To wind a mainspring with a Bergeon winder, choose a drum slightly smaller than the barrel, hook the arbor into the inner coil, wind the spring smoothly into the drum, align it with the barrel, and release it using the plunger. When done correctly, the spring sits flat, delivers steady power, and protects the entire movement.
If you’re new to watch repair, winding a mainspring looks tricky. But with the right tools and a steady hand, it becomes a simple, almost calming part of the job (we promise — after a few practice runs, it suddenly “clicks”).
In this guide, we’ll walk you through the exact steps with Bergeon mainspring winders, explain why proper technique matters, show common mistakes, and give you practical examples based on real-world watch servicing.
A watch mainspring is a thin, coiled metal strip that stores energy inside the barrel of a mechanical watch. When it unwinds, it powers the gears, escapement, and balance wheel.
Think of it like a tiny metal “battery.” Modern Nivaflex-type springs stay elastic for years, while older blue-steel springs often become “set,” losing power over time. If you’ve opened a vintage pocket watch before, you’ve probably seen those springs sitting almost flat — that’s a classic sign of fatigue.
A healthy, properly installed mainspring delivers even torque and keeps time stable.
A mainspring must be wound correctly to sit flat in the barrel and deliver smooth, consistent power to the movement.
Proper winding ensures:
A quick example:
We’ve seen movements that ran perfectly for the first 20 minutes, then stopped completely — all because the spring was sitting at a slight diagonal inside the barrel.
That’s why this process matters.
Bergeon mainspring winders are precision tools used to safely wind, remove, and insert mainsprings. They’re made in Switzerland and trusted by professional watchmakers worldwide because the machining tolerances are tight and smooth. That smoothness really matters — especially with thin automatic springs that kink easily.
A standard set includes:
Compared with cheaper winders, Bergeon drums stay centered and feed the spring evenly. Many budget winders scrape or grab the first coil, which can ruin a brand-new spring in seconds.
Before jumping into the step-by-step process, make sure you have the right tools on your bench. Here’s a quick checklist:
A small warning here: touching a mainspring with bare fingers can leave natural oils on the surface, causing amplitude loss once the movement runs.
If you need watchmaker-grade tools without the Swiss price tag, SoflyPart offers reliable, Bergeon-compatible options for barrels, winders, lubricators, and movement tools.
Check whether the spring is left-handed or right-handed. Look for bends, rust, or scratches. If you see a kink — even a small one — replace it.
A tiny bend near the outer coil can make the barrel “thump” every rotation.
Lightly lubricate the spring so it winds smoothly.
Pick a drum slightly smaller than the inner diameter of the barrel.
If the drum is too big, the spring will slip while winding.
If it’s too small, the spring twists or jams.
A difference of even 0.2mm can change how cleanly the spring enters the drum.
Hold the outer end with tweezers and place the inner coil inside the drum.
Take your time here — this is where beginners often push the spring too deep before engaging the arbor (we’ve all done it once).
Insert the arbor into the drum and rotate gently until it catches.
Give a tiny upward pull to ensure it’s hooked securely.
If it slips, reset your grip and try again.
Turn the handle with slow, even pressure.
The spring should flow in smoothly without scraping.
A well-aligned spring usually winds in under 5 seconds.
If you feel sudden resistance, stop immediately — resistance is always a warning.
Pull the arbor out slightly and position the drum over the barrel opening.
Match the direction of the spring with the barrel hook.
This part feels delicate, but it gets easier with practice.
Press the plunger gently using pegwood or your thumb.
The spring should slide in cleanly.
When it seats correctly, you’ll usually hear a soft click.
If the spring enters at an angle, the watch may lose 60–90° of amplitude once running. Always check alignment.
Lift the drum straight up.
Check whether:
If something looks off, remove it and repeat the process.
Here are a few tips that make a big difference:
We’ve helped a lot of new hobbyists, and almost all of them needed 3–5 practice sessions before everything started feeling natural.
Professionals feel misalignment instantly. Beginners usually notice only when the spring refuses to release smoothly — or when the watch suddenly stops.
Choose a drum slightly smaller than the barrel’s inner diameter. If the spring resists or feels too loose, switch to the next size.
No. Old or damaged springs can break inside the barrel and damage the movement.
Yes. Cheaper winders often have poorly machined drums that scratch or deform the mainspring. Bergeon is more accurate, smoother, and safer for the movement.
It won’t catch the arbor hook in the barrel and may distort during insertion. Always confirm the direction first.
Beginners usually get comfortable after 3–5 practice sessions.
Winding a mainspring is one of those watchmaking tasks that looks complicated until you actually try it. Once you learn how to choose the right drum, feel the arbor engagement, and release the spring smoothly, the whole process becomes intuitive.
If you’re gathering tools for your repair bench — or replacing your old setup — SoflyPart carries reliable, watchmaker-grade winders, barrels, lubricators, and movement tools that make winding safer and easier.
Take your time, practice with an old spring first, and you’ll be installing new mainsprings with confidence before you know it.