How to Choose 5 Inch Sanding Discs: the Right Grit

The short answer on 5 Inch Sanding Discs

The one rule that governs the choice: match the grit to how much you are removing, then pick the disc form to the tool you run it on. Grit controls how much the disc takes off per pass; the form (PSA paper, mesh, or 8-hole hook-and-loop) is set by the tool and the job. Get those two in the right order and everything else follows. The sequence to keep in your head is:

P80 – P120 to remove old finish, primer or stock 🪵
P150 – P180 to level fillers and knock down high spots
P240 to bring the surface to final prep
P320 – P400 to leave a clean, even scratch under the next coat ✅

Two cases where the standard ladder bends. On very slick plastics or a glossy old finish, a coarse grit burns rather than cuts, so start a band finer than the ladder suggests. On soft hardwoods that pack grain easily, holding one grit in one spot clogs the face, so drop to a coarser grit and keep the tool moving, or move to the mesh form. If your job is everyday finishing on a hand orbital or a flap disc holder, P150 to P320 is where the 5-inch disc spends most of its working life, and if the job is really stock removal instead of finishing, a flap disc on the grinder is the right tool. The grit reasoning is the same, and the flap disc range is where to make that call. If the panel is a body panel, the sequence is driven by repair type rather than grit taste, and the automotive repair sanding notes walk it by repair type.

How a 5-inch sanding disc is built, and what the forms trade off

A 5-inch disc is a 127 mm paper-backed abrasive. The 5 Inch Sanding Discs range carries three forms, and they are not three separate products so much as three answers to the same question: how should this disc carry its grit, and what does the tool that spins it need from the disc?

PSA (paper, hook-and-loop backed) — the workhorse. A paper disc carries the grit face and snaps onto a matching hook-and-loop pad on an orbital sander or a PSA holder, and swaps in seconds. Most of the finishing world runs on PSA, and a 5-inch PSA on an orbital is the everyday tool for wood, primed metal and panels.
Mesh — an open web of cut slots instead of solid paper. Dust passes through the face rather than sitting on it, so the disc stays cleaner and the cut stays even on high dust or enclosed work where the tool has dust extraction. The trade is cost and the need for a matching mesh pad, so many shops keep mesh for the dirty jobs and PSA for the clean ones.
Hook-and-loop with cut holes, the 8-hole 5-inch disc — a rigid disc with a hook-and-loop face and eight cut holes, clamped onto a flap disc holder on an angle grinder. This is the compromise: fast, aggressive removal where a flap disc belongs, but at a size that still fits the 5-inch hole of most holders. If your machine is a real grinder doing real stock removal, this is likely the disc to spec, and the 8-hole 5-inch hook-and-loop disc page is where to see what that means for your tool.

The grit number on any of the three is the same kind of number, and that is the point. A P120 on PSA, on mesh or on an 8-hole disc is the same grain size: FEPA, or ISO 848, which is the scale most international buyers quote. The grit is where the job gets done. P60 digs in and leaves deep, visible scratches. P400 and finer leaves a light, even mark that a top coat sits over. On 5-inch discs you will spend most of your time between P80 and P400, because the small disc exists for control, not for stripping. The full range we supply runs P60 to P5000, and the sanding disc range shows where each band sits against the forms we stock. The hook-and-loop sanding discs page is where to see the 3, 4, 5 and 6-inch hook faces side by side if you are standardizing one pad system across a shop.

One more piece of construction that is easy to miss: the grit is not glued on randomly. The grain is embedded in a resin bond at a density the maker calls the charge, and that density decides how long the face cuts before it dulls. A tight, dense charge holds a sharp cut through a long pass; a looser charge stays open on materials that would pack it. The two look identical on the shelf and pull apart on the first panel. That is why the grain and the charge, not just the P-number, belong on the spec sheet when you are comparing two discs that both say P120.

