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  • BETTER than Eureka!

    Maybe some of you remember a thread from a few years ago about an apparatus I built for making gear cutters using Ivan Law's "button" method.

    I saw a Eureka "form relieving tool" design in his book and it seemed to me to be overly complicated. Also, it depends on a spring to return the cutter.

    This is what I designed as an alternative. https://bbs.homeshopmachinist.net/fo...rd-alternative

    My version relies upon a crankshaft. Perhaps this would interest Brian.

    My design has several distinct advantages: it is simpler, it doesn't rely on springs, AND it can move along the carriage.

    If you think about this, it could be used to make hobs which would be helical (I think).

    I have seen a video of someone making hobs with the Eureka. It was a complicated process and demanded and the user hand hold the Eureka.

    This seemed complicated and even dangerous.

    Why then haven't I have any gear cutters? I haven't needed them.

    My interest in this, just as it has been in the freewheel hobbing, is not to make gears, but TO PROVE THE CONCEPT!

    My purpose is show that something can be done, not to make gears.

    In the next post I will say why.
    You may only view thumbnails in this gallery. This gallery has 3 photos.
    Last edited by davidwdyer; 10-18-2021, 08:36 AM.
    Vitَria, Brazil

  • #2
    Why have I not made gears or gear cutters. I don't need them at the moment!

    BUT, even more that that, someone else has found an even better method.

    This guy's idea seems even simpler. http://www.deansphotographica.com/ma...ultipoint.html

    AND I suspect this method could be used for making hobs also, using an elongated, carefully prepared, blank supported on the other end by the tailstock.

    There seems to be no need for only having four cutting "fingers" as seen in this video.

    You could do eight or more I believe using his method.

    BUT, there is an even simpler and easier way which I will reveal in the next post.
    Last edited by davidwdyer; 10-18-2021, 08:37 AM.
    Vitَria, Brazil

    Comment


    • #3
      Now here's the another important reason I haven't pursued this much further.

      Just as example: https://www.amazon.com/DP16-PA20-Gea...4556207&sr=8-2

      For 88 bucks (and some of them are even less) how can anyone justify hours in the shop messing with this.

      (By the way, sets of gear cutters are also in this price range).

      If, for some reason, the Chinese alternatives suddenly became unavailable, and we HAD to make our own, this could be done.

      But for now......

      This then led me to experiment with freewheel hobbing. I haven't worked enough on this process to produce a "perfect" gear for the same reasons that

      I haven't done it with the other methods. I don't need any. I just did enough to prove to myself that it could work. I don't have the time

      or need to go further. Perhaps I haven't convinced you, but I don't need to.

      I also see no need to dump upon dear, departed Robin.

      He may be outspoken, somewhat like a recent president, but he is willing to experiment and think outside the box.

      I greatly respect all you machinists who can take a set of plans and make a great part from them. I'm not sure I could do that anywhere as well as you.

      But innovation has a place in this field. Simply repeating what someone else has done is valuable, but not all there is.
      Vitَria, Brazil

      Comment


      • #4
        Unfortunately I can't see any of the images in your 2011 thread.

        I don't believe there is anyone here, or even on PM, who is against innovation or trying new things.

        When a hob is cutting a spur gear (depending on the pitch of the gear and its diameter) typically only one of the hob's teeth is actually cutting at any given time, with the trailing hob tooth entering its cut and the forward one leaving its cut. I believe the fatal flaw in freewheel hobbing is that, at the moment when a hob tooth bites into the gear blank, the blank is unsupported and is free to rotate. Of course this is critical to the method; it is the "freewheel" part of the technique. However, this results in an unwanted relative rotation of the blank and hob, preventing the hob from cutting the blank at the precise location it must in order to produce a proper involute gear tooth.

        You can see the result of this unwanted relative rotation on the blank in your video, in both the initial cuts on the blank and in your finished gears. The shape of the finished gear teeth is critical to properly transmitting motion and torque, and unfortunately I don't believe the ones that you have produced by your method would do either, nor survive long in any application. The teeth on your gears are clearly not involutes, as you acknowledge, and at best they can be called tooth-like. To my eye, they would mostly scrape their tips along the mating gear's teeth, producing excessive friction and wear. Yes, they seem to mesh and rotate when pushed together and moved by hand, but that isn't how they will function in any geared application.

