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Setting Tapers

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  • Setting Tapers

    As a full time jobbing shop engineer anything I can do to speed the job up helps me no end.
    People who often see these setups remark that they aren't in any books so I think it helps to share.
    Today I did a new No2 morse extension holder for a guy and I had to explain how I set the taper.
    Normally according to books you either set the compound by using an existing taper as a master and clock it in using a DTI or you use the DTI to get an offset reading along a known length.
    Invariably you have to polish up and blue to get a good fit.
    This is the method I have used for many years and it's quick and simple. It's based on the master principle so you will need a good taper to follow.

    [1] Set the compound to zero. If you do this once with a DTI following a parallel test bar in the chuck and examine the marks under a good magnifing glass you can use this mark in future and not bother with the DTI again.
    [2] Mount a piece of parallel bar in the chuck or if you have just done [1] above with a DTI, leave the bar in.
    [3] Mount a piece of flat bar in the toolpost sticking out like a boring bar. The middle of the bar needs to be roughly on centre hight. A lathe tool reversed makes a good bar if it's straight.
    [4] Either spin the toolpost or adjust the bar so that it lies parallel to the test bar. A sheet of white paper underneath helps to spot any errors.
    Lock the tool and toolpost.
    [5] Mount a good taper between centres or chuck and support in the tailstock centre.
    [6] Slacken the compound off and offer the toolbar up to the taper. Adjust the compound so that the bar lies parallel to the taper and lock the compound off.
    [7] That's it job done and set. No DTI and it's quick and simple. It actually takes longer to write this than do it.
    Hope this helps someone.

    John S.


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

  • #2
    Sounds good John! I like your common sense, practical way of doing things - keep em coming...


    • #3

      I can verify that this system works well. I happened to make a new top slide for my lathe and in the process made sure the dovetail for the top slide was true to the outer edge (the edge nearest the work when in the normal 90* position). I then made a template setting plate (using gauge plate) which bolts to this true edge. The template is right angled at the top and knife edged to be 'on centre' ~ to do a Morse taper just requres the mounting of the setting plate, slack the compound slide, bring it up alongside a master taper, clamp up compound, and Hey Presto ~ it works really well!

      It's also good for doing 1 in ? tapers as I have mrked it acordingly at suitble metric and imperial positions, to place gauge pins, to give me the right taper relationship. Example: for a 1:48 taper (1/4" per foot) over 2" requires gauge pins differing by 0.0208" on diameter.


      [This message has been edited by Ragarsed Raglan (edited 11-17-2002).]


      • #4
        I use that method when I can. My Maximat 7 does not have a long slide on the compound and this only works for JT's and short MT's. My compound does not have the linear range for a MT#2. As such I have to set the tailstock over and use ball centers. This also produces a taper that does not require grinding, filing, or touching up.

        That is the price you pay when have no space for a bigger (gorilla sized) machine.


        • #5
          Ever think of writing a book?
          "The Wisdom of John Stevenson"
          PS The name Stevenson is a common name in my home town.(see my web page for link)


          please visit my webpage:


          • #6
            I don't think I could do it under this title as I had my wisdom teeth out years ago

            I have seen you web page before. We both use the same model TOS lathe. Fancy buyng a new one?
            Have a look at
            Pick lathes and scroll down to the SN50
            Not a bad price for this amount of metal.

            John S.

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


            • #7
              Hi John
              That SN 50 works out to 21,000 canadian!!
              That is a good deal.
              I paid more than that 5 years ago!?
              please visit my webpage:


              • #8
                I have to admit, I'm not convinced...if you have the original taper set up between centres, or whatever, why not just set the compound by running a DTI up and down the taper? This gets everything right in one setting. Maybe your method is quicker? but I can't see how it would be as accurate, which would be my first concern on say a MT.


                • #9
                  First off it won't be as accurate as using a DTI. I did imply that in my first post.
                  What it will be is quicker and cheaper for the guy starting up who wants to make some extra equipment and doesn't own a DTI as yet.

                  My experiance has shown that you need to polish to a blued finish on a MT taper anyway so using this method saves time setting a DTI up.
                  The slightest error on any taper will produce errors when blued up.

                  This leads up to a question I don't really want to follow as it will quickly get off topic, but.........
                  How do you know the MT taper on your machine is EXACTLY the same as on my machine?
                  Get a handfull of drills, reamers etc and lightly blue them. Now check them in your machine and in any sleeves you have.
                  I think you will be suprised at the results.
                  Now which one do you follow?

                  The method I described will and does work. Others already use it. How well it works depends on the user.
                  All I ask is you try it.
                  I have a lot of admiration for the people who try things for themselves.
                  Experiance is obtained this way and not on paper. Don't get me wrong this isn't aimed at your reply. You made a valid point but experience has shown that on certain newsgroups this will then develop into a long rambling post that soon goes off topic and no one actually gets to try this method.

                  John S.

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


                  • #10

                    I think John's right.

                    No matter how you do it, you'll have to futz with it to get the blue even on both ends.

                    Tool wear, and even heat build up (in the tool) can cause deviations in this range.

                    One way I check tapers is to take a known good taper and clamp it (with electrical ties, bunjie straps, etc) on to the taper being cut, but at 180* and measure over both tapers with a mic.

                    Both readings should be the same from end to end.

                    If not right, make half the correction required with an indicator.

                    It's best to undercut the center of the taper to minimise tool wear and fitting.
                    That portion dosen't do anything anyway.



                    • #11

                      Get an new Andrychow 17"x84" with DRO for about the same...

                      (better lathe, also Polish - the shops around here love them)

                      So, you advocate the .020" below center tool height to get that parabolic shape we all pondered over in an older post?

                      [This message has been edited by Thrud (edited 11-19-2002).]