Morse taper spec.

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Morse taper spec.

Home Forums General Questions Morse taper spec.

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  • #355325
    Maurice Cox 1
    Participant
      @mauricecox1

      I have just turned my first morse tapers; some plugs for the centre of a rotary table. In the process, I refered to the Model Engineers handbook to see what sort of angle I was looking for. I found that there was no reference to degrees, but taper per inch on diameter. Fair enough, but why are they all different tapers? I could understand if the taper increased (or decreased) with an increase in diameter, but they don’t, and the diference is sometimes as small as five, one hundred thousandths of an inch! Can somebody explain the thinking behind these specifications please?

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      #26000
      Maurice Cox 1
      Participant
        @mauricecox1
        #355327
        richardandtracy
        Participant
          @richardandtracy

          If there was any deep thought about it – which looking at the numbers I too doubt – I reckon it's lost in the mists of time.

          The tan of the angle is close to the coefficient of friction for steel on steel. It's possible different sizes were made and tested on different days, with different levels of oil contamination on the different days, so the test house determining the angles found fractionally different ones each time. That sort of design by testing went on at the company I work for when I joined it 30 years ago, and led to similarly bizzare results. All changed now, I may add.

          Regards

          Richard.

          #355348
          Chris Evans 6
          Participant
            @chrisevans6

            ARC euro trade catalogue has the tapers listed "for reference". Set your top slide with a sine bar and you are good to go.

            #355353
            Howard Lewis
            Participant
              @howardlewis46836

              Morse Tapers vary from one size to the next *WHY did we not use nthe Jarno which is constant for all sizes?)

              The only angle that I can recall is 2 degrees 52 minutes for 2MT.

              Given the taper per inch, some simple trigonometry should allow the angle to be calculated.

              Although I wouldn't fancy my chances of setting the Topslide over one degree 26 minutes!

              Using another MT of the same size as a setting master, or Sine Bar and Slips would be my choice.

              Howard

              #355359
              Maurice Cox 1
              Participant
                @mauricecox1

                My question was not really about how to set the correct angle, it was really about why each size seems to vary erratically by tiny amounts from one size to the next. It seems to make no sense!

                Maurice

                #355364
                Clive Hartland
                Participant
                  @clivehartland94829

                  If I need an MT for something I set up the MT between centers and adjust the top slide with a Dti parallel to the taper.

                  It works for me.

                  #355365
                  Nick Hulme
                  Participant
                    @nickhulme30114
                    Posted by Maurice on 25/05/2018 22:12:09:

                    My question was not really about how to set the correct angle, it was really about why each size seems to vary erratically by tiny amounts from one size to the next. It seems to make no sense!

                    Maurice

                    Why does the sun come up in the morning? Are the stars just pin holes in the curtain of night?

                    Like all other random engineering stuff it was decided before there was anyone to indulge in debating the reasons on the internet leaving us with the choice to deal with it or use something else 😀

                    #355369
                    John Reese
                    Participant
                      @johnreese12848

                      I believe Morse tapers originated before accurate means of measuring the angles were commonly available. They were made to match master gauges for each taper. The master gauges were intended to be 5/8" per foot taper on the diameter. They did not get the taper exactly right on the masters.

                      #355390
                      Michael Gilligan
                      Participant
                        @michaelgilligan61133

                        Posted by John Reese on 25/05/2018 23:35:21:

                        I believe Morse tapers originated before accurate means of measuring the angles were commonly available. They were made to match master gauges for each taper. The master gauges were intended to be 5/8" per foot taper on the diameter. They did not get the taper exactly right on the masters.

                        .

                        I can't find the details, but I'm pretty sure I have seen the discrepancy explained as a 'rounding error' in the method used to set the angles when the Masters were created.

                        This is worth a look: **LINK**

                        https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3779551/pdf/264_2013_Article_1927.pdf

                        MichaelG.

                        #355393
                        larry phelan 1
                        Participant
                          @larryphelan1

                          Sparey remarked in his day about the Jarno system,which made more sense,but never came into common use.

                          Why ? Good question,but no answers ! Could be like some of the decisions arrived at by Co Counsels, in that there is no logic to it,and you are not supposed to understand it,just accept it.