        The focus of exploring this method has to be on producing the proper tooth form, not merely producing tooth-like projections on a gear blank. Unless and until this method can produce an involute gear tooth, there is still work to do. There isn't any reason to produce gear teeth that aren't even close to the proper shape, especially if that method requires the use of an expensive involute hob.

        Can I suggest an experiment? Take two of your freewheel-hobbed gears, plastic or aluminum, assemble them properly at their calculated center distances so that their pitch circles roll on each other, and drive them with an electric motor for an hour or two, with or without some nominal load. Repeat this experiment with a couple of purchased involute gears of the same pitch and size. Make sure to take and post detailed photos of the gear teeth before and after this experiment. This should begin to clear up whether the gears produced by this method, at the current state of its development, will be useful in application.
        Last edited by DrMike; 10-18-2021, 10:20 AM.
        SE MI, USA

        Comment


        • #5
          David D: The pics you show, are unfortunately too small to see any details.

          The general idea is reasonably clear, and what you have is definitely a proper relieving tool.

          Originally posted by DrMike View Post
          ...........

          When a hob is cutting a spur gear (depending on the pitch of the gear and its diameter) typically only one of the hob's teeth is actually cutting at any given time, with the trailing hob tooth entering its cut and the forward one leaving its cut. I believe the fatal flaw in freewheel hobbing is that, at the moment when a hob tooth bites into the gear blank, the blank is unsupported and is free to rotate. Of course this is critical to the method; it is the "freewheel" part of the technique. However, this results in an unwanted relative rotation of the blank and hob, preventing the hob from cutting the blank at the precise location it must in order to produce a proper involute gear tooth.

          .............................
          That, of course. I think several folks mentioned it in the "robint" (sp?) thread of a week or so back. The amount of trouble that causes will depend on the blank diameter, and how many times the hob has been sharpened (which increases the space between teeth).

          There is another issue.

          The helix of the hob ALSO does not guide the blank accurately. The free-hobbing concept depends on the hob driving the blank with the hob acting as a worm. It may have little friction, but there are cutting forces, and so forth.

          The problem there is the relief on the hob. The relief has the effect of increasing the effective center-to-center distance of the hob (acting as a worm). That is essentially increasing the backlash between them, so that the "guiding", or even the "driving" of the blank is not consistent and correct.

          Ideally, from the standpoint of driving the blank, you would actually want a hob that has ZERO relief. That way it would always be in contact with the flanks of the teeth it is cutting, and would drive the blank, and hold it against cutting forces, as well as is possible.

          There are some issues with lack of relief, of course. But that would be required to keep the blank more-or-less in the proper position at all times.

          I think it is a basic, built-in problem with the entire free-hobbing technique.
          Last edited by J Tiers; 10-18-2021, 11:39 AM.
          2730

          Keep eye on ball.
          Hashim Khan

          Everything not impossible is compulsory

          Comment


          • #6
            I won't go into Free Hobbing, but did want to comment on gear cutter form relief.
            The Eureka and offset turning methods require a lot of work in tooling and tool making
            Having cut a lot of gears and used this method makes it a very simple form of relief for the cutter teeth.
            I posted it some years ago and can't find the link, so I will do it again
            This method works if you made your button cutter with 8 degree or so relief on it;s cutting edge ( which should be normal )
            Now all this is by "Hand" power, not Lathe spindle turning !
            and you can see 3 pictures of the process here which is a derivation of another type of lathe work I developed called Hand ( or manual) Shaping

            Setup: ( no special tools !)
            Mount your cutter in the lathe Spindle with arbor or chuck. The cutter must not turn in it's holder as there is much torque force here !
            A drag brake on the spindle helps but is not necessary--I use the lathe in back gear as I do not want a free wheeling spindle that can cause a loss of rotary position
            Put your button tool ( that cut that blank ) in your tool post and lock it (!) and then engage it with the gear cutter tooth --just for alignment- put a carriage stop on the left side to maintain THAT location, or zero out your DRO.
            Temporarily mount a mag base indicator and ZERO the dial on top of the Button tool and then move the carriage and remove the Button tool and stick in a 3/8" or 1/2" tool blank and move it under the Indicator. You want that tool blank to be .001 to .002" LOWER than the button tool - You are now set ~

