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  • Gear Grinding

    I have got few gears for my lathe but these are not original and not ground.
    They are meshing correctly though but there is more noise than need be.
    I know that gears are being ground but this by descriptions available seems too cumbersome to bother with.

    I got IMO interesting idea, how such a task could possibly be done in a lazy way.

    First carefully file with diamond impregnated file grit 600 meshing surfaces to clear some obvious nuisance.
    Second make some dummy gear from aluminium which would mesh with new gears on powered jig like setup, add some gear oil and add some abrasive like silicon carbide grit 500 to make a dispersion and allow the system to run until new gear is ground & polished.

    Sort of lapping like tactic.

    After a while clean a new gear and lets hope it will mesh well and work quiet.

    Now, did anyone of you have tried it?
    Is it worth trying or just a waste of time and materials?

    Thanks for any comments.

  • #2
    I'd suspect that a ground set of spur gears would still be noisier than a decently cut set of helical gears. But change gears or QC box gears are not in a setup that accepts helical gears well, helical have end thrust.

    I wouldn't waste the time dressing up a pig. Deal with it.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      Originally posted by Martin0001
      I have got few gears for my lathe but these are not original and not ground.
      They are meshing correctly though but there is more noise than need be.
      .......

      Thanks for any comments.
      Maybe the noise is from the gears being meshed a little too tightly. My old lathe with change gears really growls if I replace the change gears and don't leave enough space between the teeth, about the thickness of a piece of paper (.003).

      Comment


      • #4
        Any straight cut gear is going to make a little noise.
        I would try running them with diamond past and lap them in so to speak. That should quiet them down a bit, how much??????? hard to say,
        I can't see where the gears in a quick change gear box turn fast enough to make any noise, it's everything else in between that does.
        My Clausing is pretty quiet when the gears are running in low range, high range, they sing a little.

        JL...............
        Last edited by JoeLee; 03-12-2012, 10:25 AM.

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        • #5
          Try a quick and cheap solution first.

          Use some 'open gear' lubricant.
          Paul Compton
          www.morini-mania.co.uk
          http://www.youtube.com/user/EVguru

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          • #6
            +1 for EVguru
            gvasale

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            • #7
              Two things or maybe three or four

              1) Are the gears too tight (try the paper trick mentioned above)

              2) Are you running them dry? If so "Way Oil" seems to work well

              3) Is the shaft to gear fit correct? A sloppy fit will make the gears sing. Another place to oil as well.

              4) Are the "new" gears the same DP and Pressure Angle?

              Comment


              • #8
                Originally posted by nctox
                Maybe the noise is from the gears being meshed a little too tightly. My old lathe with change gears really growls if I replace the change gears and don't leave enough space between the teeth, about the thickness of a piece of paper (.003).
                I'll second that. My old Logan will create a symphony of varying noises if the stud, idler, QC gear train is too tight. I'd say loosen 'em up a bit to see if you change anything.
                Wayne

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                • #9
                  My gears are certainly not meshing too tightly.
                  I do not run paper test each time (too tedious) but I always look for minute backlash to exist.
                  Peculiarity of ML7 is that on odd occasion a spec of swarf may drop from the spindle into quadrant (I know, that can be dealt by "journal extension pipe", but sometimes this is forgotten or swarf will drop upon removal of said pipe).
                  So I do allow a bit more clearance, just to prevent gear damage (and bottoming can also easy do that).

                  And still, old gears are hardly heard and new are making much clattering noise.

                  I know, noise itself is nothing critical, as long as it is not an indication of damage, but it is certainly something best to live without.

                  Comment


                  • #10
                    There's an old and very worn ML7 in the corner here at work.

                    Most of the change gear stack has never been used and peeling off the packing grease from a couple reveals machining marks running along the length of the teeth, so I'd say they were hobbed. Those that have been used have a fairly even polished looking face to the teeth, but the machining marks are still visible in places.

