How to remove gear / cam from shaft ?

Discussion in 'Clock Repair' started by Doug Henry, Dec 28, 2006.

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  1. Doug Henry

    Doug Henry Registered User

    Jul 25, 2005
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    Need to remove the 1/4 hour gear/cam on the front of the movement. This is the four pointed 'star' cam that releases the melody each quarter hour. I assume it is pressed on. (Please be patient, I do not know the proper lingo).

    Movement is a Cuckoo Clock Co., mantel, spring driven, triple chime unit.

    I want to remove the minute shaft to replace the busing on the front plate and not damage anything as I don't believe replacement parts are an option.

    Then, how is this piece secured to the shaft when reassembled?
     
  2. RJSoftware

    RJSoftware Registered User

    Apr 15, 2005
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    I'd like to know this as well.

    I ruined a friction fit small gear that was part of the motion works (gears that advance the hands).

    I tried to grip the gear with pliars and twist the shaft to slide the gear off.

    Well,,, the teeth just crumbled. Arhhhkk.!

    Now I have to get a matching gear cut.

    I wonder if I should have heated the arbor and that might have helped.

    RJ
     
  3. David Robertson

    David Robertson Registered User

    Jan 6, 2003
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    One technique that often works...

    Get two paint can openers. Place under the cam/gear.. one on each side. Pry EVENLY from each side (otherwise you can bend arbor). Cam/gear comes off.

    If cam/gear is too far from plate to get good leverage, use two equal spacers.. small bits of flat brass, aluminum, wood, etc.

    A similar technique that will get in a thinner space is to use two IDENTICAL sized scredrivers. Insert from opposite sides and twist blades at same time so as not to put uneven pressure on arbor and end it. Think about how forces are being applies and do it is a manner that makes equal forces on opposite sides.

    Trying to twist and pull is courting with disaster.

    David
     
  4. bchaps

    bchaps Registered User

    Dec 16, 2001
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    I do not normally remove the star cam....removed one from a Hermle 340-020 and bent the arbor. There is a tool specifically made to remove the star cam, but it's quite expensive. Normally, this pivot hole is not excessively worn, at least not worn enough to risk damage to the arbor or cam.

    Bill
     
  5. Doug Henry

    Doug Henry Registered User

    Jul 25, 2005
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    Assuming I get it off. Will it be loose when reassembled?

    If so, how do you tighten it's grip on the shaft?
     
  6. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
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    Leave it on if there is no reason to remove it.
    To remove it, drill a hole the size of the front end of the arbor and about 5mm shorter, in a bit of brass or steel rod.

    Place a piece of tubing over the inner end to hold the place, then tap the drilled bar on to the arbor so the cannon pinion comes off.

    It will still be tight when you replace it.
     
  7. doc_fields

    doc_fields Registered User

    Sep 29, 2004
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    Wiha makes a chip-lifter tool for use in removing ic chips on electronic boards. I have a few of these, and use them to help remove these cams and other sundry items. They have a nice curve at the bottom, and thin edges to work under things, much like the old tack remover tools. Sometimes I have to heat the cam to get it to pop loose. When I do that, I place the nut back on the shaft so the cam doesn't become an airborne hot object to land in my lap or worse. I also possess and use the Star cam puller, which is great for most items, except for the cams on an Urgos movement. I think those little wretches are heated red hot, then pressed on under great duress, so they bond molecularly to the shaft. But, in reality, I do heat them to get them off, and it works pretty good with using the Wiha chip lifters......doc
     
  8. David Robertson

    David Robertson Registered User

    Jan 6, 2003
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    Doug,

    Things that are press fit on a smooth shaft (like the cams and gears we are discussing) will usually press back on and be sufficiently tight to serve their purpose.

    When a shaft has been roughed up to create a tighter seat for something that is pressed on, it will often loosen enough in removal to be difficult to re-attach tightly enough without some additional roughing of the shaft.

    David
     
  9. Tom Kloss

    Tom Kloss Registered User
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    Dec 5, 2003
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    For the life of me I can't figure out why these star cams are all assembled with such a tight press fit. I know you wouldn't want them to slip but these seem to be pressed on in defiance of the repair people. I'm with Mike and Bill unless it an absolute must, better left alone.

    Tom Kloss :frown:

    "Sometimes you really don't know if your being rewarded or punished"
     
  10. Joseph Bautsch

    Joseph Bautsch Registered User
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    Dec 9, 2006
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    I agree with Bill. Unless that pivot hole is worn to the extent that it is causing problems with the clock running properly I would leave it alone. As you can see from other replies to your question removing and replacing that cam is a big problem. In most cases it's not worth the risk of creating more damage and more problems trying to repair it.
     
  11. Doug Henry

    Doug Henry Registered User

    Jul 25, 2005
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    Thanks for in information and expertise. Great info to keep on hand.

    Sounds like I will leave as is. The amount of wear does not affect the angel of the pivot on the rear plate. That rear pivot is the gear end and I will it replace due to wear.

    I have ordered a set of Swiss broaches, smoothers, bushings etc. and made a center finder and push in tool. I will make Lexan plates grooved to hold the movement plates in a vice. The vice is mounted on a bench top metal lathe / mill machine for cutting holes, press bushings, resurface etc..

    Second question:
    What do you use to polish the pivots?

