English PW Help Fusee mainspring

Discussion in 'Watch Repair' started by Buffomarinus, Sep 14, 2020 at 10:50 PM.

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  1. Buffomarinus

    Buffomarinus Registered User

    Mar 7, 2020
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    G'Day,

    I'm in the process of restoring an English fusee movement made by F.P. Adams. I've actually turned up a reasonable case from brass stock. The movement works great, but I'm having problems with the original mainspring (old and brittle). I'm looking at substituting a new Waltham 18s #2205 (JA-705) for the original spring as it has similar dimensions to the original. Any thoughts or suggestions on this negative or positive?

    Cheers,

    Rob FNQ,Au
     
  2. gmorse

    gmorse Registered User
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    Hi Rob,

    You should certainly replace that spring, but first measure the height and thickness of the old spring, the I/D, inside height and arbor diameter of the barrel, then go and look at David Boettcher's website on mainsprings, where there are several helpful calculators as well as much useful information. Whilst you may not be able to find an exact match, it doesn't matter too much if the height is a little less, (but clearly not more), the strength of the spring is proportional to that, but since it's also proportional to the cube of the thickness, that's more critical. You'll probably have to get a spring that's too long and cut it down.

    Depending on the date of your movement, it may have a rectangular hook riveted into the outer end of the spring, which engages with a cut-out in the wall, or if made later it may just have a hole-end spring with the hook in the barrel wall.

    Regards,

    Graham
     
  3. Buffomarinus

    Buffomarinus Registered User

    Mar 7, 2020
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    G'Day Graham,

    Thanks for the excellent response.

    I ran the suggested calculations and the Waltham #2205 is close to the right length (533mm) and pretty much spot on with the width of the original (3mm). The main drawback is the "strength." The original spring has a thickness/strength of .270mm where the #2205 max available is .225. I guess I could get around this by cranking up the initial mainspring "set up" on the fusee movement?

    No problem with the spring end as I can probably modify the original barrel to take the "T" end or make up a rectangular hook for the Waltham spring that will fit the current attachment point on the outer rim of the barrel. I made a new hook for the original mainspring that worked a treat until the spring broke two weeks later at another point.

    A couple more questions... Does anyone make and sell new springs for these old fusee movements? Is it possible to "reset" a used watch mainspring through heat and tempering?

    I swore I would never get involved with fusee movements, but after mucking about with the Adams and getting it up and running, I'm "hooked" on the buggers! Many of the English fusee movements are literally "works of art."

    Thanks again,

    Rob

    FarNorthQueensland, Australia

    Run1.jpg
     
  4. gmorse

    gmorse Registered User
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    Hi Rob,

    These old springs were often too thick in my opinion, so 0.225 should do the job well enough. The initial setup is a matter of trial and error once the spring has been fully wound and run down a few times. See what David's calculators predict using these parameters, especially for the necessary length.

    A definite 'NO' to the first option, the new part must be modified to fit the watch, never the other way round; the second option is the right way.

    Not that I'm aware of, and I guess it's possible to 'reset' an old spring, if you have the equipment to manage very precise temperature control and the knowledge of how that particular steel responds to it. The latter issue is the hard part. I really doubt if it's worth the effort, although experimenting is a interesting path to follow if you have enough old springs.

    Regards,

    Graham
     
  5. Skutt50

    Skutt50 Registered User

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    Just some thought regarding this:

    Hardening by heating to cherry red (loss of magnetic ability) should be the same for all mainsprings. The tempering could be done by observing the color change in the steel. My thought is that by noting the original color of the spring, a tempering to the same color would yield the correct strength.
    As Graham pointed out you would need an oven with precise temperature control...... Perhaps not worth the effort.....
     
  6. Jerry Kieffer

    Jerry Kieffer Registered User
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    Rob
    Even if they did , you would probable would not get what you wished since many are of various sizes with no real standards.

    Personally, I find it easier to just make what is needed since it is not much of an issue.