Grain and the P-number: what actually decides the cut

The grit tells you the size of the cut; the grain tells you how the disc gets through it. Most 5-inch stock runs one of three grains, and the pick changes the feel of the job more than people expect when they first spec one.

Aluminium oxide is the default for general work on wood, paint, primer and filler. It is tough, cuts evenly, and is the grain to reach for when you are not chasing speed. It is also the grain that shows up on most PSA paper faces, and its even, forgiving cut is why it is the standard on the 5-inch hook-and-loop lines.
Silicon carbide is the pick for soft, slick or heat-sensitive surfaces: plastics, some composites, glass-fiber and anything where aluminium oxide would burn rather than cut. The grain is sharper and cleans itself better, which is why it suits the fine end of the range.
Ceramic is the premium, longest life option. It is a semi open grain that does not clog, and the value shows up on high volume work where cost per finished surface, not the price per disc, is the number you are managing. It is the grain most OEM and branded runs get built on, because the buyer is paying for a long cut that holds through the whole run.

Backing on a PSA disc is a cloth-grit face bonded to a paper backing, and the disc as a whole carries a hook-and-loop layer that the sander holds with a matching pad. The one thing to confirm before you order is that your tool wants a hook face on the pad or a loop face, because the disc and the pad have to meet in the middle. That is a detail worth a line on the spec sheet, and one to check with sales rather than guess.

The P-number ladder for 5-inch work, with where each band lands:

P80 – P120 — fast removal, old finish, primer knockdown.
P150 – P180 — leveling fillers, knocking down high spots. This is the band that shows up in most enquiries, and the band that decides whether the surface under the top coat is even.
P240 — the bridge to final prep.
P320 – P400 — the last sand before a clear coat or a top coat.
P600 and finer — wet sanding and polishing, where the disc is doing less cutting and more de-raising.

The practical rule: match the grain to the material, then set the grit to the cut. Grain decides how the disc behaves; grit decides how much it removes. Change one deliberately and keep the other fixed, or you are solving two problems at once and you will not learn which one moved.

What the P150 band in 5 Inch Sanding Discs does

Because P150 to P180 come up in so many enquiries, the 150 band is worth treating on its own. Its whole job is to take the peaks off a surface that has just been sanded or filled, without opening deep new scratches, so that the next finer step has a short, even pass instead of a cleanup of deep grooves. That is a different job from P80, which removes, and from P320, which leaves a clean scratch. If a panel goes from P80 straight to P320, the P80 scratches survive under the next coat and show through it. That is the single most common reason a surface looks sanded but not finished, and the fix is the 150 and 180 steps in between.

Where the band earns its keep is on filled surfaces, on primer, and on any surface that will take a clear coat. Where it fails is as a first pass over coarse texture or an old thick finish: a fine-grained face on a coarse job glazes and loads instead of cutting, and the disc feels slow even when the tool is at speed. The second failure is pressure: the band wants a light, moving tool. Pressing into it is the opposite of what the grain wants, and a burned, browned face is the sign that the operator leaned in instead of letting the charge cut.

If you are standardizing one disc on the bench and you must pick a single grit, the P150 band is a better pick than P320 for two reasons. First, it covers both the filler leveling and the high-spot work, which is most of the pass. Second, a step down to P240 or P320 is a short, even pass, while a step up from P80 is a long one. The grit to buy is the one that does the real work, and on most finishing lines that is the P150 band.

A worked sequence: a door, grit by grit

A house door or a small panel is the job that shows every step, because the surface is flat, the finish is visible, and a missed grit shows in the top coat. A sequence that works from bare wood to a ready-for-oil surface:

P80 — cut through whatever old finish is on the wood. This is the removal pass; you are looking for an even, bare surface, and the deep scratches do not matter because every step after this is finer.
P120 — even out the P80 marks and take any high edges down. The scratch direction should start to even out, and the surface should feel uniform under your hand.
P180 — the leveling step on bare wood, doing the same job as the P150 band on filled work. If you are filling, this is where the filler gets brought down and the surface is ready to prepare for the top coat.
P240 — final prep before the first coat. The mark is light and even, and a top coat over it sits without catching the scratch.
P320 — between coats, to open the surface so the next coat bites. Between coats, keep the lightest touch you can: you are breaking the gloss, not removing stock.