    Steel wool, wood, Crocus cloth?
     
  12. David Robertson

    David Robertson Registered User

    Jan 6, 2003
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    Doug,

    Pivot polishing is done with a burnisher. Pits and grooves are removed with a pivot file. Both are available from the usual suppliers.

    Dave LaBounty has an excellent article on his web site here.

    David
     
  13. JB

    JB Registered User
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    Dec 27, 2006
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    Have a similiar problem. But with a cam for the silent/chime lever. To make a long story short it popped off. I put it back on , but popped off after awhile. I was thinking of using a drop of LOC-tite and letting it sit for a day. I don't know if roughing it up would work the spring seems to put a fair bit of tension on it.
    Thanks
     
  14. doc_fields

    doc_fields Registered User

    Sep 29, 2004
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    Here's the Wiha tool I mentioned earlier........

    231.jpg

    232.jpg

    First pic shows the tip, second shows handle with Wiha part number, third shows side view of the tip.

    For what it's worth..........doc

    233.jpg
     
  15. Mike Dempsey

    Mike Dempsey Registered User
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    Jul 8, 2006
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    These star cams are very easy to remove with a drill press. Support the plate on the bottom with 2 wooden blocks. Chuck the shaft in the Jacobs chuck about 1/4" from the cam. Use the hand wheel to press off the star cam. This works very well. To replace I use one of the old hot popcorn poppers to heat up the cam. After a few minutes, use a pair of tweezers to drop it on the shaft. This works about 90% of the time.
     
  16. Doug Henry

    Doug Henry Registered User

    Jul 25, 2005
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    David: Great write-up on pivots. Glad I read that before going further. Ran to the auto parts store for Simichrome but they don't carry it, settled for Blue Magic metal polish. It does a very nice job with a piece of wood on the coated pivots.

    Thanks for all the methods to remove the star cam. Mike: great meathod, drill press keeps the shaft from bending.

    Thanks to everone.
     
  17. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
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    Doug
    The problem with using things like abrasive paper and Dremel stones to polish pivots rather than using a file and burnisher is that they do not get right into the corner as a file and burnisher, which are undercut by 10 degrees or so.

    The front centre arbor is at the opposite end of its thrust - the cemtre pinion is always at the back, and the front has a large diameter pivot, so does not wear much.

    Make sure the spring is tensioned enough when you put the centre wheel back on, and oil the front pivot then, before assembling the movement.
     
  18. Tunderer

    Tunderer Registered User

    Nov 5, 2003
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    Removing star cams with a drill press will work if there is room enough for the chuck. There is a risk that the hard jaws could mar the soft shaft. The trick is to realize the shaft needs to be supported right down next to the cam. Any thing else risks bending it. I built a set of clamp tools in aluminum. I machine screwed two pieces together with paper between them. I then drilled a hole down the center to match the shaft. The screws clamp the tool together on the shaft then I push it with my mini arbor press. No bent shafts. No damaged hand nut threads. I have an assortment of back up blocks I use to support the back side of the plate close to the shaft so there is no distortion in the plate. It doesn't usually take much pressure. My arbor press started life as a french fry maker. If necessary I reposition to finish the job.
     
  19. bangster

    bangster Moderator
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    Jan 1, 2005
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    A while back I had trouble removing a pressed-on setting knob on an alarm clock. Wouldn't budge. I finally went out to the garage and got a slide hammer. THAT took the sucker off. Which gave me an idea...build a smaller slide hammer, for use on clocks. Here's the result.

    317.jpg

    Piece of 1/2" copper pipe, and a cap. Poured it full of melted lead from discarded wheel weights (free at your local tire store). Soldered cap on. Drilled hole lengthwise. Threaded a rod on both ends. Soldered a nut onto the bottom end, with a holding handle of copper wire. Fabricated the top hook out of the long side of an "L" brace, and attached it with two nuts. It hasn't yet been fired in anger, but I'm willing to bet it will do what it's supposed to...pull off pressed-fit parts, without denting the part screwdrivers and pry-bars fulcrum against.

    bangster
     
  20. doc_fields

    doc_fields Registered User

    Sep 29, 2004
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    It occurred to me last night (while working on an Urgos movement whose minute hand shaft had wobbled an oval hole in the back plate) of how can you burnish the pivot of this shaft if it's still stuck in the front plate with the star cam on it? All the more reason for me to remove the star cam so this can be done.

    Bangster, have you used your slide hammer on a star cam yet? I'd be interested to know how it went if you did. Some of the Urgos cams are on pretty solid. Regards..........doc
     
  21. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
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    Good idea, Bang!
    Gathering pallets and hammer bosses et al.
    A lot of the star cams only leave a very small gap between them and the front plate, though. 1mm or less.
    With those, there is no way you could get one off by getting under it - you would have to tap the arbor out.
    Me - I leave them in, unless there is a very good reason to remove them.
     
  22. bangster

    bangster Moderator
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    #22 bangster, Jan 4, 2007
    Last edited by a moderator: Dec 7, 2017
    Nope. I don't own a three-train with a pressed on star cam. Sorry.

    bangster
     
  23. harold bain

    harold bain Registered User
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    Nov 4, 2002
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    Bang, neat little tool. Did you harden it at all to prevent it from bending in use?
    Harold
     

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