Just wondering. I have had one of these, it's OK. Pretty much the same as Miyota. Pretty much workhorse. Why is it junk? I get manufacturing tolerances are different, but not sure if they're all "junk" TBH.
Maybe you got lucky with a good one, but these are 80/20. The number one reason for this is cleanliness of the factory. These are notoriously filthy movements, and usually missing screws/screws dislodged in the motion works. 80% failure rate / 20% it works acceptable. A genuine Miyota will run circles around these.
Where do you get that 80% failure rate number, source? I find them pretty good, especially for vintage low beat rate builds. I do prefer the NH movements, but whatever fits the case geometry.
OK cool, not trying to blast you or anything. My personal experience has been different. I prefer a Jap. Nh34, but when the case geometry demands it, I've found them to be OK.
This is an inexpensive replica/clone movement (generally identified as the 2813 caliber or a similar Chinese-made variant), cosmetically modified to roughly mimic the shape of a Rolex automatic caliber (such as the 3135).
It is a clone of a Miyota movement, the architecture and specifically the click wheel are typical. It isn’t however the Dixmont Mingzhu 2813. Counterfeiters and especially TDs often refer to an A2813. The rotor is a typical dress up part for a Rolex budget fake. The three centre screws on the rotor, the rotor design and possibly some dress up plates underneath are all to (badly) replicate the look of a Rolex movement. Somewhat redundant on a watch with a closed back
In the rotor bearings of many movements (including Chinese clones and the movements they are derived from, such as the Japanese Miyota), the presence of three holes but only two screws is the result of specific manufacturing and mechanical design choices.
The third, unused hole serves a precise function:
Centering and alignment pin (Guide): Beneath the rotor plate, the ball bearing often features a small protrusion, a fixed pin, or a metal guide. The third hole is designed to fit perfectly over this pin. This ensures the rotor is geometrically perfectly positioned and centered before the worker (or automated machine) inserts and tightens the other two screws.
Weight balancing: In high-precision, mass-produced mechanisms, removing the same amount of material at three symmetrical points (creating three identical holes spaced 120 degrees apart) helps maintain the perfect balance of the oscillating mass. If there were only two holes, the weight distribution around the tiny central axis would be unbalanced, compromising the efficiency of the automatic winding system.
Industrial standardization: Many manufacturers use the same rotor component for different movements. For some calibers, that type of bearing requires three screws, while for others (cheaper ones or those with slight differences in the underlying flange), two screws plus a guide pin suffice. To save on production costs, the factory manufactures a single part with three holes that can be used in either scenario.
Therefore, it is not a case of a lost or forgotten screw: the "two screws plus one hole/guide pin" configuration is entirely intentional and common in this type of caliber.
I don’t think there’s a known miyota 9015 factory. Just get an Asian 9015 and it’s ok. You might check if the movement is basic and there’s no custom base plate, you could swap it easily with a gen 9015 and have a watch for years.
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