Watch and clock sized gear hobber

Discussion in 'Horological Tools' started by motormaker, Jul 15, 2012.

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  1. motormaker

    motormaker Registered User

    Apr 5, 2010
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    Tucson, AZ
  2. Watchfixer

    Watchfixer Registered User

    Jun 11, 2011
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    TV repair tech.
    Actually this is powered rounding up machine and cutter wheels looks like serrated wheel with a one slit and slot pushed to one side to advance wheel one tooth on cutter's one turn. Requires precut gears to close size even with square teeth. The true gear cutter is flying cutter and indexing wheel or CNC with flying cutter.

    A hobbing machine turns the cutting gear and blank together while cutting gear plunge up and down with each cut and rotating very slowly. Produces wrong type of tooth shape for clock or watches.

    Cheers, Watchfixer
     
  3. Kevin W.

    Kevin W. Registered User

    Apr 11, 2002
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    I work at the Veritas Tools machine shop.
    Nepean, Ontario, Canada
    Wouldn,t you just change the cutter to the tooth shape you need.If you google hobber it shows various machining done by these machines.I would like to see this old one in operation.
     
  4. motormaker

    motormaker Registered User

    Apr 5, 2010
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    Tucson, AZ
    #4 motormaker, Jul 15, 2012
    Last edited: Jul 15, 2012
    No, my new toy is a real hobber. As I indicated on the web page, the cutter and wheel being cut are geared to turn together. The hob will be screw shaped (with cutting teeth) and having the appropriate tooth profile. As long as the same tooth size is used, everything should revolve and cut perfectly without needing to change the drive gears for different diameter wheels. It is NOT a rounding up tool.
    Jim
     
  5. Watchfixer

    Watchfixer Registered User

    Jun 11, 2011
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    Very cool. :) how one make an screw-type gear hob cutter. I'm sure one could make the machine clone and make high quality gears from that so others do that as well?

    Cheers, Watchfixer
     
  6. motormaker

    motormaker Registered User

    Apr 5, 2010
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    Tucson, AZ
    Tool steel turned on a screw cutting lathe using a tool bit precision ground to the "tooth gap" shape. The resulting screw shape gets drilled/reamed to fit the hobber, teeth ground in to create a cutting edge with relief, hardened, and annealed. That is how I will make the hob to match the gear that is on the machine. Machining will be on my 11" Sheldon lathe. Grinding on my Boyar-Schultz surface grinder or my Gorton 375 tool and cutter grinder.
    Jim
     
  7. Watchfixer

    Watchfixer Registered User

    Jun 11, 2011
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    Okay, is the hobber screw cutter's profile is exact match to the cut gear provided that gear is cut (milled by the hobber)?

    Cheers, Watchfixer
     
  8. motormaker

    motormaker Registered User

    Apr 5, 2010
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    Tucson, AZ
    Please restate the question.
    Jim
     
  9. StephanG

    StephanG Registered User

    Jun 24, 2007
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    Australia
    My understanding of the hobbing process is that the cutter takes the place of a second gear in a pair.
    If you think about 2 gears that match as long as you use the same DP then the number of teeth does not matter and the 2 should still mesh.
    If you look at the teeth of 2 different gears (say a 30 and a 60 tooth) in isolation they are different and to cut them one at a time requires a library of cutters
    but when the blank and the cutter are both rotating the movement of the parts and the way they interact with each other generates the profile needed.

    If you looked at the profile of a tooth on a hobbing cutter I suspect it would be different again from a single tooth cutter as it requires the movement of the blank over it to generate the correct shape.

    I am not sure when hobbing machines became popular but I have often wondered why they were not more used in making watches.
    Perhaps the complexity of making and maintaining the cutters may have something to do with it.
     
  10. wefalck

    wefalck Registered User

    Mar 29, 2011
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    Male
    Paris
    Nice toy you found there, James.

    Gear hobs were used in the Swiss watchmaking industry. A company that made both, hobs and machines was/is(?) MORAD. I saw a hob on the German ebay this morning, but can't find it again now. Essentially they look like normal hobs, but are shorter, i.e. they are only some 8 mm long, and wood fit on to the arbors you would use for gear cutters etc. I have one here that I bought years ago, thinking from the photo on ebay that it was a simple milling cutter.

    In the normal hobbing process the hob would be forced into the blank that is rotated in a fixed ratio to the rotating hob. I suppose one could also hob a pre-gashed wheel, i.e. using the hob as a sort of rounding-up cutter.

    Here is a Web-site (in German unfortunately) where the guy describes how he makes his own hobs and uses them: http://www.metallmodellbau.de/GEAR-CUTTING.php

    wefalck
     
  11. bkerr

    bkerr Registered User
    NAWCC Member

    Nov 29, 2007
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    Canal Fulton,OH
    Very interesting tool, thanks for posting
     
  12. motormaker

    motormaker Registered User

    Apr 5, 2010
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    Tucson, AZ
    wefalck,
    Yes , that web page describes/shows things pretty well. You can have your browser translate the text then read and correct mistranslations by hand.
    Jim
     
  13. Bob Murray

    Bob Murray Registered User

    Aug 15, 2011
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    Tarasov's "Technology of Watch Production" has a section on hobs and hobbing. The Russians seem to have done quite a bit in their watch industry.

    Regards,
    Bob
     
  14. Watchfixer

    Watchfixer Registered User

    Jun 11, 2011
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    TV repair tech.
    Will your hobber machine hob a involute teeth shape, also cut an epicycloidal teeth? For pinion gears with rounded tips what is cutter shape used, I think would that not be possible using a screw hobber to do this pinions gears?

    you see, I'm learning what is done.

    Cheers, Watchfixer
     
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