Most abrasive waste isn't caused by cheap product. It's caused by starting at the wrong grit.

Start too coarse and you put scratches into the part that take three more steps to remove — steps that cost you discs, belts, and shop time. Start too fine and the abrasive glazes over, stops cutting, and generates heat instead of chips. Either way you burn money and blame the disc.

This guide gives you the grit number to reach for based on two things you already know: what the part is made of, and what it needs to look like when you're done. Everything else — mineral, backing, pressure — follows from that.

Two Grit Systems. Know Which One You're Reading.

Before any chart is useful, check which scale the number is on. There are two in common use in North American shops, and they stop agreeing exactly where finishing work gets serious.

• CAMI — the North American scale (Coated Abrasives Manufacturers Institute, standardized under ANSI B74.18). Written as a plain number: 80, 120, 320.
• FEPA — the European scale. Written with a P prefix: P80, P120, P320. FEPA grading holds a tighter particle size distribution, which is why it dominates automotive refinish work.

Through the coarse and medium range the two scales track closely. Above roughly 220 they diverge hard, and the gap widens fast. CAMI 400 is not P400 — it's closer to P800. If you assume they're the same in a polishing progression, you will skip two full steps and wonder why the scratches won't come out.

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Three Questions Before You Grab a Disc

Grit selection isn't a preference. It's the answer to a short sequence of questions. Work them in order — each one narrows the next.

1. What's the material?

   Material determines the mineral more than the grit. Carbon steel, stainless, aluminum, and cast iron all fail differently under the same abrasive. Get the mineral wrong and no grit number saves you.

2. How much are you removing?

   A weld bead is stock removal. A scratch is blending. A dull spot is finishing. Estimate the depth of what has to disappear — that sets your starting grit, not your finishing grit.

3. What does "done" look like?

   Ready for paint? A uniform satin grain? Mirror? The required end finish sets your final grit. Everything between the start and the finish is just the progression.

Two numbers, then. Start grit — the coarsest thing that removes the defect. Finish grit — the finest thing the spec requires. The chart below gives you both.

Grit Selection by Material & Finish

Find your material, then your job. Grits are CAMI unless noted. Ranges are starting points for hand and portable power tool work — bench and machine setups may run coarser.

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The Progression Rule: Don't Skip Steps

Every grit does exactly one job: remove the scratches left by the grit before it. That's the whole game. Once you understand it, progression stops being guesswork.

The working rule is never skip more than one step in the sequence. A clean progression looks like this:

Jump from 80 straight to 320 and the 320 spends its life fighting 80-grit trenches. It will get there eventually — after you've burned through three times the discs a 120 and a 180 would have cost, and left ghost scratches that only show up under the coating.

• Change direction every step. Cross-hatch roughly 45–90° from the previous grit. When the old scratch pattern is gone, that step is done. This is the only reliable way to know.
• Don't rush the coarse step. The first grit does the real work. Everything after it is cleanup. Leave a defect at 80 and you'll be back at 80 an hour later.
• Stop when the spec is met. Sanding to 600 for a part that gets powder coated is money set on fire — and the coating will adhere worse.

Non-Woven Grades: A Different Language

Non-woven abrasives — surface conditioning discs, convolute and unitized wheels, hand pads — don't use grit numbers. They use grades: Coarse, Medium, Very Fine, Super Fine, Ultra Fine.

That's not marketing. It reflects how they work. A coated disc presents a rigid layer of mineral at a fixed height. A non-woven abrasive holds mineral in an open, resilient nylon web that conforms to the part and flexes under load. Same nominal particle, very different scratch.

↔ Scroll table horizontally on mobile · Equivalents are approximate

Grade names are broadly consistent across the industry. Color coding is not — every manufacturer uses its own. Read the grade, not the color.

Mineral Matters More Than You Think

Grit sets the scratch. Mineral sets whether you get a scratch at all. Four minerals cover essentially all metalworking:

Five Ways Shops Waste Abrasive

• Starting too coarse "to save time." You'll spend that time back, doubled, removing your own scratches.
• Leaning on the tool. Every abrasive has a pressure window. Above it you crush grain and generate heat instead of chips. The disc is engineered to cut — let it.
• Running a loaded disc. A clogged abrasive stops cutting and starts burnishing. It's not saving you money at that point, it's costing you heat damage. Clean it or replace it.
• Wrong RPM. Too slow and you're not cutting. Too fast and you're generating heat. Check the tool's rated speed against the abrasive's max safe speed — and never exceed the abrasive's rating.
• Finishing past the spec. Extra steps that nobody asked for are pure cost. Know the required finish before you start, and stop when you hit it.

Common Questions