Cornish Rolls

A pair of heavy iron rollers, geared to turn inwards against each other, between which ore was crushed. Ore fed from a hopper above passed through the gap and came out reduced to a coarse gravel; a weighted arm held the rolls at the right pressure and let them spring apart on anything too hard to break.

Historical usage

Crushing rolls were introduced to Cornish and Devon copper dressing in the early nineteenth century, John Taylor's installation at Wheal Friendship in 1796 being among the first. They became standard equipment on copper dressing floors and were used at metal mines well beyond Cornwall — the manganese mine at the Lecht in the Grampians crushed its ore between a pair of Cornish rolls driven by a waterwheel almost eight metres across, then re-crushed anything still too coarse before washing and drying it.

How it worked

Two cylindrical rolls are mounted on parallel horizontal axles and geared to counter-rotate, drawing material down into the nip between them. One bearing is fixed and the other held against a weighted lever or spring, so that the gap can open if an unbreakable lump goes through instead of wrecking the machine. Setting the gap sets the product size. Rolls crush by pressure between two surfaces rather than by impact, so what comes out is comparatively uniform, and material fine enough already passes straight through untouched.

Why it was used

The point of rolls is what they do not do. Stamps crush by dropping weighted heads, and on a soft, brittle mineral they overshoot — producing too much fine slime that then escapes the dressing floor with the wastewater. Copper ore in particular breaks down too readily under stamps, so a great deal of value was lost that way. Rolls reduce the ore to the size actually wanted and no further, which is why they took over copper crushing while stamps stayed in use for tin and for low-grade or otherwise difficult ores.

Risks & limitations

Rolls have limited capacity and only a modest reduction ratio, so they suit intermediate crushing rather than either the first breaking of run-of-mine rock or the final fine grinding. The roll surfaces wear and have to be re-dressed or replaced. Like all unguarded nineteenth-century mill machinery, an in-running nip between two powered rollers at waist height on a crowded dressing floor was a serious hazard to the people feeding it.

Regional variation

Called 'Cornish rolls' or simply 'the rolls' in south-west England, and 'crushing rolls' or 'roll crushers' in general engineering usage. A separate building housing them at a mine is a crusher house.

Related terminology

Buddle, Copper, Dressing Floor, Jigger, Stamps, Waterwheel

Mines associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis — not every mine where this might plausibly apply.

• Cwm Elan Mine — Powys (well documented example)
  The 1873 mill was fitted with crushing rolls alongside a Blake's stonebreaker, round buddles and a battery of Collom's patent jiggers — rolls doing the intermediate crushing between the stonebreaker and the separating plant, which is exactly the place they occupy in a dressing sequence.
• Lecht Mine — Moray (well documented example)
  Automatically linked by scripts/link_terms.py: exact-phrase match in the record's own recorded text.

Sources

1. (primary) A Cornish mining glossary — Cornish Mining World Heritage Site — Cornish Mining World Heritage Site
2. (primary) Dressing the Ore — Cornish Mining World Heritage Site — Cornish Mining World Heritage Site

Record created: 25 August 2026 · Last researched: 25 August 2026