Sanding Disc Grit Guide for Better Woodworking

A sanding disc that is too coarse can leave scratches which show through a clear finish. One that is too fine can waste time, clog early and fail to remove the marks already there. This sanding disc grit guide woodworking approach is about choosing each abrasive for a specific job, then moving through the grades only as far as the timber and finish require.

For most workshop work, better results come from a sensible grit sequence, a clean disc and effective extraction rather than simply sanding for longer. The aim is to remove the previous scratch pattern evenly, without rounding edges, overheating the surface or filling the air with fine dust.

Sanding disc grit guide for woodworking jobs

Grit numbers describe abrasive particle size. A lower number is coarser and cuts more aggressively; a higher number is finer and leaves a shallower scratch pattern. In the UK, sanding discs are commonly marked with a P-grade, such as P80 or P180. This is the FEPA grading system and provides a reliable reference when comparing professional abrasives.

There is no single sequence for every piece of timber. Freshly machined hardwood, painted furniture, veneered panels and turned bowls all need a different approach. As a working guide, the ranges below cover most random orbital sanding in joinery and furniture making.

| Grit range | Typical woodworking use |
| --- | --- |
| P40-P60 | Removing old coatings, levelling rough sawn timber, heavy shaping and stubborn machining marks |
| P80-P100 | Initial smoothing after machining, flattening filled repairs and preparing timber for finer sanding |
| P120-P150 | General preparation before paint, oil or many wood finishes |
| P180-P240 | Fine preparation for clear finishes, between coats and delicate hardwood work |
| P320 and finer | Denibbing cured coatings, fine finishing and polishing preparation rather than heavy wood removal |

P40 and P60 are removal grades, not general finishing grades. They can save considerable time when stripping paint or bringing rough stock under control, but their deep scratches need proper follow-up. On a cabinet door or a veneered panel, starting at P80 or P100 is often safer unless there is a clear defect to remove.

P120 is the dependable middle ground for a great deal of woodworking. It refines a P80 scratch pattern quickly and leaves timber ready for paint or further finishing. For clear oil, hardwax oil or lacquer on furniture-grade hardwood, P150 or P180 is usually the more appropriate stopping point, subject to the finish manufacturer's advice.

Start with the coarsest grit the job actually needs

The common mistake is beginning too fine because it feels less risky. If planer marks, glue squeeze-out or old finish are still present, P180 will eventually deal with them, but it will take longer and wear out discs unnecessarily. More sanding time also means more chance of uneven pressure, hollowed areas and airborne dust.

Start coarse enough to remove the defect efficiently, but not so coarse that it creates avoidable work. A well-machined solid wood panel might begin at P120. A glued-up tabletop with slight mismatch at the joints may need P80 or P100 first. A painted skirting board being repainted could start at P120 if the coating is sound, or P80 where flaking paint and raised edges must be feathered out.

Veneer deserves more caution. The decorative face can be very thin, particularly on older furniture and factory-made boards. Use a fine starting grit, light pressure and keep the sander moving. It is better to make several controlled passes at P150 than to cut through veneer while chasing one dark mark with P80.

Do not skip too many grits

Each new disc should remove the scratches left by the grade before it. That is why a sequence such as P80, P120, P180 works well for general furniture work. The steps are large enough to be efficient but close enough for the next grit to erase the previous scratch pattern.

Going from P60 straight to P180 often leaves coarse scratches hidden until stain, oil or a low-angle light reveals them. Conversely, moving through every possible grade - P80, P100, P120, P150, P180 - is not automatically better. It can add time without improving the finish if the previous scratches have already been fully removed.

A practical progression for rough solid timber is P80, P120 and P180. For a surface already in good order, P120 followed by P180 may be all that is required. If you are preparing for opaque paint, stopping at P120 or P150 is commonly sufficient. Paint can fill very fine scratches, whereas a clear finish often highlights them.

Check your progress before changing discs. Wipe or vacuum the surface, then inspect it across the grain under a workshop light. The surface should show a consistent scratch pattern with no isolated deeper lines from the previous grit. Pencil guide marks across a broad panel are a simple, reliable way to see whether the sander has worked the whole area evenly.

Match the final grit to the finish, not habit

Sanding timber ever finer is not always an improvement. Some finishes need a little surface texture to bond well, while very fine sanding can burnish dense timber and reduce absorption. This matters particularly with oils and stains.

For paint, P120 to P150 generally gives good adhesion and a smooth appearance. For a clear oil or hardwax oil, P150 to P180 is a sound starting point on most hardwoods and softwoods. P180 to P240 can suit fine furniture, close-grained hardwoods and certain film-forming finishes, but test on an offcut if appearance matters.

Stain is less forgiving. Fine sanding can limit how evenly pigment enters the wood, while inconsistent sanding can make colour take unevenly. Keep the final grit consistent across every visible component, including edges and end grain. End grain absorbs more readily, so it may need a slightly finer grade than the face grain to avoid turning noticeably darker.

For lacquer, varnish and painted coatings, P240 to P320 is normally for denibbing between cured coats, not for the bare timber stage. Sand lightly enough to remove dust nibs and provide a key, without cutting through at corners or edges. A soft interface pad can help a random orbital sander follow gentle contours, but it can also soften crisp details if overused.

Disc choice affects the scratch pattern

Grit is only one part of the result. A quality hook-and-loop disc with an even abrasive coating cuts more predictably and is less likely to shed grains or leave random deep scratches. The backing, hole pattern and pad condition also matter.

Use discs that match the diameter and extraction pattern of your sander. A poorly matched disc may still attach, but restricted airflow reduces dust collection and encourages clogging. Net abrasives are especially useful on dusty timbers, painted surfaces and filler work because extraction can take place across more of the disc rather than only through set holes.

Keep the backing pad in good condition. A damaged or softened pad can create uneven sanding, poor extraction and visible swirl marks. For flat panels, let a random orbital sander sit flat and guide it with light, steady movement. Pressing down does not make the abrasive cut better. It increases heat, loads the disc and can leave pigtails that only become obvious after finishing.

Dust extraction is part of finish quality as well as workshop safety. Dust trapped under a disc can score timber, while a loaded abrasive runs hot and loses its cutting edge. Connecting the sander to suitable extraction, emptying the extractor before airflow drops and cleaning the surface between grits all help the disc work as intended. More efficient, less dust is not just a tidy-workshop claim - it is a practical route to fewer sanding defects.

Know when to replace the disc

Change a disc when it stops cutting cleanly, looks loaded with resin or finish, or starts requiring extra pressure. Continuing with a worn disc produces heat and inconsistent results, often at the point where the job needs the most control. Resinous softwood, paint and some fillers can clog an abrasive quickly, so choose a coating designed to resist loading where possible.

Do not use one disc for every stage simply because it still has some life left. A P80 disc kept for rough preparation is useful, but it should not find its way back onto final finishing work where a stray coarse particle can spoil the surface. Store abrasives dry, flat and away from workshop contamination so the hook-and-loop backing and abrasive face remain in usable condition.

A good sanding sequence should feel controlled rather than complicated. Choose the starting grit by the defect, remove each scratch pattern fully, stop at a grit that suits the finish, and keep extraction working. If a particular timber, coating or sander combination is causing problems, CXS Tools can help narrow down the disc, grade and dust-control setup before more time is spent sanding the same surface twice.