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  • cutting a taper

    I am trying to make the model cannon project in The Home Shop Machinists Handbook. I am at the point of having to cut a one degree taper on the barrel. I cannot make heads or tails of the instructions in the book or in any references that I have. I have a 9 X 19 Jet lathe. Can someone please help? Thanks

  • #2
    When I need to do this type of work, I fit a boring head in my tailstock and off set the the tailstock by half the amount I need the taper to be. Works great and is cheap. You can get a boring head fitted for your tailstock at enco of msc for about $150.00.
    Wade

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    • #3
      To elaborate a bit.....

      wade_he is assuming you'll turn the job between centers, with the tailstock center deliberately misaligned (i.e. off-center) so the workpiece is angled. That's the classic way of turning a taper. The horizontal position of your tailstock ought to be adjustable, probably via a couple of setscrews, and in the absence of any special tooling that's the way to do it. wade_he gets around the need to move the tailstock over by putting the tailstock center in a boring head and shifting that, which avoids the problem of having to re-align the tailstock center when you're done.

      Another way of doing it is to swivel your compound rest around to the angle you need and apply the cut with that. Most likely the travel distance of the compound won't be enough to cover the full length of the barrel, but by careful work you can do the cut in stages, winding the compound back, moving the carriage over, and picking up the cut where you left off. You may need to blend the transition points a bit with a file and/or emery paper, but in this case as long as it "looks right" it is right.


      ----------
      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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      • #4
        michaelj,
        I picked up this Copyrite tracer off Ebay for $150. You see them once in a while.
        You could make a battery of guns real quick.
        here are a couple of photos.

        http://www.geocities.com/kapullen2000/photopage3

        Kapullen

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        • #5
          level your lathe with a precission level to a nats a ...... then stick a quarter under one leg and you should have about the right taper.

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          • #6
            Hey trap,
            Does it matter if you got a 20 inch, or a 50 inch between center lathe?
            Do you put a fifty cent piece under the longer machine.
            Suppose the lathe has a center support?
            Which leg do you put it under?
            The center one?
            How bout if you got a monarch EE, or hardinge toolroom lathe?

            Just like to know.
            mite

            [This message has been edited by metal mite (edited 05-04-2002).]

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            • #7
              Trap: I have used lathes aboard ships (no I have not spent time in Navy) tell me why every one says "level your machines". Flat is fine enough so far as I know. Not giving any one a hard time but I really want to know. I spent some time just waiting for a tool to roll back to me, while a lath was cutting away. I am sure the decking flexed a little but i didnt see it on the work.
              Steve

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              • #8
                <font face="Verdana, Arial" size="2">Originally posted by michaelj:
                I am trying to make the model cannon project in The Home Shop Machinists Handbook. I am at the point of having to cut a one degree taper on the barrel. I cannot make heads or tails of the instructions in the book or in any references that I have. I have a 9 X 19 Jet lathe. Can someone please help? Thanks</font>
                \"TOOL SLUT\"

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                • #9
                  <font face="Verdana, Arial" size="2">Originally posted by michaelj:
                  I am trying to make the model cannon project in The Home Shop Machinists Handbook. I am at the point of having to cut a one degree taper on the barrel. I cannot make heads or tails of the instructions in the book or in any references that I have. I have a 9 X 19 Jet lathe. Can someone please help? Thanks</font>
                  \"TOOL SLUT\"

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                  • #10


                    to michaelj

                    in response to your question please contact me at 250 295 0020 i think i can answer your question and sace you a lot of time and money
                    \"TOOL SLUT\"

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                    • #11
                      The reason they tell you to level the lathe is it is an easier concept than "the lathe bed needs to be in plane". If your level is of high enough acuracy, you will have both a level lathe and one that is in plane.

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                      • #12
                        Yes -- "level" is only a means to an end. The lathe doesn't care if it's level or not, within reason. The important thing is to get the spindle and ways so they're in alignment. A precision level is one way of doing it, although personally I don't think it's all that great a way because you're not actually measuring what you care about. I prefer "Rollie's Dad's Lathe Alignment Technique," discussed at length a couple of weeks ago, because it concentrates on alignmnet (what you really care about) and doesn't worry about "level" at all.
                        ----------
                        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


                        • #13
                          Back to cutting tapers... Another technique is one adapted from Guy Lautard's method for cutting balls. Cut a bunch of equally sized steps, paint the whole surface with layout dye and file the steps off. The layout dye is to tell you where the low spots are.

                          On the assumption that the 1 degree is the angle between the surface and the centerline, the radius changes .017" (the tangent of 1 degree, rounded to .001) per inch of length. If the taper is 6" long, to pluck a number out of the air, the radius changes by .102" in 6". Round that to .100" to make things easier, and you've got 100 steps, each .060" wide and .001" deeper than the one before it. Whether to start at the maximum diameter and step in or start at the minimum diameter and step out, I'll leave up to you. Likewise whether to cut to the left or the right. If .001" x .060" sounds really boring, 20 steps at .005" x .300" probably wouldn't require all that much more filing.

                          This technique can also be used to produce machine tapers.

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                          • #14
                            A not to be overlooked advantage to having a machine level is that a good level can then be used in many instances to set up a job, fixturing, or do simple indexing, etc.
                            Jim H.

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                            • #15
                              I agree with all thats been said. But I think a person who needs advice on cutting a taper wont be able to level. More important, how to know if it even requires alignment.
                              I expressed my self poorly but I meant, if its "flat" (cuts correctly- what ever that means) then work on learning to do a taper to specs- dont blame the machine becasue its not level and you can't level it.
                              Steve

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