                          #355400
                          Neil Lickfold
                          Participant
                            @neillickfold44316

                            I was looking into this recently.

                            Found this note interesting.

                            A question often asked within the clinical community is, “what specifically is a Morse taper and can it provide a stable connection between components?” A Morse taper is defined by the angle that the taper surfaces make relative to the longitudinal axis of the component and by the mismatch angle between the male and female part. The original Morse taper angle defined by Stephen Morse for tools was a relatively small angle of 2° 50′, with the mathematical relation that tang 2° 50 = 5 %.

                            Neil

                            #355402
                            SillyOldDuffer
                            Moderator
                              @sillyoldduffer

                              The question has come up before and no-one seems to know.

                              As the tapers are precision made I'm confident that the odd angles are deliberate, not an accidental by-product of the way they were machined or calculated.

                              My guess is that Morse deliberately used a variety of slightly strange angles as a way of detecting patent infringements. At the time quick change tools were an important innovation and the Morse company would want to protect their idea for as long as possible. A Morse taper cannot be independently reinvented; anything to those specs not made by Morse must be a copy, and I think it would be easy to convince a court that the patent was infringed.

                              Accidental by-products do occur in measurements. Careful analysis of the dimensions of the Pyramids seem to prove conclusively that the Ancient Egyptians must have calculated an accurate value for π, 3.14159… This is a serious shocker, because it means their mathematical methods must have been far more advanced than other evidence suggests. Actually π emerges from the data because the Egyptians often measured distances with a device like a surveyors road wheel. And wheels naturally come with π, it's not a design requirement. π in Ancient Egypt is coincidence, not genius.

                              Dave

                              #355403
                              Michael Gilligan
                              Participant
                                @michaelgilligan61133
                                Posted by Neil Lickfold on 26/05/2018 09:40:59:

                                I was looking into this recently.

                                Found this note interesting. [ … ]

                                .

                                Me too, Neil … Which is why I wrote that the paper was 'worth a look' rather than being 'authoritative'

                                MichaelG.

                                .

                                I suppose this is the most important statement in it:

                                … Morse created the taper shank series. Two sets of master gages were made up; one, sent to the Bureau of Standards in Washington, D.C., was accepted as a National Standard. The other remains with the Morse Company.

                                .

                                International Orthopaedics (SICOT) (2013) 37:2081–2088

                                Edited By Michael Gilligan on 26/05/2018 09:51:51

                                #355421
                                Ian S C
                                Participant
                                  @iansc

                                  There is an article in #26 MEW Nov / Dec 94, " Self Holding Taper Sockets" by Alan Jeeves.

                                  Ian S C

                                  #355427
                                  John Haine
                                  Participant
                                    @johnhaine32865

                                    Though interesting, I'm not sure that it's very significant. If they were "rational", it wouldn't be any easier to make them would it?

                                    #355429
                                    richardandtracy
                                    Participant
                                      @richardandtracy

                                      It would only need one setup on the machine for different tapers, though. Many machines have different tapers at the head and tailstock, and need to make bits for both. It would make it easier to use the same setup.

                                      Regards,

                                      Richard.

                                      #355432
                                      Georgineer
                                      Participant
                                        @georgineer

                                        I read somewhere, a long time ago and I can't remember where, that the angles were purposely made different so that male and female tapers of different sizes couldn't be wedged together with resulting difficulties in separating them.

                                        George

                                        #355433
                                        Georgineer
                                        Participant
                                          @georgineer
                                          Posted by SillyOldDuffer on 26/05/2018 09:48:20:

                                          Accidental by-products do occur in measurements. Careful analysis of the dimensions of the Pyramids seem to prove conclusively that the Ancient Egyptians must have calculated an accurate value for π, 3.14159… This is a serious shocker, because it means their mathematical methods must have been far more advanced than other evidence suggests. Actually π emerges from the data because the Egyptians often measured distances with a device like a surveyors road wheel. And wheels naturally come with π, it's not a design requirement. π in Ancient Egypt is coincidence, not genius.

                                          Dave

                                          Magnus Pyke, in one of his wonderful radio talks, said that Charles Piazzi Smyth, the eminent Victorian astronomer, made a series of detailed measurements of the pyramids, and concluded that the builders had used the God-given inch as their unit of length, not the atheistic French metre.

