated in oil, but my point was given the choice you should oil the collets, even if it might leak onto the endmill.
                              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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