The two habits that keep this sequence honest are the grit ladder and the touch. Every step is finer than the last, and the last two steps are where the panel is actually finished, so they get the lightest pressure and the most moving. If the top coat catches the scratch, the step that was missed is the one two bands earlier, and the fix is to go back and re-sand the surface at that grit, not to press harder on a finer one. The automotive repair notes run the same ladder on body panels, where the grit steps differ by repair type and the fill band runs coarser than a house door.

PSA pads: match the hook to the loop, and swap when the face goes

The hook-and-loop system is where a 5-inch disc starts to feel cheap, and where a shop loses money quietly. The pad on the sander is the part everyone assumes, and it is the part that degrades first. A worn hook on the pad does not hold the disc the way a new one does, and the disc shifts, edges lift and the face starts to peel at the rim. The fix is not a new disc; it is a new pad, which costs a fraction of the disc it is protecting.

Hook on the pad, loop on the disc is the setup most orbitals ship with, and the loop is the disc side that wears. The hook on the pad grabs the loop fibres, and the loop on the disc is the wearing part. When the loop face goes dark and matted, the disc is not holding the way it was, and the pad may be the cause, not the disc.
Loop on the pad, hook on the disc is the flip, and it is the setup that keeps a pad cleanest, because the loop face sheds dust instead of trapping it. Where one pad runs all day, the loop-on-pad setup is the one that keeps the disc square.

The one thing to check when you standardize is that every disc on the shelf and every pad on the sander agree on which side is which. A shop with one disc and two pad types will quietly run the mismatched pair, and the disc will not hold, will not square, and will edge-lift, and the operator will blame the disc. A disc that does not square on the pad is not cutting flat, and the panel will show it in the top coat as a low spot the operator cannot find. The hook-and-loop sanding discs page lists the forms by size, and the quotation form is where to confirm the pad pairing before a bulk order ships.

Speed, dust and safety, in plain terms

Tool speed is the hard limit, and it is the number most people under-check. Surface speed is how fast the cutting face of the disc travels per minute, and it rises with the tool's no-load RPM and with the disc diameter. A 5-inch disc is a hand-tool disc: most stock is built for orbital and flap disc holders that run a few thousand RPM, and those numbers need to stay under the disc's rated maximum. Where the disc does not print a number, confirm the rated speed against the model and keep the tool below it.

Orbital sanders and flap disc holders take a hook-and-loop or PSA face and spin the disc to a few thousand RPM. The disc almost always has headroom, which is why the 5-inch on an orbital is the everyday finishing tool.
Angle grinders run 11,000 to 13,000 RPM at the spindle, and that is well past the rating of most 5-inch paper discs. A 5-inch PSA is not a tool to run on an angle grinder; the 8-hole 5-inch disc on a flap disc holder is the compromise, and even there the holder's speed has to clear the disc's rating before you start.

One failure mode is worth naming on its own: a disc used past its rated speed can fail at the face or the rim, and the fragments fly off in an arc from the rim. Keep the tool guard fitted every time, and stay under the printed maximum.

Dust is the other half, and the one that is easy to under-plan on a small disc job. 5-inch sanding throws fine dust that is easy to breathe in, and on wood and on older paints the dust carries its own hazard. The PPE baseline is at OSHA 29 CFR 1910.132, PPE general requirements, the guard requirement is at OSHA 29 CFR 1910.244, portable power tools, and a practical read of the wheel side of the job, including guards, speed and dust, is at CCOHS, Abrasive Wheels. Wear eye and face protection on every pass, match the respiratory protection to the dust load when you cannot keep the extraction at the face, and run dust extraction with the right filter for the material, with the waste in a sealed bin rather than swept to the corner. Under compliant speed, a correct fit and the right PPE, the risk of these tools is reduced, not zero, and that is the honest line to keep on the shop floor.

