Mainspring Installation With T-end

James Wrobel

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Jan 17, 2020
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When installing a mainspring with a T-end from factory packaging, I'm finding it difficult to get the T-end in the hole at the bottom of the barrel. The hole is very small, and once the spring is released in the barrel, it doesn't want to twist into place.

With a tongue end, a mainspring seems to be able to slide its way along the side of the barrel and catch when the watch is wound, but with a T-end, the barrel cover won't go on until that nub on the end is in the bottom hole.

Are there any tricks to accomplish this?

Thanks,
jjw
 

Skutt50

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Mar 14, 2008
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I insert the spring with the T-end almost above the hole or slightly "after" the hole. Then it usually is not a problem to push the T-end backwards into the hole...
 

James Wrobel

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Both good ideas. I was putting the T-end in slightly "before" the hole and hoping I could wind it in. Obviously not right.

For the first idea, a straw from a spray can might do the trick.

Thanks,
jjw
 

Al J

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Jul 21, 2009
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I usually take them out of the shipping ring, wind them up in a winder, leaving the end of the spring out. I can then position the tee end in the hole of the barrel drum easily, and hold it there with tweezers while I press the spring out of the winder.

I would be cautious with installing it and then "pushing" the tee end to get to the hole - I've tried this and found the tee end can gouge up the floor of the barrel drum.

Cheers, Al
 

James Wrobel

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I have to admit that I have never successfully pushed a spring out of the shipping ring and into the barrel. The way they package the spring, it's such a tight fit, and it just never goes in right for me.

jjw
 

Al J

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I have to admit that I have never successfully pushed a spring out of the shipping ring and into the barrel. The way they package the spring, it's such a tight fit, and it just never goes in right for me.

jjw

If the spring is actually designed for the caliber in question specifically, it should be wound up small enough to give you adequate clearance. I do this every day without issue, but mostly on watches where the spring is specific to the caliber. If you are buying generic springs, then yes there's a chance they can be very tight, or simply just too big., That and for special ends are really the only times I use a winder.

One thing I do it take the back end of my tweezers and press the spring flat the the shipping ring after I set it on top of the barrel. Then I can use my tweezers to move the ring side to side to get a feel for how much clearance there is. I make sure the spring is centered in the opening this way, and then press down pretty firmly with the back of the tweezers as I press the spring in with a small brass tool I made. If the space it tight, I press hard enough to sort of limit the expansion of the spring until I can press on either side to get the spring fully out of the ring before I let go.

Cheers, Al
 

darrahg

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I do the same a Al J (post #5) because I always clean and lube a spring before installation since these main springs are not brand new, hence, old sticky lube is usually on the springs. I hold the T end of the spring into the barrel hole with the butt end of tweezers during installation with a winder.
 

MrRoundel

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It does seem that sometimes the "T" end is a little too big for the hole in the barrel. For this reason I generally pre-fit the "T" into the barrel hole from the bottom. Since I take it for granted that the hole is basically cylindrical, it should fit the same from the bottom as it does through the top.

Not very long ago I was working on a Waltham '77 model that had a nice nickel finish on the barrel and cap. I forgot to pre-fit the "T" and I got caught removing the new alloy spring from the barrel to file the "T" a bit. As I removed it, and the spring was unwinding in my fingers, the last bit shot out like a striking rattlesnake. My flesh survived without a bite, however the "T" smacked the very edge of the barrel and shaved 3mm or so off of the top where the cap set sets into it. What are the odds of that? :mallet: I ended up having to clip off the "hangnail" on the barrel. The cap sets down enough to work, but it's on a nice A.T.&Co. nickel movement, which makes it a bit of an extra snarge. Good luck.
 
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