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  1. #1
    elanjacobs is offline Apprentice gear maker and machine doctor
    Join Date
    Aug 2008
    Location
    Melbourne
    Age
    30
    Posts
    711

    Default Hobbing baby bevel gears

    Thought I'd share this as I'm guessing most people here wouldn't have been exposed to this sort of specialised work.

    One of my recent jobs at work was cutting some small brass bevel gears (I think the pitch was Mod 0.4) on our Mikron 120.01 bevel gear cutter

    IMAG3282.jpg

    The process is essentially the same as hobbing in that the cutter and workpiece are synchronised in rotation as the work is fed across, but there are a few key differences in the cutter itself. The cutter just has 2 wings that form the teeth as opposed to a proper hob, there are also a range of cutters for each tooth pitch, much like the different numbered gear cutters for mills, which are chosen based on the size of the gear and the number of teeth to be cut. Another major difference is that each wing cuts only one flank of the gear teeth, so the cutter needs to be centralised with the aid of a microscope attachment (which I was firmly told to NOT drop at any cost , this machine is some 50 years old and spare parts don't exist)

    IMAG3301.jpgIMAG3302.jpg

    All the cutting parameters are set via a gear train, the cutter spindle is tilted over to the helix angle of the cutter and the work spindle is set to the required pitch angle of the gear (in this case, 45 degrees)

    IMAG3290.jpgIMAG3288.jpg

    There's a deburring attachment to clean up the back of the gear as it's being cut, a hard stop for the starting position and an automatic stop as well, so it's simply a case of loading each blank on the arbor (which is held in a collet and adjusted to a maximum of 0.0005" total runout) and flicking the start lever.

    IMAG3284.jpgIMAG3283.jpgIMAG3289.jpgIMAG3287.jpg

    Some time later there's a finished gear

    IMAG3285.jpgIMAG3286.jpg

  2. #2
    Join Date
    Dec 2013
    Age
    53
    Posts
    989

    Default

    Amazing little machine, thanks for sharing
    Using Tapatalk

  3. #3
    Join Date
    Nov 2008
    Location
    Perth WA
    Age
    68
    Posts
    6,284

    Default

    Wonderful photos of a beautiful little machine and the work it produces!

    Than you Elan.

    Bob.

  4. #4
    Join Date
    Sep 2006
    Location
    Mallacoota,VIC,Australia
    Age
    50
    Posts
    861

    Default

    Great job. Looks like an old machine, but she does beautiful work. Thanks for sharing.
    All The Best steran50 Stewart

    The shortest way to do many things is to do only one thing at once.

  5. #5
    Join Date
    Dec 2007
    Location
    Adelaide
    Posts
    309

    Default

    Very impressive, that's great work and I'm a bit envious - that is the machine I needed a few weeks back, I'm working on a model 4 stroke engine and needed a pair of 45deg bevel gears for the distributor drive, armed with a set of 0.4Mod involute cutters it took me 3 goes before I had just 1 gear, the second one was just a rerun so only took about 10-15 min, both gears are made from 1020 MS, the socket head screw in the pic is one of the 3mm head bolts.

    gears 2.jpg

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