Grit by material: a quick reference

Material changes the starting grit even when the tool is the same. The list below is the starting point, not a rule, because the finish you are aiming for and the thickness of the stock both shift the sequence in one direction or the other.

Softwood and hardwood 🪵 — P80 to P120 to bare, P180 to P240 to prepare, P320 to P400 to finish. Soft stock packs a disc fast, so a coarser grit and a moving tool beat a fine grit held in one spot.
Primed or filled surfaces 🎯 — P150 to P180 to level the fill, P240 to prepare, P320 to P400 to finish. The fill band is where the sequence earns its keep.
Bare metal and steel ⚙️ — P80 to P120 to open the surface, P150 to P180 to level, P240 to prepare, P320 to P400 for final prep, P600 or finer for polish. Keep the disc dedicated to one metal, because a mild steel job leaves particles in the grain that will show on the next surface.
Plastics and glass-fiber 🔵 — P120 to P240 to prepare, P320 to P600 to finish. Softer and slicker than metal, so a coarse grit burns and the sequence runs finer than the metal one at every step.
Stone and composite 🧱 — P60 to P80 to open the face, then P120 to P240. A rough casting or composite face packs a fine grit, so you work coarse to fine in steps rather than jumping to a fine disc.

The rule underneath the list is always the same: match the grit to the material and the finish, and let the grain decide how the cut feels. Aluminium oxide is the grain to default to on wood and metal, silicon carbide is the pick for slick and soft surfaces, and ceramic is the one for high volume work where the cost per surface is the number you are managing. For the grains we stock against each form, the sanding disc range and the metal fabrication application notes are where to confirm before you order.

The grit standard to write on the purchase order

The grit number is only meaningful when you name the scale, and that is where two suppliers quietly end up shipping you two different discs. FEPA (ISO 848) numbers and the older ANSI numbers do not always line up, so a 150 on one scale is not a 150 on the other, and the surface will show the difference. When you buy 5-inch discs from more than one source, state the scale in every enquiry and ask which one the stock is on; the reference is at the FEPA grit standard.

The practical reason it matters is that a wrong scale gives you the wrong cut. If you think you are buying a P240 to prepare and the supplier is quoting on a coarser ANSI 240, you will arrive at the bench with a grit that removes more than you planned, and the surface under the next coat will carry the deeper scratch. Two moves prevent it: always name the standard (FEPA or ISO 848), and keep the shop to one scale so the grits on the shelves are comparable. For a bulk or branded order, the scale is a field on the spec sheet, not a footnote, which is why it is one of the things the quotation form asks for. The grain and the charge round out the spec: name the grain, name the charge if you are comparing two P-numbers from two makers, and the two discs you receive will cut the same way.

Specing a wholesale or OEM order: the fields

When you move from buying a handful of discs to a wholesale or OEM run, the conversation shifts from grit to a spec sheet. The fields that make or break an order are the ones below, and they are exactly what the OEM service page walks through in more detail.

Grain and grit — the grain (aluminium oxide, silicon carbide, ceramic) and the FEPA or ISO 848 grit, stated on the same scale the shop buys to.
Disc form — PSA, mesh or 8-hole hook-and-loop, chosen for the tool and the job as above.
Pad pairing — hook on the pad or loop on the pad, so the disc and the sander agree on which side is which.
Grit standard — FEPA or ISO 848, written on the order so the stock does not mix scales.
Label and packing — your logo, your part code and any spec sheet you want on the box for a branded run.
Quantity and lead time — the order quantity and how fast it needs to be on the shelf, which sets whether it ships from stock or gets made to your run.

Send those six fields and the order is a conversation instead of a gamble. The quotation form is where to start, and if you are new to a branded run, ask for a sample against the spec before the full order so the grit, the form and the label all match what you expect.

