Grit of abrasive media question

[Brad Freese]

Harbor Freight sells 3 kinds of abrasive media (the kind of stuff used in blasting cabinets and rock tumblers) and gives their grits as 80, 70 and 24.

When I consult Google, it says Walnut shells are generally useful for final polishes, but these Walnut shells have the lowest grit number.

What gives? Wouldn’t higher grit numbers be better for polishing? Are these just particularly rough walnut shells?

[Kirk Nelson]

My guess is because the walnut shells are softer they would give a smother finish.

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[Caroline Longnecker]

I believe grit refers to media size, not abrasiveness/hardness. Most sandpaper is the same media bonded to the paper, so the grit size is important for informing how much material will be removed and the size of scratches created.

In the context of blasting, grit size is important for filtering and cabinet type, but since the blasting media is more/less abrasive/hard, 24 grit walnut is less abrasive than aluminum oxide or glass.

On Thu, Sep 11, 2025, 17:31 Brad Freese <bradley...@gmail.com> wrote: