A spinning top is the only machine that proves its own tolerances.
Everything about how it was made is legible in how long it stands. A tenth of a gram out of balance and it walks off the plate inside a minute. A tip ground a fraction proud of centre and it never settles at all.
So we make one. Turned from a single billet of 17-4 PH stainless, hardened, ground, and then corrected on the balancer until deviation falls below 0.8 micron — roughly a hundredth the width of a hair. The tip is polished tungsten carbide, radiused to 0.35 mm, riding a concave sapphire plate.
It spins for eleven minutes and forty-two seconds. That number is not a marketing figure. It is the certified mean of the last hundred pieces, and every one ships with its own recorded time.
| Material | 17-4 PH stainless, condition H900 |
| Mass | 214.0 g ± 0.5 |
| Diameter | 52.00 mm |
| Height | 61.40 mm |
| Tip | Tungsten carbide, R0.35 mm, polished |
| Balance deviation | < 0.8 µm |
| Surface | Bead-blast body, hand-polished crown |
| Plate | Concave sapphire, 90 mm, in a walnut case |
| Certified spin | 11 min 42 s (mean, n = 100) |
| Edition | 100 pieces per year, numbered |
The billet is turned between centres in a single setup, so the body and the tip seat share one axis. Nothing is re-chucked.
Age-hardened at 480 °C for four hours, then air-cooled. The part grows by a few microns and every later operation assumes it.
The tip bore and the crown seat are ground, not cut. This is the operation that decides whether the object will stand.
Spun, measured, corrected by removing material from the underside of the flywheel. Repeated until deviation falls under a micron.
Bead-blast to an even matte, then the crown is polished by hand against a felt wheel. Twenty minutes, one person.
Spun three times on the sapphire plate and timed. The mean is engraved on the underside with the edition number.