Cost, life and lead time

On cost, people usually buy the cheapest 5-inch disc per unit and then pay for it in surface time. A sharper grain that lasts longer over the same panel can work out cheaper per finished surface than a cheap disc that glazes and gets swapped. For steady volume, cost per surface is the number to manage, and it is the number the quotation form should be built around, because at volume the per-panel cost is where the saving actually lands.

Disc life shows up in two ways. The grit wears down and the face goes dull, which is normal and is the reason you step grits on a long job. Or the backing and edge start to fail, which points to a speed or fit problem rather than a grit problem. If the life is short and the disc feels like it is running hot, the form is probably the wrong choice for the tool speed, and that is a form question, not a grit one. A disc that will not square on the pad is not a life problem, it is a pad problem, and the hook-and-loop sanding discs page is where to check the pairing before you blame the disc.

Lead time splits two ways. In-stock grits and common forms ship fast, and off-grid grits or a branded run take longer because the label, the packing and the spec sheet all have to line up. For a wholesale or OEM order, confirm the minimum order quantity and lead time with sales, and start at the OEM service page, which is where a retail or branded conversation begins. A short note on the numbers we share: we list grit, form and diameter as standard, and we confirm the rated speed against each model before an order ships, because that number has to come from the disc, not from a guess.

When the disc cuts less than expected

Under cutting is the quiet complaint: the disc looks fine, the machine sounds fine, but the panel is not going. The causes are usually one of these five, and each has a different fix:

Grit skip. Going from P80 straight to P320 leaves the P80 scratches under the finish; add the P150 and P240 steps and the surface clears.
Glazing or loading. A face that stops cutting and starts to burn is a grain that is too soft for the material, or a disc held in one spot; move to a coarser grit or a cleaner grain, and keep the tool moving rather than pressing in.
Edge or corner lift on the PSA. The hook-and-loop edge lifting is the form complaining about the job; for real stock removal switch to the 8-hole hook-and-loop disc on a flap disc holder and keep the PSA for the finishing passes.
RPM past rated speed. If the tool spins faster than the disc rating, slow the tool down or use a smaller diameter; do not run a disc past its printed maximum, because that is where the fragments come from.
Wrong form for the job. A mesh disc on a dry, low-dust job is paying for a feature you are not using; a PSA on a wet, high-dust job is the disc that clogs. Match the form to the dust load, not just to the grit.

For any of these, the sanding disc range shows the grit and form to reach for, the automotive repair notes give the sequence by material, and the abrasives glossary keeps the terms straight so you and your team are diagnosing the same problem. The thread through all five is that under cutting is almost always a match problem, not a bad disc; fix the grit, the grain, the form or the speed and the cut comes back.

Common mistakes, with the fix that actually moves it

The fixes are usually cheaper than the mistake. Here is what shows up most often on 5-inch work:

Skipping grits. P80 to P320 leaves the P80 scratches under the top coat; add the P150 and P240 steps in between.
Glazing on hard material. A face that burns instead of cuts wants a coarser grit or a cleaner grain, and lighter pressure, not more of the same.
Edge and corner lift on the PSA. Swap the form for the job: the 8-hole hook-and-loop on a flap disc holder for the aggressive passes, and keep the PSA for the finishing.
RPM past the rated speed. Confirm the disc's rating against the tool, and run the tool below it; a disc at 13,000 RPM is not the disc it was designed to be.
Using the wrong form for paint prep. Reaching for P80 on a panel that only needs P240 costs you in filler, because the P80 scratch shows through the next coat.
Buying the cheap pad and blaming the disc. A worn hook on the pad shifts the disc off square, and the panel shows a low spot the operator cannot find; swap the pad before you swap the disc, because the pad is the cheaper of the two and the more likely cause.

