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2MT, 3MT, R8 ??? a newbie

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  • 2MT, 3MT, R8 ??? a newbie

    Can someone explain how and why these are different, and why one might be better than the other? I'm a little confused.


  • #2
    Morse Tapers are generally a drill press taper, meant for infrequent removal, and often without a drawbar. R8 is meant for mills with a drawbar, and is easier to knock out than a MT.

    My mill drill has an MT3, so I mount an ER32 collet chuck with a drawbar to make for easy tooling change.
    Location: Jersey City NJ USA


    • #3
      Morse Tapers: zero thru Five. Small lathes and D.P.s have 2 or 3 spindles. MT3 is sometimes used instead of r8.
      r8: Collets for milling machines- straight and taper. Not self holding. For shanked or collets with drawbar.

      5C: work holding collets that go larger than 1 inch (forget how much larger)
      3C: Mini 5c for small machines. Holds half-inch.
      ER-number: Wide range, collapsing collets. A complete set of collets holds ANY size even weird ones. For work and tool holding

      NMTB, Cat-number, 30, 40, 50, 60:

      Milling machine taper mainly for horizontals and CNC machines.
      Last edited by Teenage_Machinist; 01-22-2009, 09:07 PM.


      • #4
        OK, so I'm considering the HF Micro Mill which has MT2. Why do some frown on MT2?



        • #5
          Wonder if Sportandmiah is thinking of buying a milling machine ...

          and is wondering what's the best choice of machine ..

          then you get a different set of answers ..

          like cost verses availability and function of collets

          or availability of tooling.

          all the best.markj


          • #6
            Let me rephrase, why do some thing MT3 is better than MT2?


            • #7
              Let me rephrase, why do some think MT3 is better than MT2? Is the MT3 bigger, more useful? I seriously have no idea.


              • #8
                MT3 is bigger

                MT3 tells me that the MT3 machine is bigger and capable of turning bigger tools than the MT2 machine. My Grizzly 3n1 has an MT3 Mill Taper, MT3 Lathe Taper, and an MT2 Tail stock taper. I use an ER style collet holder that has an MT3 shank on it to do my milling.

                "When it comes to paradigms ... shifts happen" - Alain Rossman


                • #9
                  They all work. The Morse tapers were invented, I assume, by the Morse Twist Drill Co., and as others have said are often used in drill presses to hold Morse taper shank drills. They also frequently appear in lathe spindles and tailstocks to hold live and dead centers and drill chuck arbors. Morse tapers are shallow enough of an angle to be "self-holding" tapers; if a Morse taper is put into a socket, it locks and has to be pried or driven out.

                  There are also Morse taper collets. #2 Morse collets go up to 1/2" capacity. #3 Morse goes up to 3/4" capacity. Collets require a drawbar for closure. Because of the self-holding taper, one has to loosen, then tap, the drawbar to free a collet.

                  The R8 taper was invented, I think, by Bridgeport for its milling machine. The R8 taper is barely self-holding; an R8 collet or arbor needs to be tapped to free it, but it's a steeper angle than the Morse tapers and needs less persuasion. Capacity of R8 goes up to, I think, 7/8".

                  R8 is probably "better" for a milling machine, but there have been all sorts of very good milling machines made with Morse taper spindles. I wouldn't be too dogmatic about it. You can get tooling for any of them.
                  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


                  • #10
                    MT3, by itself, is not better or worse than MT2. The only issue is that it might be more difficult to find mill tooling for an MT2 spindle. MT3 is considerabley harder to find tooling for than R8 and MT2 is probably harder to find than MT3. On the other hand, for a mini mill, you won't be running very large endmills, facemills, boring heads, etc. You probably would only need a few end mill holders and a drill chuck.

                    Edit: I agree with SGW but wanted to add that you can get R8 up to 1" (maybe larger) but they are sorta goofy looking. I don't think they hold quite as well, either.

                    Edit: Here's one on ebay:
                    Last edited by Fasttrack; 01-22-2009, 09:33 PM.


                    • #11
                      Yes MT3 is bigger and will hold larger tools than the MT2.

                      However R-8 will on a mill give you a much wider selection of tooling and usually at a lower price.

                      I bought a mini-mill and chose the HF unit over Grizzly since it had an R-8 spindle and the Grizzly didn't.By doing this I could use all my existing R-8 tooling from my other mill.
                      I just need one more tool,just one!


                      • #12
                        There are other considerations...

                        The mt2, mt3, r8, 5cm, etc are specs for the spindle and the matching shaft (arbor).

                        An mt collet or an R8 collet is generally integrated with the shaft, so the size of the spindle bore will determine the maximum sized tool that will fit in the collet.

                        Any tool sold for an R8 arbor is available for an MT arbor or a threaded arbor. There are many, many sources for threaded arbors with an MT tapered shank.

                        MT taper tools are sometimes more expensive. I think that might be because the MT taper has a larger surface area that touches the mating bore, and it has to be polished and concentric along the length. The R8 taper is much less exacting.

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

                        Location: SF East Bay.


                        • #13
                          in toolholding featires (spindle taper in this case0 biger is alway better. MT3 iis bigger then MT2 (0.700 and 0.937 respectively) therefore stiffer. R-8 is 1 1/4 on the big end therefore stiffer. None of these can be considered all purpose milling machine taper tooling. They have limited rigidity and torque transmission. #30 milling taper hase about the same taper dimensions as the R-8 but since it also has a keyed flange its torque drive is positive. Larger millint tapers are even more rigid.

                          However the spindle configiration is governed by the machine's scale and Morse and R-8 spindle are selected for smaller machines where cost, small size, and convenience are primary considerations.

                          That said, many smaller jig borer spindle are Morse taper. Sine precision repeat location are primary considerations andjig borers are seldomg used for any but finishing operations at very high precision. Everything has advantages and disadvantages.


                          • #14
                            Thank you to all, a lot of good info for the slow learner (me). One last question: could the micro be changed to accept a MT3 or R8?


                            • #15
                              I can answer this one.

                              Technically, you could rebuild the head with a different spindle.

                              Realistically, You would not want to. You would have to replace a lot of major parts and rework a bunch of others. You'd need a machine shop to do it.

                              The mt2 taper is not a problem for a micro-mill. The mill's motor and gears will not handle big tools. Look at the owners manual to see the maximum size end mill and drill size.

                              A lot of tools come in a straight shank that will fit in a collet. The set of fly cutters I bought for my micro-mill have a 1/2 inch diameter shank that fits well in a 1/2 inch mt2 collet.

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

                              Location: SF East Bay.