gear cutting/repair

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  • #48016
    pkamargo
    Participant
    • Topics Started: 14
    • Total Posts: 62

    Hello!
    I am not new to clock repair, I am in this business for many years and I specialized repairing and restoring anniversary clocks.
    But I purchased the course because of the lathe lessons, I am limited knowledge about this and got precious information on the videos. (soon I will not need to send some jobs to other people to do)
    Now, as much I had browsed around some videos I didn’t see anything about repairing damaged gears. Sometimes it is absolutely impossible to find an original replacement and all you can do is to make a new gear or make an insert to replace a broken tooth…

    And things go even more difficult when we go into the small ones. Let me detail the case I need help.
    A customer brought to me a very small and old – securely more than 100 years old – french carriage clock to repair and restore. Time only, 8 day, unsigned.
    There are two broken pivots and I also noticed a pivot that was made out of center… These are common tasks to fix.
    But the second wheel is well damaged and it is not that ordinary flat gear – I am not sure how to name it, the teeth are in right angle to mesh the escape pinion, like the older Morbier/Comtoise clocks with verge escapement.
    Looks like someone has forced it… all teeth were bent to a 45° angle.
    Well, using a little screwdriver as lever I got to unbend them, just one broke. There are (well, were…) 60 teeth and the out diameter of wheel is about 11mm.


    All teeth still need some reshaping, and the broken one needs to be replaced with an insert. I just don’t know HOW can I perform this in such a small gear!
    I don’t have micro tools… Where can I get or how can I make them?

    Last case, I see it is possible to remove all teeth and cut new, because the wheel diameter will not change and there is enough height. But I think it will be expensive to find the exact gear cutter and I don’t know how to make one. I remember I saw a video on Youtube long time ago; a guy made a fly cutter to make a new gear for a watch, much smaller than this. But I can’t find it again. ( and while searching for this video I found your course, and here am I )

    Any help, please!

    #50442
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Hi pkamargo and welcome to the forum!

    Yep that wheel is a mess! Pretty hard to repair as I’m guessing the damage to the teeth is on the side that engages the escape pinion teeth. If not it still going to look really bad. You can repair individual teeth but it’s always been easier for me to cut out a section of three or more teeth, insert a blank which can then be machined and new teeth cut. Making a new contrate wheel isn’t all that difficult but does require some special tooling. Wheel cutting is something I plan to cover in the future but to describe it here would take quite a while. Making a fly cutter is relatively easy also.
    There are a few people out there that cover the subject in detail up on their websites. I believe John Shadle has some info cutting a contrate wheel and csparks I know covers making cutters. I’ll check around their sites and will come back with links to the exact pages. If I’m wrong then I’ll try to find some info for you and will post something up here.

    be back in a bit with something,
    Bob

    #50443
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Hi pkaMargo,
    Give these links a try. Some really good info. on both websites.
    csparks covers making cutters.

    http://www.onlineclockbuilding.com/OCB2/2notes0128.html

    http://www.csparks.com/watchmaking/WheelCutting.html

    Enjoy!
    Bob

    #50444
    pkamargo
    Participant
    • Topics Started: 14
    • Total Posts: 62

    Hi Bob!

    So this is called a contrate wheel.
    If you think the pictures I posted are looking bad, imagine it before I lift the teeth up!

    Well, even before reading your reply I decided to start something, will make a new wheel.
    First step I used a brass part that was almost the desired size to turn a blank exactly the same dimensions of original wheel:


    Already left a drilled center hole to fit the arbor.

    Second step I made a fly cutter using a broken HSS drill and a clock post to hold it:

    I tested it with a piece of brass sheet and the cut it makes matches almost perfectly with original teeth gap. Some final adjust and finish needed before go to the wheel blank.

    Third step, a divide device to count the 60 teeth.
    Improvisation department activated, I mounted a large 60 teeth gear on a brass tube with center hole matching the wheel blank arbor. Then I used a thick piece of wood to place the tube so it can turn with a little friction, and a click to lock each tooth. (No picture avaiable now, camera batteries discharged…)
    All this will be put together in the lathe and hopefully I will succeed cutting the wheel blank.

    About the links you posted, great stuff! The second one is exactly what I was trying to find – and my memory tricked me, it was not an youtube video… Thank you!

    #50445
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Now that’s creativity pkamargo!!
    Thanks for posting the pics.
    Please keep us posted on this project.
    and keep having FUN!
    Bob

    #50446
    pkamargo
    Participant
    • Topics Started: 14
    • Total Posts: 62

    Hi everybody! Back to this topic to tell the news.

    I paused this project for some time to do easier work on other clocks – and make some money :D

    Then I came back to it. Well, here are the pics of the things put together on the lathe (1st version):

    The first and second attempts to cut the contrate wheel failed. This structure was not good enough to hold the blank.
    In the first attempt the teeth were not cut at the same height, so I added a screw under the blank holder to keep it in place.

    In the second attempt the teeth were not cut with the same width. The blank holder was too tall and was side moving with the lathe vibration and the cutter strokes. So I added a second wood layer to hold it closer to the cutter, this way:

    Third attempt… I was tired, these days are very HOT (summer here) temperature about 30°C. Repetitive work and discomfortable body position causing some pain in my neck and arms…
    -position the blank
    -lathe on
    -sloooowwwwlyyy feed the blank trough cutter
    -lathe off
    -return blank and move to next tooth
    -lathe on…..
    After almost two hours… – TADAAAA!!! Perfect!

    Next pic shows the cut wheel after cleaning, removing burrs and polishment:

    I still need to cut it out of brass rod and install in the arbor. But even after this I won’t be able to test it because the escape wheel has a broken pivot. This is another subject I will leave to someone else to do because it is an extremely thin pivot – about 0.1mm!

    #50447
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Great post and pics pkamargo!!!
    The wheel looks beautiful.
    You’ve proven that ingenuity is everything in this field. VERY CREATIVE tooling set up!
    I believe that if you didn’t have that lathe you still would have figured out a way to cut that wheel!

    Thanks for starting and posting such a helpful thread pkamargo. I’ve really enjoyed it.

    I don’t need to say have fun as I know you aready are.
    Please keep them coming!
    Bob

    #50448
    pkamargo
    Participant
    • Topics Started: 14
    • Total Posts: 62

    Thank you for your words, Bob!
    I really enjoyed the adventure of making these tools and the final result. Will come back again later to show the clock assembled and – hopefully – in running condition. :)

    #50449
    pkamargo
    Participant
    • Topics Started: 14
    • Total Posts: 62

    UPDATING

    OK, I received the pivoted parts and now I could finally put all together test the contrate wheel I made.

    And here is the result: after all disaster it suffered and now after my repair job CLOCK IS RUNNING AGAIN!!! :D /

    I am happy that I suceeded ressurrecting this little old movement, and I believe that my customer will be very happy too.

    Now I just need wait for the porcelain dial come back from the restorer in Australia and the clock will be ready to return to my customer – practically in brand new condition.

    #50450
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Congratulations Pkamargo!
    Thanks for sharing this project up here. It’s been fun and educational for all of us.
    Looking forward to another one from you!

    Bob

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pkamargogear cutting/repair