Hello Folks,
I posted this query at the NAWCC BB but haven't received any reply yet, so I thought I'd try here, too.
I am trying to find a replacement mainspring for a 0 size pendant watch, made (apparently by Agassiz) for Rowe Brothers (apparently a Chicago jeweler) in the 1880s. The spring has the following dimensions:

1.6mm wide; 0.14mm thick; about 15.125" long

The spring has a normal rectangular hole at the end (no "T" end, etc.) that has broken at the very end (outter side) so that it cannot latch onto the hook on the inside of the barrel wall. If anyone can tell me what size, type, number, etc., of mainspring I should look for/order, I'd be very grateful. Thanks,
Pete Belmonte
Ofallon, IL

Pete,

Looking at my mainspring info, bestfit makes a white-a-loy mainspring #78P which has the following dimensions - 1.60mm x .14mm x 13.5in (dennison=7x8x13.5), This is as close I can find in their system. You can contact any bestfit dealer including LaRose and ask them for springs meeting your specified dimensions and they should be able to find one if it is still being made or in stock.

One thing that you may need to do is modify the holes to suit the size of the barrel and arbor spurs.

Hope that this is helpful.

Mike,
Thanks very much for the info. Ofrei has #78P, and I have a request in with S. Larose to see what they have. Question: Will the length difference make much difference (13.5" vs. 15.125")? Can I use the 13.5" spring just as well as the other? Thanks again for your help,
Pete Belmonte

The shorter spring will somewhat dimminish the run-time. It's hard to say by how much. However it is the closest length I could find that has the same thickness and strength as yours. An Agassiz movement should handle the white-a-loy (which some report to be stronger than the old blue-steel stock) spring without much problem.

Another solution would be to drill and shape a new hole in the old mainspring to fit into the barrel hook. From your description, it sounds like this would shorten the spring very little. However, if the spring is old and "set," it might have very little power left at the end of the run-time.

Thanks Mike,
I already tried to put a hole in the end of the old spring; I don't have a small enough drill bit, so I tried to gently push through a hole using the tip of a small nail, but the spring broke off another 1/4" or so.
S. Larose has only the "tongue-end" springs in my size; Ofrei says they don't have anything that size. Question:
Does the #78P have a hole end for certain?
What are the Dennison numbers for a narrower (not thinner) spring, say 1.5mm (or even 1.4mm) wide, 0.14mm thick, about 15" long?
What will the effect be if I use such a spring? Will it damage the watch, or is it simply a matter of efficiency? If it is only an efficiency concern, I don't mind; the watch is mine and I simply want to see if I can get it running again.
Thanks again for your help,
Pete

I looked up the 78P in anothe table and it seems to have a tongue end, so it would need some retrofitting. Small, pivot drill bits will work for making the hole, and needle files for final shaping.

You are having a problem that there isn't an easy fix for. Many of the swiss movements didn't use standard or mass produced parts, making replacement and fixing sometimes difficult. I also don't see anything close to this size in any American mainspring lists.

As for a narrower spring... It isn't advisable to use one narrower than intended. This can cause some problems with keeping the spring attached to the barrel and arbor hooks.

I wish I could offer more help. Is there anyone else who can offer some more advise for Peter?

Just a tip on drilling, punching or reforming an old mainspring end. You must remove the temper from the spring (only at the end portion you are working with). Simply heat the end and let it cool at room temperature. This removes the brittleness and the spring can now be bent, drilled, etc. without breaking.

Thanks Kenny and Mike,
I might have another try at putting another hole into the old spring (appears to be a bit "set" anyway). I didn't even think about removing the temper first--good advice.
In the meantime, if anyone knows of other possible supply sources, or has any other ideas, I'll be glad to listen. Thanks again for your help,
Pete

Folks,
Well, I successfully removed the temper from the mainspring, but the rest didn't go so well. As I said, I don't have the proper tools, and the result my efforts was less than satisfactory. This mainspring is fairly well set anyway.
So, I will clean the watch and await a mainspring. In the meantime I'll keep working on the Elgin 16s and Arnex watches that I've had some success with! Thanks again for your help,
Pete

Peter,

Do keep us posted. I have many drawers filled with watches awaiting wither parts or experience or both.

Thanks Mike,
I have re-installed the old mainspring and started cleaning the movement; I'll put the watch back together and await a new mainspring (or proper drilling tools, whichever comes first). I also submitted an "item wanted" request on another MB; we'll see what happens. The watch in question was my grandfather's; he used it as a small pocket watch. I know it hasn't been used in at least 50 years, so I thought I'd try to get it running (it looks like the mainspring is the only problem...). I have his "nice" pocket watch, too, a 6s Elgin in a beautiful multi-color gold case, but I don't want to mess with that one, it works fine .
Thanks again,
Pete

Folks,
An update for those following this saga :
I've got the movement (mostly) reassembled; now it appears that the balance has excessive "wobble," and I fear that one of the balance pivots is broken or bent. They both look fine, but the balance didn't wobble before, and I wonder if I've broken a pivot during reassembly. I will also check the jewels more closely. (While disassembling this movement, I didn't take the balance assembly off the balance bridge.) If the staff is indeed broken, I will have to await parts AND expertise!
Also, since the mainspring is broken at the very end, there is sufficient friction and force to partially wind the spring.
Sincerely,
Pete Belmonte