            Operation
            Bring in the blank tool and rotate the spindle bringing the gear cutter tooth into firm contact AND THEN HOLDING the spindle from moving !!
            Back the carriage away, remove the blank tool and mount the Button tool . clamp it and then return the carriage to the stop.
            Feed the button tool into the gear cutter- It will stop when it hits the cutter as it is .002" above C/L --Good .
            Now with the chuck wrench in your left hand and the right on the cross-feed handle , tighten as much as you can on the cross-feed ( heavy Force !) , pull the chuck handle to you.
            You will get two nice tapered curled chips, relieving the tooth by using the 8 degree relief on your Button tool form as a guide- works slick ..
            Repeat for the next gear cutter tooth. When done with this process, go back and relieve the center "leg" on the cutter as we only did the involute form with the two buttons.
            For that , a straight tool bit will work
            Rich


            You may only view thumbnails in this gallery. This gallery has 5 photos.
            Green Bay, WI

            Comment


            • #7
              Originally posted by Rich Carlstedt View Post
              I won't go into Free Hobbing, but did want to comment on gear cutter form relief.
              The Eureka and offset turning methods require a lot of work in tooling and tool making
              Having cut a lot of gears and used this method makes it a very simple form of relief for the cutter teeth.
              I posted it some years ago and can't find the link, so I will do it again
              This method works if you made your button cutter with 8 degree or so relief on it;s cutting edge ( which should be normal )
              Now all this is by "Hand" power, not Lathe spindle turning !
              and you can see 3 pictures of the process here which is a derivation of another type of lathe work I developed called Hand ( or manual) Shaping

              Setup: ( no special tools !)
              Mount your cutter in the lathe Spindle with arbor or chuck. The cutter must not turn in it's holder as there is much torque force here !
              A drag brake on the spindle helps but is not necessary--I use the lathe in back gear as I do not want a free wheeling spindle that can cause a loss of rotary position
              Put your button tool ( that cut that blank ) in your tool post and lock it (!) and then engage it with the gear cutter tooth --just for alignment- put a carriage stop on the left side to maintain THAT location, or zero out your DRO.
              Temporarily mount a mag base indicator and ZERO the dial on top of the Button tool and then move the carriage and remove the Button tool and stick in a 3/8" or 1/2" tool blank and move it under the Indicator. You want that tool blank to be .001 to .002" LOWER than the button tool - You are now set ~

              Operation
              Bring in the blank tool and rotate the spindle bringing the gear cutter tooth into firm contact AND THEN HOLDING the spindle from moving !!
              Back the carriage away, remove the blank tool and mount the Button tool . clamp it and then return the carriage to the stop.
              Feed the button tool into the gear cutter- It will stop when it hits the cutter as it is .002" above C/L --Good .
              Now with the chuck wrench in your left hand and the right on the cross-feed handle , tighten as much as you can on the cross-feed ( heavy Force !) , pull the chuck handle to you.
              You will get two nice tapered curled chips, relieving the tooth by using the 8 degree relief on your Button tool form as a guide- works slick ..
              Repeat for the next gear cutter tooth. When done with this process, go back and relieve the center "leg" on the cutter as we only did the involute form with the two buttons.
              For that , a straight tool bit will work
              Rich

              Great idea. And it seems that it works! It seems you are saying you get the relief you need by starting your cut slightly under center. Is that correct?
              Vitَria, Brazil

              Comment


              • #8
                Seems like "pressure tapering".... the heavy pressure gets the tool cutting, and it cuts deeper as the cut progresses, making the taper.

