Two families of round metallic abrasive, with different prices and different behaviour. The choice is not obvious, and in shot peening it matters more than in blasting.

How they are made

Cast shot is produced by atomising molten steel. The droplets solidify into spheres.

Cut wire is produced from drawn wire, cut into cylinders with length equal to diameter. The cylinders are then rounded in a conditioning process.

The manufacturing difference explains everything else.

Consistency

Cut wire starts from drawn material with a uniform structure. Every particle has practically the same hardness and the same mass.

Cast shot can contain internal irregularities left from solidification. Across a batch, properties vary more from particle to particle.

Wear behaviour

This is the most visible practical difference.

Cut wire wears by gradual reduction in size while keeping its shape. It does not fragment. Its service life in the circuit is considerably longer.

Low carbon cast shot also wears by gradual reduction, losing its round shape as it gets smaller.

Angular grit, for comparison, wears rapidly and is consumed noticeably faster.

What it means for cost

Cut wire costs more per kilogram. It lasts more cycles, and consumption per part can be lower.

The correct comparison is not price per kilogram. It is cost per part processed, which includes both consumption and machine wear.

When it really matters

In cleaning applications, where oxide removal and a uniform appearance are required, cast shot covers most cases.

In shot peening, consistency becomes critical. The effect depends on the energy of each particle, and variation translates directly into intensity variation. Here cut wire earns its price.

The practical rule

If the result is assessed visually, choose on cost per part.

If the result is measured and documented, choose on consistency.

Aluminium needs a different medium

Here the rule changes completely. Aluminium is not peened with steel shot unless you accept ferrous contamination in the surface.

Iron particles left in the surface layer form galvanic couples with the aluminium. The result shows up later: staining, pitting, sometimes precisely in the areas you meant to protect.

What is used instead: stainless steel cut wire, ceramic media or glass beads, depending on the required intensity and how fine the surface has to be.

If process reasons make ferrous media unavoidable, peening does not end at the machine: a decontamination step follows, and it belongs in the specification rather than being optional.

On aluminium the question is not “what gives me the required intensity” but “what does it leave in the surface”.

Hardness and as-delivered condition

Cut wire does not come in a single form. It is supplied as cut, with square edges, or conditioned — tumbled until the corners round off. Heat-treated grades exist as well, for higher hardness.

The difference matters in two places:

The edges. As-cut wire has corners that mark the surface. For cosmetic peening or on visible parts, conditioned media is used.
The hardness. Media softer than the part deforms instead of transferring energy. On hardened parts you will not reach the required intensity no matter how far you raise wheel speed.

The practical rule: choose media hardness at least at the level of the part. Below that you lose intensity and waste media. Far above it, you pay more and wear the liners faster.

Cut wire or cast shot: choosing the abrasive