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Where do tapers come from?

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  • Where do tapers come from?

    Is there any rhyme or reason in the Morse and B&S taper families? Do the various tapers correspond to known ratios of integers, or are they just plain arbitrary (i.e., Joe made the first one, and we've been making them that way ever since)?

  • #2
    The stork brings them.
    Free software for calculating bolt circles and similar: Click Here


    • #3
      well a mommy taper and a daddy taper get together and .....

      Matt in AK
      Matt in AK


      • #4
        My understanding is that tapers of a given degree will "hold" in a tapered socket of that same degree. Too little or too many degrees and the holding character is lost. Somewhere in one of my books this is explained in mind-numbing detail. I have put this to use in making a carriage-clamp for my lathe - I wanted the handle to "cling" to the bolt and so I used (if I remember correctly) a taper of about six or seven degrees with male/female parts having the same corresponding taper. I believe the Morse Taper preceded the B&S and that the B&S was designed primarily with milling rather than drilling in mind.


        • #5
          Since the morse tapers were all supposed to be the same.....but they ain' be the judge.

          Story has it that the measuring wan't done right, either due to tools, or whatever.....

          In any case, they differ a small amount. This is likely due to their being made originally as actual units. If made as mathematical descriptions, they could have been improved as measuring got better.

          Personally, I wish the Jarno had won out. All same taper per unit length, mathematical description.

          [This message has been edited by J Tiers (edited 02-04-2005).]

          Keep eye on ball.
          Hashim Khan


          • #6
            what about the Jarno taper? my tool & die teacher, an old Westinghouse journeyman, swore by it as the best...jim


            • #7
              Yes, could never figure why the angle is different from morse no. to morse no. The jarno makes the most sense, same angle from number to number, (I'm thinking .600 per foot taper?) From a manufacuring stand point who would want to deal with all the angle set-up changes?

              [This message has been edited by egpace (edited 02-04-2005).]
              Ed Pacenka


              • #8
                This taper lark is simpler than you suppose.

                A No2 Morse taper is formed by a sine of 10 inches and a quarter of an inch.

                What more is there to be said?

                Geordie Boy


                • #9

                  Do you mean a 1/4 inch rise on a 10 inch sine bar? If so, that's good for the No. 2, but how about the others?



                  • #10
                    There's two kinds of tapers in common use in the machine shop: self-holding and self-releasing.

                    Morse was the first with the most popular so it became the de-facto standard; not too consistant or well chosen perhaps but standard. Considering that Morse made his first taper gages in 1853 or so and the worst taper in the series was within 0.005" per foot of the mark I think he did very well. Imagine his available resources in 1853(?) and be amazed at the quality of his work.

                    Since the Morse tapers are based on his gages instead of the mathematical model of 5/8" per foot we're stuck with what we have: an imperfect system that's worked very well for 150 years and happens to be a world standard.

                    Brown and Sharp tapers 1/2" per foot were the defacto self-holding standard for end milling cutters and milling accessories until the Weldon shank came along. This taper worked well when properly fitted and driven solidly home but as the taper wore they'd self-eject. If you've ever run B&S taper tooling in a worn out spindle you'll appreciate the speed of its replacement by the presently used and practical setscrew/straight shank milling cutters.

                    The Jarno system is indeed a well designed self holding taper series but alas it never caught on. Too bad, but it lost like Sony BetaMax and Apple computer.

                    A world standard for self-releasing taper is the milling machine taper in common use today. It's 7/24 taper (3 1/2" per foot) is used even in lathe spindle noses. This series ranges from tiny to huge ant its principles features have been standardized. Only a few of these standard milling taper (with varients) are in common use. The most common milling machine taper in the US is that described ANSI B5.18. This has a retention stub extending from the small end of the taper tapped to receive the drawbolt.

                    Since they are face keyed and secured with a drawbolt, this is a very stiff and reliable retention and registration system for rotating tooling. The driving capacity of flanged self-releasing spindle tooling limited only by the mechanical strength of its parts.

                    Varients of this self releasing system of spindle tooling have beed adapted for use in CNC tool changers. The stub has been eliminated and the drawbolt hole inthe small end has been taken over by the tooling retention knob, (BT and Cat taper) and the flange provided with a precision registration feature to suit modern tool changing and storage mechinisms.

                    Like lawyering, ours is a messy business based on precident enshringing in tradition the lame and awkward leaving superior methods and practices to wither in museums.

                    That's just how it is. The purists can complain but our present system of tapers and toolign registration standards is bigger even than city hall. Even the Commies used them during the Cold War.

                    [This message has been edited by Forrest Addy (edited 02-04-2005).]


                    • #11
                      Forrest that really cleared up a lot of questions about how tapers came about, thanks...
                      My question is when they say 5/8" per foot is that talking about the rise from the center of the shaft or the included angle of both the top and bottom of the shaft?
                      I hope I explained my question right...
                      I never could figure that out...


                      • #12

                        If you have a 12" long rod 1" dia. on one end and the opposite is 1 5/8" dia, then you have a 5/8" per foot taper on that shaft.


                        • #13

                          Excellent expalnation on the 7/24 tapers (NST, BT & Cat flange) - however in high precision machines the HSK-63 is the stiffest and most accurate taper available today - even if it is weird looking...


                          • #14
                            hay I learned something today thanks for the explenation sounds better than mine
                            Matt in AK


                            • #15
                              Poorly setup lathes.

                              Paul A.
                              Paul A.

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