# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DaO3QPkAzvk
- **Gondola URL:** https://gondola.cc/posts/67391861-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/1825c4f2ab.jpg
- **Posted:** 2026-07-01T01:43:42.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Most cutting tools shape a part over many passes. A broach does it in one stroke, because it carries its own depth of cut built into the tool.

A broach is a tapered bar studded with rows of teeth, each standing slightly proud of the last. That step is the rise per tooth (RPT), and it is the whole trick: as the broach is pushed or pulled through the workpiece in a single linear pass, every tooth peels away a fresh layer roughly equal to its rise above its neighbour. The tool never cuts deeper by feeding, the depth is machined into the geometry itself.

The teeth are graded across three zones:

- Roughing teeth, largest RPT (0.05 to 0.15 mm), doing the bulk removal
- Semi-finishing teeth, tapering the increment down
- Finishing teeth, all sat at identical height with zero rise, sizing the profile and absorbing tool wear as the front teeth dull

Between the edges sit gullets, the curved chip pockets. A chip has nowhere to escape until the stroke ends, so the gullet must swallow the entire curl. Get the ratio wrong and the chip packs solid, spikes the force, and snaps a tooth. The classic rule of thumb ties tooth pitch to workpiece length so only a sensible number of teeth engage at once, keeping the total load survivable.

This is why broaching earns its keep on splines, keyways, internal hexagons, rifling, and the fir-tree roots that lock turbine blades into their discs, geometry too awkward for a single-point tool and wanted in the millions. Speeds are slow, often just a few metres per minute, yet the broach roughs and finishes in the same second at surfaces down to 0.4 µm Ra. It is brutally expensive and cuts one form only, which is precisely why it lives in high-volume production.

One stroke, one part, and the whole toolpath forged into steel.

#stemantics #machining #manufacturingengineering #metalworking #mechanicalengineering

## Stats

- **Views:** 0
- **Likes:** 1,336
- **Shares:** 0
- **Comments:** 13

## Tags

manufacturingengineering, metalworking, machining, mechanicalengineering, stemantics

---
Copyright (c) Gondola