# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Dc1SN9jRoan
- **Gondola URL:** https://gondola.cc/posts/70003063-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/9152f08b91.jpg
- **Posted:** 2026-09-03T16:54:40.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

A ball bearing works because it is round. Not approximately round. An ABMA Grade 3 ball deviates from a perfect sphere by no more than 0.08 micrometres, roughly one seventh of the wavelength of green light.

Most rolling elements begin as AISI 52100 through-hardening chrome steel: one percent carbon, one and a half percent chromium, vacuum degassed until dissolved oxygen falls below 10 parts per million. Oxide inclusions are the enemy. A single alumina particle 20 micrometres across becomes a stress raiser under repeated Hertzian loading, and the fatigue crack initiates there rather than at the surface. Cleaner steel lifted bearing fatigue life by roughly an order of magnitude between the 1960s and today, with no change to the geometry at all.

The forming sequence:

- Wire is sheared into slugs and cold headed between hemispherical dies, producing a rough ball girdled by a flash ring
- Flashing removes that ring between a rotating grooved cast iron rill plate and a stationary one
- Soft grinding brings the ball within roughly 40 micrometres of finished size
- Austenitising near 840 degrees Celsius, oil quenching, then tempering around 160 degrees Celsius produces martensite at 60 to 64 HRC
- Hard grinding followed by hours of lapping in abrasive slurry removes the final few micrometres

Rings follow their own path: turned from tube stock, hardened, then ground and superfinished with an oscillating abrasive stone to a raceway roughness near 0.02 micrometres.

Assembly usually relies on the Conrad method. The inner ring is pushed hard against one side of the outer ring, opening a crescent gap, balls are dropped through, the rings are recentred, the balls spaced evenly, and the cage set in place.

Finished sets are then sorted by measured internal clearance in increments of a few micrometres.

Precision is not the final step of the process. It is the product.

#stemantics #engineering #manufacturing #materialsscience #precisionmachining

## Stats

- **Views:** 21,819
- **Likes:** 103
- **Shares:** 0
- **Comments:** 1

## Tags

engineering, materialsscience, precisionmachining, manufacturing, stemantics

---
Copyright (c) Gondola