                    The popularity of the Myford and the high cost of some parts means there are a lot of poor patern parts out there. Even if the tooth profile of your new gears is correct it wouldn't be unusual for a new gear to be noisy when run with an old gear.

                    The open gear libricant really does work. The gears on my Harrison L5 are hardened steel and can 'ring' or even howl at times unless damped.
                    Paul Compton
                    www.morini-mania.co.uk
                    http://www.youtube.com/user/EVguru

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                    • #11
                      also, with involute gears a little extra clearance is far better than too tight.
                      gvasale

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                      • #12
                        "Grinding/lapping" gears while running them is pretty well a waste of time as the gears will squeeze the grit out - just like putting the and of a tube of tooth paste between two rollers.

                        Involute gears do not move relative to each other as they stay in contact by rolling along the line of action:



                        To grind or lap a gear set it must be simultaneously rotated and at least one gear oscillated axially/"up and down".

                        Grinding this way will not do much to correct badly worn gears especially as gear trains are relatively lightly loaded at moderate loads.

                        But as others have said - leave it alone and make do with it as the worn gears wil be noisy but will run well enough for a while yet.

                        ie "If it ain't busted - don't fix it".

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                        • #13
                          Since no gear can ever be a 'perfect' involute, especially inexpensively made change gears, it seems possible that lapping the gears together might improve the form by removing the parts which are sliding rather than purely rolling. I agree that noise just goes along with spur gears. Sheldon used a fibre gear in their gear train at one time. My Sheldon has a bronze gear and the gear train is very noisy at higher speeds; there is also some very noticeable gear wear.

                          I suspect some well placed damping and insulating material would reduce the gear noise noticeably.
                          Don Young

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                          • #14
                            Gears will "rub" on a good involute if the centre distances are incorrect (too wide or too narrow) but the wear is very small but accumulates over time in use to be a nuisance. Poor gears will only make good gears worse.

                            Some gears are worn more on one side that the other - look for the better sides and keep them in mesh.

                            The "cigarette paper" clearance test is not universally correct - even on good or new gears - and on very few others.

                            I suggest that some read Machinery's Hand Book 27 pages 2067 to 2073 for "Backlash in Gears". It might open the eyes of some who will insist on using "Rules of Thumb" as the "be all and end all" of things that need to be correct.

                            Even if the cigarette paper (or any valid) test was correct for new or good gears that using the test to close up excessive wear only closes the centre distance between the gears which causes more wear due to rubbing on the involutes due to the pitch circles over-lapping and on and on it goes.

                            With worn gears I'd be more inclined to set the gears to their original centre distance and let any wear or "rattling" look after itself.

                            Involute meshing is only correct when the pitch circles are tangent (just touching) to each other.

                            If they are too close they are over-lapping and will "rub" as well as "roll".

                            Similar conditions apply if the pitch circles too far apart.

                            Using the "cigarette paper" and similar invalid tests on any/most gears and particularly on worn gears makes the pitch circles over-lap resulting in more wear and noisy running. The environment that a lathe gear train operates in is abrasive as congealed oil or grease with grit etc. is a pretty good grinding compound.

                            If my gears (gear train) were showing that much wear I'd perhaps replace them but I'd check out my other gears first - head-stock, quick-change gear-box, apron/carriage etc. as well.

                            Last edited by oldtiffie; 03-13-2012, 01:38 AM.

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                            • #15
                              Lapping and superfinishing is used in hypoid gear production (i.e. crown and pinion gears for axles). The general aim is to reduce noise since this is unacceptable in a modern car. The actual effect is to reduce transmission error (loss of conjugate action) and this makes sense, since it is a potent source of noise. However, lapping of this kind may not actually improve the finish of the gears, particularly the ring gear which can actually deteriorate with lapping. Therefore the process needs to be closely controlled. In order to get this level of control a lot of research and development is needed, and that is the problem with home workshop based gear lapping where there is no real possibility of measuring the effect of lapping in such areas as gear tooth profile etc.

                              I would leave the gears alone and just concentrate on setting them up right and using an appropriate lubricant.
                              Bill

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