    While there are many alloys available, I generally use 1095 blue spring steel shim stock of the highest quality from a reputable supplier.

    I shear it a little wider than required and then coil it up in a washer. It is then placed on a magnetic chuck in a small milling machine and ground to exact width per attached photo setup. In the photo, I did not have a main spring photo example, but the setup is identical to the wheel setup shown in the photo. From this point the length is trimmed and the ends are addressed.

    Jerry Kieffer

    fullsizeoutput_39e.jpeg
     
  7. Buffomarinus

    Buffomarinus Registered User

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    Wow, some excellent advice from all. Thanks guys!

    Question for Jerry... I'm not familiar with "spring steel" shim stock. After machining, do you then have to heat and temper the spring? I do have access to a small temperature controlled oven/furnace.

    Graham, from a collector's standpoint, I do agree with you about modifying original bits to suit the newer, available parts. The thing is that the original barrel has been flogged a bit and doesn't run true. The arbor bearing holes are also slightly out of round from wear. The most efficient thing for me is to turn up a new barrel on the mini lathe and match the spring attachment with the available spring. The mod would only involve a tiny hole in the bottom of the barrel and a equally tiny notch in the cap.

    With this movement, it will be mounted in a DIY brass case. I am tempted to to turn up a perspex case to show off the "beauty in motion" of these English fusee movements. An original case would be great, but they are as scarce as the proverbial "hen's teeth," often in poor condition and generally out of my price range.

    Thanks again gang,

    Rob

    FNQ,Au
     
  8. Jerry Kieffer

    Jerry Kieffer Registered User
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    Rob
    Unfortunately I am not familiar with what is available in Australia.

    In the US, Blue tempered spring shim stock is available already hardened and tempered. The following link is one example from Mcmaster Carr that I believe ships world wide.
    McMaster-Carr

    There are of course many other sources.

    Jerry Kieffer
     
  9. Buffomarinus

    Buffomarinus Registered User

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    G'Day Jerry,

    I would imagine that spring steel shim stock would be available here in "OZ." I'll have a look at the U.S. link you kindly provided and then search here for a local source of the same material.

    Also, thanks for passing on your method of machining down the spring width. This technique will be very useful for several watch projects I have on the go.

    Cheers,

    Rob

    FNQ,Au
     
  10. gmorse

    gmorse Registered User
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    Hi Rob,

    I would set the barrel up in the mandrel and re-bush it so that it runs true, only making a new barrel as a last resort.

    Barrels are usually retrievable even if they initially look wrecked. I did use a 'belt & braces' approach in this one, but the steel sleeve probably wasn't necessary:

    DSCF4703.JPG DSCF4707.JPG DSCF4713.JPG DSCF4723.JPG DSCF4736.JPG

    The new hooking point was made at 180˚ to the repaired section.

    Regards,

    Graham
     
  11. Jerry Kieffer

    Jerry Kieffer Registered User
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    Graham

    Barrels such as those in your first photo can be silver soldered where the strength of the repair will equal or exceed that of the original condition.

    In doing this, I first machine silver solder down to a size appropriate for the size of the repair per first photo. The sample in this case can be seen in comparison to a hair spring.

    Next I use a Oxygen/ acetylene micro torch with a micro tip of .003"-.005".
    Flame size comparison can be seen in the second photo. The repairs are done under magnification and are generally invisible after clean up.

    Jerry Kieffer

    fullsizeoutput_399.jpeg DSCN1176.jpg
     
  12. Buffomarinus

    Buffomarinus Registered User

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  13. Karl Burghart

    Karl Burghart Registered User
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    Jerry,
    I like the idea of making the mainspring. How do you shear the shim stock?
    Thanks,
    Karl
     
  14. Jerry Kieffer

    Jerry Kieffer Registered User
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    Karl
    With a small heavy duty quality shear. Photo example

    Jerry Kieffer

    fullsizeoutput_6d2.jpeg
     

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