When you are not sure which grit to start on, the sanding disc range and the automotive repair notes show where the sequence lands for your material, and the quotation form is where the grit, the form and the standard get confirmed before the order ships. The one mistake that costs the most is the grit skip, because the coarser scratches under the finish are the ones nobody catches until the top coat is on, and by then the fix is a re-sand of the whole surface.

FAQ

Which grit do I start on for 5 Inch Sanding Discs, on bare wood or a primed surface? In many cases P80 to P120 knocks the surface down to a clean, even base, then P150 to P180 levels any filler and P240 brings it to the final prep step, with P320 under the top coat. The rule is that each step is finer than the last.

Are mesh 5-inch discs worth the premium over plain PSA paper? For high-dust jobs and any job with dust extraction, yes: the open face keeps the cut clean. For speed-sensitive finishing, the PSA is usually the pick because it swaps faster and costs less per disc. Start with PSA and keep mesh for the dirty jobs.

Can I run 5-inch discs on an angle grinder instead of an orbital? Not a PSA, and usually not a mesh either. The angle grinder runs past the rating of most 5-inch paper discs. The 8-hole hook-and-loop 5-inch disc on a flap disc holder is the compromise, and even there the tool speed has to stay under the disc's rated maximum. Confirm the number against the model.

What is the difference between 5-inch and 6-inch discs? The 5-inch on an orbital is the everyday finishing tool for panels and doors; a 6-inch covers more surface per pass. When you move from 5 to 6, the tool has to take the larger pad, and the disc's rated speed has to clear the tool's no-load speed. The grit choice does not change; the pad and the tool check do.

Which grit standard should I name in an enquiry? The P-number is FEPA or ISO 848. Name the standard in the order so a different scale does not slip in, and on a bulk or branded order it is a field on the spec sheet, not a footnote. The reference is at the FEPA grit standard, and the quotation form is where the standard, the grit and the form get sent in one place.

Do you do private label or wholesale on 5-inch discs? The OEM service page covers the label, the packing and the spec sheet for a branded or retail run, and the quotation form takes the grit, the disc form and the standard so the order starts with the fields that make or break it.

Which grain for plastics or slick material? Silicon carbide, because aluminium oxide burns on slick surfaces instead of cutting. The grain decides how the cut feels, and the grit decides how much comes off; change one at a time so you can tell which one moved the result.

My disc stopped cutting mid-panel. What is wrong? Usually loading or glazing, or a grit that is too fine for the material. Step the grit, move to a cleaner grain, and keep the tool moving instead of pressing into the face. The abrasives glossary defines the terms so you and the shop are diagnosing the same problem.

Before you buy

A short compliance and purchasing checklist. This is a reminder, not a substitute for your own site rules, and under compliant use with the right protection the risk of these tools is reduced, not zero.

Confirm your tool's maximum no-load speed is below the disc's rated maximum working speed before every use, and where the disc does not print a number, confirm the rating against the model.
Check the pad or holder matches the disc form: hook on the sander meets loop on the disc, or loop on the sander meets hook, and the 8-hole disc clamps onto a flap disc holder, not a PSA pad.
Fit and keep the tool guard on at all times; it is the first defence against a disc failure.
Wear eye and face protection, and use dust extraction with the right filter plus the respiratory protection that matches the dust load.
State the grit, the form and the grit standard (FEPA or ISO 848) in every enquiry so the order does not mix scales.
Confirm the grain against the material you are cutting, because aluminium oxide, silicon carbide and ceramic do not all behave the same on the same surface.
Store the discs away from heat and damp, and ship them in the packing they came in; a warped or wet disc does not cut the way the spec sheet says it will.
Follow the disc maker's install notes, and check the part and the disc for heat and scratch depth on thin or soft material before you change grits.
Confirm lead time, minimum order and packing for any wholesale or private label run, and start the order at the quotation form.

If you tell us the material, the finish you are aiming for, the tool you run and the grit standard you buy to, the team can pre-select the grit band and the disc form from the 5 Inch Sanding Discs range to start from. Send the four and the sequence comes back with the order.