# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Dd1m9nzAOTX
- **Gondola URL:** https://gondola.cc/posts/71131441-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/d4e0ac2737.jpg
- **Posted:** 2026-09-28T16:25:47.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

A hydraulic metal shear does not really cut steel. It fractures it, along a line controlled to within a fraction of a millimetre.

The cycle begins when a row of hydraulic hold-downs clamps the sheet against the lower blade. Twin cylinders then drive the upper blade downward, and the material passes through three distinct phases:

- Rollover, where the blade indents the surface and the edge deforms plastically before any separation occurs
- Burnish zone, where the metal flows in pure shear and leaves a smooth, polished band, often around one third of the thickness
- Fracture zone, where cracks initiate at both blade edges, propagate through the section and meet, leaving a rough, granular face

Whether those cracks meet cleanly depends mostly on blade clearance. For mild steel, typical practice sets the gap at roughly 5 to 10 percent of sheet thickness. Too tight and secondary shearing appears, doubling the burnish band and accelerating blade wear. Too loose and the sheet is dragged into the gap, producing heavy burrs and a distorted edge.

Rake angle is the second critical variable. Inclining the upper blade, commonly between 0.5 and 2.5 degrees, makes the cut progress along the sheet like a pair of scissors rather than loading the full length at once. Required force falls dramatically, at the cost of some bow and twist in narrow strips.

Hydraulics made this scale of force practical. Joseph Bramah patented the hydraulic press in 1795, applying Pascal’s principle that pressure in a confined fluid acts equally in every direction. A pump running at a few hundred bar, acting on large bore cylinders, delivers hundreds of tonnes, while a relief valve ensures the machine cannot overload itself on oversized stock.

Modern CNC shears add servo-driven backgauges repeatable to around 0.1 mm and automatic clearance adjustment keyed to material grade and thickness.

A clean edge is not cut. It is a managed fracture.

#stemantics #manufacturing #metalworking #engineering #materialsscience

## Stats

- **Views:** 12,729
- **Likes:** 52
- **Shares:** 0
- **Comments:** 1

## Tags

metalworking, engineering, materialsscience, manufacturing, stemantics

---
Copyright (c) Gondola