                If the same material, and the same pressure each time, it should be repeatable. Only works for short cuts, since you only get as deep a cut as you dialed-in when applying the pressure.
                2730

                Keep eye on ball.
                Hashim Khan

                Everything not impossible is compulsory

                Comment


                • #9
                  Originally posted by davidwdyer View Post
                  Great idea. And it seems that it works! It seems you are saying you get the relief you need by starting your cut slightly under center. Is that correct?
                  Correct ! Its the heavy pressure that starts the cut and you maintain the pressure through the cut and you can feel the cross-slide handle moving clockwise as you rotate the chuck..
                  it's important to have that 8 Degree +/- forward relief on your button tool.
                  After this process, you can heat treat the cutter, and then stone the front cutting face with a India /Arkansas stone
                  Rich

                  Look closely at the two pictures of the button cutters. The shank has been milled at 8 degrees, and then I come back and surface grind the tops flat.
                  In picture # 1 , I milled half of the button so I had less to grind . If you do the shank right, you can use a belt sander instead of a surface grinder .
                  You can see it being ground in this picture , cutter buttons down
                  Last edited by Rich Carlstedt; 10-19-2021, 02:02 AM.
                  Green Bay, WI

                  Comment


                  • #10
                    Forgot the pic
                    The Brass sheet allows you to grind only the button until it is flat /parallel to the shank plane
                    then if the button is fully ground, it is finished. If not , remove the brass and continue
                    Rich
                    You may only view thumbnails in this gallery. This gallery has 1 photos.
                    Green Bay, WI

                    Comment


                    • #11
                      I find it interesting that in a discussion about all the inaccuracies of the various methods of making these cutters, no one says a single word about the use of round buttons to form a tool for cutting an involute curve.
                      Paul A.
                      SE Texas

                      And if you look REAL close at an analog signal,
                      You will find that it has discrete steps.

                      Comment


                      • #12
                        Originally posted by Paul Alciatore View Post
                        I find it interesting that in a discussion about all the inaccuracies of the various methods of making these cutters, no one says a single word about the use of round buttons to form a tool for cutting an involute curve.
                        That's because the button method comes from an "authorized" source: Ivan Law. I've wondered about (and I think others have commented upon, and I think that

                        is what Rich is doing with his angled shank) is that a tilted round more closely approximates an involute shape.
                        Last edited by davidwdyer; 10-19-2021, 09:02 AM.
                        Vitَria, Brazil

                        Comment


                        • #13
                          I have also wondered about why no one commented on this video: http://www.deansphotographica.com/ma...ultipoint.html

                          It seems to me that this guy found a really good way to do things. He's obviously limited to using a four jaw chuck as his indexer and so only gets four teeth.

                          But anyone with a digital readout could make a bolt hole circle pattern and make as many teeth as he likes quickly and easily.

                          This method can be done with machine power and gives the relief angle needed.
                          Vitَria, Brazil

                          Comment


                          • #14
                            Originally posted by Paul Alciatore View Post
                            I find it interesting that in a discussion about all the inaccuracies of the various methods of making these cutters, no one says a single word about the use of round buttons to form a tool for cutting an involute curve.
                            It seems like this thread is more about (has devolved into?) making and relieving the teeth of milling cutters. The techniques described here could apply to most any home-shop milling cutter. The fact that the specific cutters used as examples only approximate an involute curve doesn't really seem like the point, even though it is true.

                            Originally posted by davidwdyer View Post
                            That's because the button method comes from an "authorized" source: Ivan Law. I've wondered about (and I think others have commented upon, and I think that is what Rich is doing with his angled shank) is that a tilted round more closely approximates an involute shape.
                            Can you prove that a tilted circle (an ellipse) is a better approximation to an involute than a circle, or even that his method of tilting gives a more accurate result? Is it worth the effort knowing that he is making a single-space cutter, and unless he will make one for each gear he cuts, he will be approximating a whole range of tooth numbers with each approximate round-button gear cutter he makes?

                            Originally posted by davidwdyer View Post
                            I have also wondered about why no one commented on this video: http://www.deansphotographica.com/ma...ultipoint.html
                            It seems to me that this guy found a really good way to do things. He's obviously limited to using a four jaw chuck as his indexer and so only gets four teeth.
                            He eventually got it done, but there are far more straightforward ways to make a multi-tooth milling cutter.
                            Last edited by DrMike; 10-19-2021, 09:31 AM.
                            SE MI, USA

                            Comment


                            • #15
                              He eventually got it done, but there are far more straightforward ways to make a multi-tooth milling cutter.[/QUOTE]

                              I am very interested in knowing about such techniques. As you can see from this thread, making gear cutters

                              has always interested me but I've never seen an easier way. I'm all eyes and ears.
                              Vitَria, Brazil

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