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Eureka style gear hob reliever video

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  • Eureka style gear hob reliever video

    For several years I have been trying to make my own gear cutting
    hobs and relieve their cutting edges.

    I started with the Eureka relieving
    attachment found in Ivan Law's Gears and Gear cutting Workshop
    Practice Series 17 which is intended to relieve form cutters.

    I followed the plans closely because I had no idea how it worked
    except for making it longer to hold a hob to be relieved.

    The lead of a diametral pitch hob is a factor of pi so I used a pair of
    gears, 42t and 44t, keyed together to get 22/7 pi into the lead.

    Like metric conversion gears ,this means the half nuts must stay
    engaged and the lathe reversed for each pass. This works fine
    for plain turning but is a problem with the reliever since it drives
    through a ratchet and loses place when reversed. I was able to
    relieve hobs but it was very tedious since the tool had to be
    reset to pick up the thread.

    My solution is to make the Eureka long enough to hold the hob
    and a pattern screw to match the hob. A half nut follows the
    pattern screw and drives the lathe carriage.

    Each gear pitch needs its own nut and pattern screw but it
    always engages correctly.

    My reliever and plain arbor are 7/8" diameter with a 1/8" keyway.

    The hob is put on the reliever and marked with a tool to show
    where the gashes need to be.

    Here is a video of a device I made to relieve gear cutting hobs.
    It is a modified Eureka relieving attachment.

    http://tinyurl.com/6qyxoh

    This is the book where I got my plans for the Eureka relieving
    device. It is shown on pages 123 thru 130. I bought the book.

    http://tinyurl.com/5ey4xz

    This is Balzer's geared reliever but it is not the one he manufactured.
    It uses a trick gear which I think would work since the odd part
    does not run under heavy load.

    http://preview.tinyurl.com/5jvngc

    This is Balzer's reliever which he manufactured. The Eureka was
    reverse engineered from a picture of this. See pages 26 thru 28.

    http://tinyurl.com/5cfjup

    This is Taylor's paraphrase of Balzer's reliever

    http://preview.tinyurl.com/6e6pym


    Best regards, Charlie

  • #2
    awesome

    something is confusing me though (it's not too hard to do)

    does the hob and lead screw for the cutter pivot on the tailstock??

    Comment


    • #3
      Yes ,
      The whole reliever runs on the regular
      lathe centers. The shaft inside the arbor
      with the hob and screw has its centers
      offset .030" to give .060" relief on each
      tooth that is cut. This is from the Eureka
      design.

      Comment


      • #4
        Charles,
        Very impressive and a good adaption of logical thought.
        I am very impressed .

        .
        .

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



        Comment


        • #5
          Brilliant. Very clever.

          Peter

          Comment


          • #6
            I always wondered how a relieving attachment worked ,thankyou.

            Comment


            • #7
              ______superb!

              Comment


              • #8
                Very nice,how adaptable is it to other work like milling cutters?

                I am working on copying Hendy's design which is an eccentric driven tool post that is timed to the spindle via a change gear set.

                http://www.lathes.co.uk/hendey/page11.html
                I just need one more tool,just one!

                Comment


                • #9
                  Originally posted by quasi
                  I always wondered how a relieving attachment worked ,thankyou.
                  Actually, the traditional style is geared from the headstock and reciprocates the crosslide.

                  The video one is nicer, less hassle.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Great job Charlie -- I have no idea how you managed to track down the original Balzer patent (from 1894!), since Ivan Law and George Thomas couldn't find it (according to Ivan's book).

                    I just printed out both patents, but from glancing at the drawings, it looks like the Eureka is more like Taylor's version than the one described in Balzer's patent.

                    I really like the half nut you added to advance the reliever -- very clever!
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                    Comment


                    • #11
                      Thank you Charles Lessig

                      Thank you, thank you, thank you Charles Lessig (OP).

                      Magnificent - in every respect. A very elegant solution indeed.

                      I have just ordered the book - plus another on Tool & Cutter grinding - from Amazon.com

                      This forum is fabulous the way the people on it turn up such great material.

                      I've been waiting/thinking about this for years.

                      The one I used in my younger days (50+ years ago) was hydraulic - and was controlled by a follower/stylus following a cam.

                      One of the main problems with these "home made" hobbing cutters is that all too often or mostly the profile is set at zero top rake - ie with no "hook angle" (as on wood saws and router cutters) and are inclined to "thump". The "throat"/groove ahead of the cutting face is also not spiral-cut to the normal of the hob helix angle and so one side of the profile face will have an effective positive side rake and the other an equal negative side rake (same as a screwing tool that is cut/set "flat" on a lathe).

                      But as for the lathe tool - keep it slow and sharp with plenty of cutting oil.

                      Care must be taken when grinding/sharpening the cutter as the profile of the "face" of the cutting teeth must be maintained - ie the same "hook" or "back-rake" must be maintained.

                      A hobbing cutter - as this is - will quire often "drive" the "blank"/job which can "free-wheel" without physical or electronic (CNC) connection between the cutter and the work - particularly - where a helix or "worm/wheel" situation arrives. A spur gear is only a spiral gear with an infinitely long helical pitch and infinitely small helix angle after all.

                      Comment


                      • #12
                        Originally posted by wierdscience
                        Very nice,how adaptable is it to other work like milling cutters?

                        I am working on copying Hendy's design which is an eccentric driven tool post that is timed to the spindle via a change gear set.

                        http://www.lathes.co.uk/hendey/page11.html
                        For other work like milling cutters you just lock the carriage and don't use the feed screw that Charles has fitted.

                        The Hendy one is set for what number teeth via the change hears but for a hob still has the problem that Charles came across in that the travel via the leadscrew has to have the pi ratio in it and you can't disconnect the leadscrew after each cut.

                        .
                        .

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



                        Comment


                        • #13
                          Thank you all for your encouragement and interest.

                          If I make another reliever I would follow Balzer's 1896
                          design with its adjustable eccentric. It is a little more
                          complicated but more straight-forward to make.

                          I think the pattern screw should be longer than the
                          hob and not the same. My reliever has a broad
                          canvas-phenolic nut that starts and ends half engaged.
                          The pattern screw is aluminum.

                          A cast iron, locking, double half nut on a steel screw might
                          work better. The time to stop is when it gets more
                          elaborate than a backing-off lathe.

                          The nut mechanism mounts on my follower rest holes
                          and is steadied by a cone screw in a center-drilled hole
                          on the opposite side of the saddle. This is on a 9" South
                          Bend lathe.

                          The pivots are all cone-pointed set screws into center
                          drilled holes. There is very little lost motion.

                          First I get as much metal removed by plain turning and
                          milling as I can and I then do the relieving.

                          The gashes should be as small as practical at first since
                          the start of the teeth is imperfect as slack is taken up
                          at the beginning of each cut. Later the bad parts can
                          be milled off, making the gashes wider.

                          The tops of the teeth are relieved first with a flat
                          cutter then the sides are done with an acme shaped
                          cutter. It helps to blue the hob so you can see
                          what you are doing better.

                          It is very satisfying to find other people interested
                          in this sort of thing.

                          Charlie

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                          • #14
                            Thats trick, its fun just to watch it work.

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                            • #15
                              By the way guys, don't forget that John built the Eureka reliever in Ivan Law's book several years ago, and posted the video here.

                              I can't find the video on John's page, so I just uploaded it to RapidShare:

                              http://rapidshare.com/files/132919594/MOV01374.MPG.html

                              John: let me know if you want me to take it down...
                              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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