40 vs 80 Grit Sanding Discs: Which One Should You Buy?

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Below: what the grit numbers mean, the 40 grit discs in the listings, how to match a disc to a sander, and answers to common grit questions.

40 vs 80 grit sanding discs: what the grit number means

A lower grit number means a coarser abrasive, and a higher grit number means a finer abrasive. The POTUINOM listings group 40-100 grit as coarse grit for rough processing, and list 120-320 grit for conventional polishing and 400-2000 grit for grit polishing. That puts 40 grit and 80 grit inside the coarse band, with 40 grit at the coarse end and 80 grit finer within the same band.

For garage work, that difference shows up in the cut. A coarser disc takes material off faster on heavy stock, rust and old coating, and a finer disc takes material off more slowly and leaves a smoother surface for the next stage.

Hole patterns and dust collection also shape the choice. Discs with holes line up with a sander pad so dust can move away from the surface, and the listings describe dust removal as a way to keep the workspace cleaner.

The 40 grit discs in the listings, in ranked order

The listings in this guide are all 40 grit discs, so the ranking below compares 40 grit options, and the grit discussion above covers where 80 grit fits as a finer step.

Serious Grit 6-Inch 49-Hole P40 Grit Sanding Discs. The listing states 6-inch, 49-hole, 40 grit hook and loop sanding discs in a 25 pack, compatible with Festool 150 Series ETS and Rotex random orbital sanders with 6 inch pads. The listing describes polyester film construction with a 60% nylon hook and loop backing, a zinc stearate anti-clog coating, and wet and dry use for wood, metal, drywall, epoxy and painted surfaces, including auto body work, paint removal and wet sanding. The film construction and anti-clog coating put this disc at the top of the ranking for finish quality on a compatible sander, with the limit that the stated fit is for Festool 150 Series sanders, so pad fit must be checked before ordering.

EZARC Zirconia Flap Discs 40 Grit. The listing states a 4-1/2-inch diameter flap disc with a 7/8-inch arbor size, Type 29, in a 12 pack, with 90 abrasive flaps of blue zirconia oxide grains. The listing states a maximum 13,300 RPM grinding speed and a working angle of 15 to 20 degrees for edge and corner grinding and work on welded seams. The listing states uses for metal or wood, for removing weld reinforcement, deburring, polishing and rust removal. A flap disc suits an angle grinder rather than an orbital sander, so this pick ranks for metal work and weld cleanup.

POTUINOM 100PCS 5 Inch Sanding Discs 40 Grit. The listing states 100 pcs of 5 inch, 8 hole, 40 grit hook and loop sanding discs for random orbital sanders. The listing states aluminum oxide abrasives, a thickened hook and loop back, and uses for grinding, polishing and derusting of metal, non-metal, wood, rubber, leather, plastic, stone and glass. The listing also states suitability for most 5-inch random orbital sanders. The large pack size and broad stated uses make this disc a practical coarse option for general garage sanding, ranked below the film disc and the flap disc on stated construction and on the angle grinding uses the flap disc covers.

POTUINOM 100PCS 6 Inch Sanding Discs 40 Grit. The listing states 100 pcs of 6 inch, 6 hole, 40 grit hook and loop sanding discs for orbital sanders, with aluminum oxide abrasives and a thickened hook and loop back. The listing states the same broad uses as the 5 inch version, for grinding, polishing and derusting of metal, non-metal, wood, rubber, leather, plastic, stone and glass. This listing carries a contradiction: the title and bullets state 6 inch, while the spec table lists 5.0 inches. Trust the title and bullets over the spec table, and treat this disc as a 6 inch disc, checking pad size before ordering. The contradiction puts this disc last in the ranking, even though the stated pack size and uses match the 5 inch version.

How to choose between 40 grit and 80 grit for a garage job

1. Start with the surface. Heavy stock removal, rust and weld cleanup call for 40 grit, while a surface that is already close to shape calls for 80 grit as a finer pass.
2. Match disc size to the sander pad. A disc smaller than the pad leaves pad exposed, and a disc larger than the pad overhangs the edge, and a flap disc needs an angle grinder rather than an orbital sander pad.
3. Match the backing and fit. Hook and loop discs need a matching hook and loop pad, and a flap disc needs the arbor size stated for that disc.
4. Match the hole pattern to the pad. Holes that line up with the pad let dust move away from the surface, while holes that do not line up leave dust in the way.
5. Check the maximum speed stated for the disc. A disc used above its stated maximum speed is the wrong disc for that grinder, whatever the grit.
6. Work in stages. Move from a coarse disc to a finer grit before finishing, rather than trying to finish a rough surface with a coarse disc alone.
7. Plan for dust. Use dust collection where the sander supports it, and keep the workspace clear while sanding.

40 vs 80 grit sanding discs for paint and body work

Paint and body work shows the grit choice clearly. A coarse 40 grit disc suits paint removal and heavy shaping, where material needs to come off fast, and a finer 80 grit step suits work after the heavy removal, where the surface needs smoothing before the next stage.

Metal work follows a similar pattern. A flap disc suits weld seams, edges and corners, where the angle of the disc does the work, while a flat orbital disc suits broad surfaces that need even sanding. Wood work follows the same logic: a coarse disc shapes and strips, and a finer disc smooths.

FAQ: garage tools

Should 80 grit be used after 40 grit?

Yes, 80 grit works as a finer step after 40 grit, since 80 grit sits finer within the same coarse band the POTUINOM listings describe. The finer step removes less per pass and leaves a smoother surface for the next stage.

Can 40 grit discs remove paint?

Yes, the Serious Grit listing states paint removal and wet sanding uses for its 40 grit discs, including auto body work. Paint removal suits a coarse disc, and a finer grit step after removal suits smoothing the surface before the next stage.

Do all sanding discs fit all orbital sanders?

No, pad size, hole pattern and backing must match the sander. A hook and loop disc needs a matching hook and loop pad, and a disc listed for a stated sander series should be checked against that series, so the pad size and hole pattern must be checked before ordering.

What is a Type 29 flap disc for?

A Type 29 flap disc is a bevel flap disc for an angle grinder, and the EZARC listing states a working angle of 15 to 20 degrees for edge and corner grinding and work on welded seams. The listing states uses for metal or wood, for removing weld reinforcement, deburring, polishing and rust removal.

Why does a listing show different sizes for the same disc?

A listing can disagree with itself, and the POTUINOM 6 inch listing does: the title and bullets state 6 inch, while the spec table lists 5.0 inches. Trust the title and bullets over the spec table, and check the pad size before ordering, since the spec table figure does not match the stated disc size.

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