JPK Watches

Notes from the bench

Workshop

Working notes rather than tutorials. I'm learning this, not teaching it — if something here contradicts an actual watchmaker, believe the watchmaker.

Entry 07 · Regulating

Regulating an NH35 without a timegrapher

A proper timing machine is a few hundred dollars. A phone, a quiet room and a free acoustic app will get a healthy NH35 inside ±10 seconds a day, which is well past the movement's own spec.

The method: rest the watch crown-down on a hard surface with the phone mic right against the case, let the app settle for a full minute, then nudge the regulator arm in very small increments — smaller than you think, the arm has a lot of authority. Check in all six positions if you're being thorough, or just crown-down and dial-up if you're being realistic.

Where it stops working: a phone mic tells you rate, roughly. It won't reliably tell you beat error or amplitude, and those are the numbers that reveal a movement actually needs service rather than adjustment. If the rate won't hold steady across positions, the problem isn't the regulator.

Entry 06 · Lesson learned

The case back I ruined in four seconds

Three-prong case back openers work right up until they don't. Mine slipped under load on a tight back and dragged a prong across the brushed finish in a single arc. Four seconds, permanent, and entirely my fault for using a tool that has nothing holding it in place.

Replaced it with a Jaxa-style wrench that screws down over the back so the bits can't climb out. It costs about ten dollars more and I should have started there. The scarred case back is still on the watch as a reminder.

Entry 05 · Buying

Reading a marketplace listing properly

Listing text on DHgate and AliExpress is copy-pasted between sellers constantly, so the description is close to worthless as a spec sheet. What I actually rely on:

  • Photos of the real item, not renders — look for the same lighting and background across the gallery.
  • The Q&A section, where other buyers have already asked the measurement questions.
  • A direct message before ordering. "What is the crystal seat diameter in mm?" A good seller answers in a sentence.
  • Reviews with photos, filtered to the lowest ratings first. That's where fit problems surface.

None of this is foolproof. Budget for one wrong part per build and it stops being annoying.

Entry 04 · Technique

Matching lume, and why mismatches haunt you

C3 lume is green in daylight and glows green. BGW9 looks white and glows blue. Mixing a C3 dial with BGW9 hands looks completely fine at your desk and looks obviously wrong the first time you check the watch in a dark room.

Buy dial and hands from the same seller, in the same order, with the lume type stated. It's the cheapest problem on this whole page to avoid and the most irritating one to live with.

Entry 03 · Technique

Dust is the actual enemy

Every build I've done has had at least one dust particle end up under the crystal, and every time it was visible only after the crystal was pressed. Things that measurably helped:

  • Work in a bathroom after running a hot shower — the steam pulls dust out of the air.
  • Rodico on a toothpick lifts particles that a blower just relocates.
  • Press the crystal last, inspect at a low angle under bright light immediately before.
  • Accept that you'll open it again. Plan the gasket for two openings, not one.

Entry 02 · Getting started

What I'd buy first, in order

If someone handed me $60 and asked what to buy before their first build, in this order: a movement holder, a hand setting set with a blower, Rodico, a spring bar tool, and a loupe. The crystal press and case wrench can wait until the first build that needs them.

Everything in that list is on the parts & tools page with notes on which cheap versions are fine.

Entry 01 · Beginning

Why I started taking watches apart

A dead quartz watch of my grandfather's that no shop wanted to touch because the parts hadn't been made in thirty years. I didn't fix it — it's still in a drawer — but opening it up was the first time I'd seen the inside of a watch, and that was that.

The mechanical stuff came later, and the parts-sourcing rabbit hole after that. It turns out you can assemble a watch you'd genuinely wear for less than the cost of a night out, if you're willing to lose a few evenings to it.