                                          George

                                          #355445
                                          Neil Lickfold
                                          Participant
                                            @neillickfold44316
                                            Posted by Georgineer on 26/05/2018 12:23:26:

                                            I read somewhere, a long time ago and I can't remember where, that the angles were purposely made different so that male and female tapers of different sizes couldn't be wedged together with resulting difficulties in separating them.

                                            George

                                            This is correct. I can't find the reference for when I made some MT2 and MT4 tapers recently, but the spec was given as a diameter at one end, and a diameter at the other end, and the length of the distance apart of these 2 dimensions. The part that I found was interesting was the tolerance specified on the taper. The outside part could be made to the same taper, with the small end, could be made smaller by 0.0001 inches. The inside taper on the small end could be made bigger by 0.0001 inches. This difference would make then jam/wedge tight together. There was also mention to the reason for the sleeve extension outside of the sleeve, as an area to yield when the smaller sleeve is inserted and drifted to position.

                                            Neil

                                            #355454
                                            Pete Rimmer
                                            Participant
                                              @peterimmer30576

                                              I've yet to hear and tales of woe of anyone getting Jarno tapers wedged in such a fashion, and they are all made the same angle of taper.

                                              #355458
                                              Michael Gilligan
                                              Participant
                                                @michaelgilligan61133
                                                Posted by Neil Lickfold on 26/05/2018 13:24:57:

                                                Posted by Georgineer on 26/05/2018 12:23:26:

                                                I read somewhere, a long time ago and I can't remember where, that the angles were purposely made different so that male and female tapers of different sizes couldn't be wedged together with resulting difficulties in separating them.

                                                George

                                                This is correct. I can't find the reference …

                                                .

                                                Footnote 47, on p57, here [?] :

                                                https://books.google.co.uk/books?id=F8jtCwAAQBAJ&pg=PA57&lpg=PA57&dq=morse+taper,+metrology&source=bl&ots=BqKPWUOhBN&sig=BYWM2lRezho2_e4A3oCWjKgnD9U&hl=en&sa=X&ved=2ahUKEwit5fDvxqPbAhWEAcAKHTuuARMQ6AEwAnoECAIQAQ#v=onepage&q=morse%20taper%2C%20metrology&f=false

                                                MichaelG.

                                                **LINK**

                                                #355485
                                                Neil Wyatt
                                                Moderator
                                                  @neilwyatt
                                                  Posted by Georgineer on 26/05/2018 12:23:26:

                                                  I read somewhere, a long time ago and I can't remember where, that the angles were purposely made different so that male and female tapers of different sizes couldn't be wedged together with resulting difficulties in separating them.

                                                  George

                                                  Disproven easily, I'm afraid – try fitting MT tapers in the wrong socket. Either they won't fit in or they will rattle like a stick in a bucket – the size differences are too large.

                                                  And if they did fit, would they be more likely to stick then the matching taper?

                                                  The B-series chuck tapers are interesting.

                                                  Neil

                                                  #355520
                                                  Georgineer
                                                  Participant
                                                    @georgineer

                                                    Pete – Jarno tapers weren't published until 25-odd years after Morse tapers, and we know that engineering moved on a lot in that time. Besides, who can say what bees designers have in their bonnets? I know I have made allowances in designs for things which turned out not to be a problem, and I'm sure a lot of others on this forum have done exactly the same.

                                                    Michael – Interesting footnote, but it doesn't cover the reasons for the difference

                                                    Neil – It looks as though your comment proves the point, as in neither case does the wrong Morse taper cause problems by jamming…

                                                    George

                                                    #355536
                                                    John Haine
                                                    Participant
                                                      @johnhaine32865
                                                      Posted by richardandtracy on 26/05/2018 12:09:02:

                                                      It would only need one setup on the machine for different tapers, though. Many machines have different tapers at the head and tailstock, and need to make bits for both. It would make it easier to use the same setup.

                                                      Regards,

                                                      Richard.

                                                      That's true if you decide to have a taper-making session, but in my experience I either have to make one for the tailstock (MT2) or headstock (MT4, shortened). Anyway, it's just a different set of parameters for the taper turning wizard!

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