What's a frog?

Discussion in 'Clock Repair' started by Willie X, Sep 23, 2019.

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  1. Willie X

    Willie X Registered User

    Feb 9, 2008
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    Someone asked for more information about what a 'frog' is. So here's a photo and a quick description on how to use a frog.

    In machinery a frog is often some kind of stop. Usually it's rather hefty with no chance that any amount of battering will ever have a chance of moving da frog.

    In clock work the frog is simply a holder or clamp. It is designed to hold a part in a fixed position where it can not budge while you work a surface to flat. It can be used to make or resurface a flat surface on just about anything but for clocks it's mainly used to adjust and/or resurface the impulse surfaces on deadbeat escapement pallets.

    The best way I've found to do this is to use regular wet and dry automotive sandpaper on a piece of 1/4" plate glass. Glass is good because it's flat and will not wear or deform in normal use. A 6" x 12" piece works good for me.

    The sandpaper is cut into long strips about 2" wide then stretched and taped tightly down the center of the glass. 220, 320, 400, and 800 grit sandpapers are good for starters. About 90% of the actual cutting will be done with the coarser grade and you can progress quickly through the finner grades. Always finish a grade using strokes that are in line with the escape wheel tooth travel.

    During all this, the two adjustable feet on the back side of the frog are rubbing against the glass while the work is being rubbing on the sandpaper strip. I use a small pool of machine oil on the paper and a lot of action with very little downward pressure.

    Setting up your work and adjusting everything may take a while but I think it will be obvious once you get started.

    Good luck, Willie X
    20170402_112712.jpg
     
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  2. shutterbug

    shutterbug Moderator
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    Do you have to make that critter, or can they be purchased? I've always used a smooth jawed bench clamp to hold the impulse face flush with the surface, and then use the "sandpaper on a stick" to surface it. Got that idea from David LaBounty. Your idea might be easier.
     
  3. gmorse

    gmorse Registered User
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    Also known as a bolt tool, and I've never seen one for sale commercially; I made both of my watch-sized tools.
     
  4. Bruce Alexander

    Bruce Alexander Registered User
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    That's the method I currently use too SB. Depending upon the quality of your vise or bench clamp (mine is pretty cheap with a lot of slop), I think that Willie's Frog would allow one to perhaps get more precise angles and sharper lines. At least in my hands/shop I think it would.

    Jerry Kieffer details the use of a Mill to finish impulse angles. YIKES!!! I can see myself completely destroying a Verge attempting that although Jerry makes it look easy.... of course.

    Neat looking tool there Willie. I remember that conversation and also wondered what a "Frog" was. Thanks for sharing some of your knowledge.

    Regards,

    Bruce
     
  5. Jerry Kieffer

    Jerry Kieffer Registered User
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    Hey Willie
    Assuming this devise is yours, have you ever considered installing a roller on the rear and use a standard oil stone?

    Bruce
    Actually grinding on the mill is safer and more controllable than most hand methods properly approached. If I can do it anyone can.

    Jerry Kieffer
     
  6. John MacArthur

    John MacArthur Registered User
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    Here are a couple of mine - used exclusively for screw head polishing. The height of polishing is adjusted by the outboard screws, which have locknuts. I have several others of different sizes. I like the idea of Willie's clamp system for other things than screws - might have to make a couple....
    Johnny

    53.3.jpg
     
  7. Willie X

    Willie X Registered User

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    I only had one photo (bottom side) of my frog but the holes are threaded and have locknuts on the top side tjat work just like john's frogs.

    I have used mine with several stones. All you need to do is make a spacer that will raise the glass (or other hard surface) to the height of the stone. Fine adjustments can be made with the feet. I like the sandpaper because it's always nice and flat.

    It can also be used with a vertical belt sander but that is a little too fast for my likeing.

    WIllie X
     
  8. bangster

    bangster Moderator
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    I still don't understand what a frog is, or does, or how those doodads work.
     
  9. gmorse

    gmorse Registered User
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    Hi bangster,

    The first picture shows the tool as you'd use it, with the screw or other part to be finished clamped at one end and the two levelling screws at the other. It sits on the glass or grindstone and by adjusting the two levellers you can arrive at a flat surface on the part clamped in the jaws so that it's ground flat. I usually use progressively finer grades of 3M lapping film on glass for the final finish.

    Bolt Tool Top.JPG

    This is the underside,

    Bolt Tool Underside.JPG

    and a close up.

    Bolt Tool Closeup.JPG

    To achieve a flat polish on larger or irregular shaped parts such as springs, they can be fixed to the underside with shellac.

    Regards,

    Graham
     
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  10. Bruce Alexander

    Bruce Alexander Registered User
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    #10 Bruce Alexander, Sep 25, 2019
    Last edited: Sep 25, 2019
    I'm glad you asked that bangster. I was beginning to think that it was just me. :)
    While looking through the Archives to find the person who had asked the question recently I happened upon this excellent discussion on the use of a Frog to reface pallets: Refacing pallets - direction of filing?

    I'm quoting Matt here so hopefully he'll get an alert and see this thread:
     
  11. bangster

    bangster Moderator
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  12. Bruce Alexander

    Bruce Alexander Registered User
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    :???::?|:???:
     
  13. RJSoftware

    RJSoftware Registered User

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    same principles as Crocker graver tool. A device that holds an object at a desired angle so it can be precisely round/polished.
     
  14. D.th.munroe

    D.th.munroe Registered User

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    I noticed years ago Perrins in Canada had these for sale, maybe a bergeon, but labelled as a "pallet adjustment tool"
     
  15. shutterbug

    shutterbug Moderator
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    I've seen similar modern devices made for sharpening knives/screwdriver blades. They would probably work too.
     
  16. kologha

    kologha Registered User

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    A frog is also the thing that is attached to a soldiers belt and which carries his bayonet!
     

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