Taking apart a watch is easy; putting it back together, however . . .

Taking apart a watch is not difficult. You need the right tools: a magnifying eyepiece and pointed tweezers, to see and handle screws the size of mustard seeds and springs as big as eyelashes. To turn those tiny screws, three jeweler’s screwdrivers. Plus a pointer to nudge parts into place, and an elevated tabletop, to lean your elbows on, to get your face close to your work. Don’t forget to slip on pink rubber finger cots, to keep the oils from your fingertips from corroding delicate parts.

There is one more tool whose purpose doesn’t immediately reveal itself: a round metal tray with ten compartments.

To understand the role of the tray, you need to know what you are doing or, barring that, have the guidance of someone who does, such as Steve Eagle, director of education at the Horological Society of New York. A few Sundays back, Eagle led seven novices through the removal and return of most of the 78 gears, wheels and springs of a Unitas ETA 6497 watch movement.

“Welcome to Horology 101 to 103,” said Eagle. “You’re in for an intense four hours of watchmaking.”

The survival of the mechanical watch half a century into the era of quartz watches — the 50th anniversary of Seiko introducing the Astron is this Christmas — is a miracle of savvy marketing.

“We’ve seen this resurgence in the last 15 years where people are circling back and starting to appreciate the longevity of mechanical watches,” said Eagle. “The artistry behind them, the history, these little miracles that will work under their own power. Such an analog product in such a digital world.”

The classes started in New York in 2015. Those who paid — they waived me in — put out $500. That could buy a starter mechanical watch. Why pay $500 to take a watch apart?

“I took the class to gain a better understanding about how watches work,” said Dr. Adam Cifu, a professor at the University of Chicago Pritzker School of Medicine. “I’ve been collecting for a while but never felt like I had a good enough handle about what goes on inside.”

Before a watch can be disassembled, it has to be stopped. The movements in front of us were running. (“That’s my proof it’s working before you touch it,” Eagle said). That was done by disengaging the beak of the click from the ratchet wheel teeth, to give an idea of the blizzard of terms that would fall upon the class. By releasing the tension on the mainspring.

“With all the energy released, and the movement stopped, that means our anesthesia has kicked in, and it is safe to begin our surgery,” Eagle said. “First thing we are going to do is remove the most delicate and the most expensive part of the whole movement: the balance and hairspring.”

One by one, screws came off, and were dropped in the tray. Joined by wheels — train, ratchet and center. The yoke spring, being careful to not let it leap, irretrievable, into the greater world beyond our watchmaker’s tabletop.

The class was held at Oak & Oscar, a watch brand founded by Chase Fancher in 2015.

“Social media is a major part of love for watches,” Fancher said. Particularly Instagram. Instead of selfies, fans take “wristies” — shots of their watches — and will mass together the watches they’ve brought to show off at gatherings in what has been dubbed a “sex pile.”

“Everyone just lays out their watches, 100 watches in one pile,” Fancher said. “Everyone says, ‘Look at that sex pile.’ And then everyone takes a photo. It’s become its own thing.”

I would never suggest that life lessons are hidden within watchmaking. Though some instructions seemed useful beyond merely handling tiny gears.

“If you’re pulling at something and it’s not coming out, the answer to your problem is not more force … You need to re-address your technique,” Eagle said.

“Small little details — they all matter.”

The final hairspring that started it all took some coaxing to get back into place. Eagle went around, helping people. The little gear did not want to sit right, and took a few tries. Then it went from not working to suddenly working, and the watch sprang to life. A surprisingly satisfying process, to spend four hours returning to where you had begun. Eagle said an experienced watchmaker could do it in 10 minutes.