Boring a partially tapered hole?

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  • Spookydad
    Senior Member
    • Dec 2011
    • 200

    Boring a partially tapered hole?

    Can anyone tell me the best way to bore a tapered hole if the taper starts part way down?

    In this case the material is oak or maple, inside a steel sleeve. I am thinking that installing the sleeve first may be the way to go.

    This drawing has the dimensions in mm.

  • TGTool
    Senior Member
    • Aug 2005
    • 3613

    #2
    I think a form tool is your best, or maybe only shot. You can drill the large diameter or slightly under down to where the taper starts, then drill to depth at the small end diameter and finish with the form tool. I've bought spade drills for wood just to modify for particular shapes I needed. You can grind and file them since they're not hard. You'll want at least a jury rigged V-block to check both edges as you work on them to maintain reasonable symmetry.
    .
    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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    • Toolguy
      Senior Member
      • Jan 2010
      • 6666

      #3
      Tapered Hole

      I would use a small diam. boring bar. Drill a hole a little under 9mm. Set the compound to cut the taper. Bore the straight part using the carriage as normal and stop at the depth where the taper starts. Then wind the compound slide to the bottom of the hole and you're done! You will have a perfect transition from the straight to the taper. Do rough and finish cuts, not all at once.
      Kansas City area

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      • Don Young
        Senior Member
        • Jun 2004
        • 1163

        #4
        I believe that taper could technically be bored on a lathe by doing the straight and taper sections separately with a taper attachment or compound rest. It would require some careful measuring and would require an extremely long and small diameter boring bar. I think a form shaped reamer/drill could be made much easier. Removing most of the wood by step drilling would make it easier to finish the taper, regardless of the method used.

        Edit: Toolguy's idea sounds best for boring.
        Last edited by Don Young; 02-17-2012, 09:59 PM.
        Don Young

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        • RussZHC
          Senior Member
          • Mar 2010
          • 2411

          #5
          Not sure, but a shot...

          Cross your fingers and hope there is a taper drill that you could tweak to fit?

          Most of the taper drills for wood I could find referenced screw sizes but if you could find one large enough so that the max diameter at the largest part of the taper matched the straight section above and just bore down? The issue would appear to be those taper drills would be longer than necessary at that taper than you need for the bore bottom so that would have to be ground away.

          Edit: looked at the diagram again, the basic idea should work but you would have to bore the top straight wall sided area to correct diameter after the taper was done
          Last edited by RussZHC; 02-17-2012, 09:59 PM.

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          • beckley23
            Senior Member
            • Sep 2003
            • 806

            #6
            I don't see a dimension for where the taper starts.
            Harry

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            • Stepside
              Senior Member
              • Mar 2002
              • 1785

              #7
              I printed the drawing

              There is a dimension missing or I just don"t understand. How far down the bore is the 14.5 diameter? I also think it says the straight bore is 6mm deep and 16.8 diameter. It then tapers to 14.5mm and from the 14.5 it tapers to 9mm. All in all a confusing drawing with missing numbers. Does the drawing of the mating part have the needed information?

              If one had the dimensions, then turn the shape out of bar stock (something that will take and hold an edge. Remove one side down to the midline for the 70mm length. Remove the opposite side until your bit is about the thickness of a spade bit. File the needed relief on both cutting edges being careful to preserve the shape.

              Pilot drill and maybe even step drill so you are using your bit as a tapered reamer. I would install the steel/metal sleeve before doing any of the drilling.

              Let us know how you end up doing the job.

              Comment

              • Spookydad
                Senior Member
                • Dec 2011
                • 200

                #8
                This is the other half of the drawing and a picture of the wooden poles. They aren't an "exact" fit. In practice they can be quite wobbly when put together.



                Comment

                • justanengineer
                  Senior Member
                  • Nov 2010
                  • 2220

                  #9
                  Originally posted by Toolguy
                  I would use a small diam. boring bar. Drill a hole a little under 9mm. Set the compound to cut the taper. Bore the straight part using the carriage as normal and stop at the depth where the taper starts. Then wind the compound slide to the bottom of the hole and you're done! You will have a perfect transition from the straight to the taper. Do rough and finish cuts, not all at once.
                  x2. Use a carriage mic stop to get a uniform depth on the straight portion, then simply use the compound to cut the taper.
                  "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

                  Comment

                  • baldysm
                    Senior Member
                    • Oct 2010
                    • 106

                    #10
                    Looks to me that the 2 pieces aren't designed to go together. The male shaft is straight on the end, and then starts a taper. The female shaft is straight and then tapers at the bottom of the hole.

                    The male shaft is 13.5 mm diameter on the straight part, and the female taper is 14.5mm in diameter necking down to 9mm. So the male wont even come close to the bottom. Yup, the end of 1 will fit into the other, but it's gonna wobble.

                    I don't know what these poles are or what they do. I would be tempted to just bore a straight hole in the female end so the straight diameter just slides in, and use the taper on the male to jam/lock the shafts together.

                    Comment

                    • Spookydad
                      Senior Member
                      • Dec 2011
                      • 200

                      #11
                      I did a CAD drawing last night and it would appear that a straight taper would work just fine.

                      These are the sections of a tent pole. One was issued with each triangle and when the 4 are put together, the tent is pyramid shaped and the 4 poles hold up the middle of the tent.

                      As specified the poles were quite wobbly. After field usage, the wooden point wears down into a short taper. This seats the poles sections together and they can be quite difficult to get apart.

                      I drew the two ends with an assumed field taper and as specified.

                      Comment

                      • Spookydad
                        Senior Member
                        • Dec 2011
                        • 200

                        #12
                        This is the results. I drilled out the 9mm to full depth and then 14mm to halfway. Since the fit is sloppy and the difference in angle is so slight, I set the compound at 3.2 degrees and bored the taper. I miscalculated slightly and the opening at the end is closer to 18mm than 16.8 mm

                        The taper on the wood section goes about 1/2 way up. I set the tailstock over a few mm to achieve the taper. The copper on the end is standard 3/4" water line and is almost perfect for size.





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