How to Match Auto Body Sanding: Your Sanding Disc

The short answer on Auto Body Sanding 🚗

Here is the rule that governs nearly every auto body sanding decision on a panel: each grit step must be finer than the last, and P220 is the anchor grit where filler work ends and fine blending begins. For a panel in primer, P180 to P220 levels and blends it for the next coat; for filler, P120 to P180 to P220 does the job; on bare metal, P150 to P220 opens the surface and brings it even. The second half of the rule is that the disc must suit the shape of the panel: curved panels want a disc that conforms, so a mesh sanding disc sits honest over the curve, while flat work is more forgiving with a hook-and-loop disc on a pad.

Two scenarios where the rule bends. Heavy panel filler on a deep quarter panel sometimes starts a step coarser, P80 to P120, before the P220 sequence can even be reached. And a thin panel close to the metal will not take a coarse grit at all — P120 and up is as coarse as you can run, because a coarser grit has a real chance of burning through the remaining surface. If you only remember one number for everyday panel work, it is P220: it is where filler work is considered finished and the fine work starts.

For the full range of shapes and grits we supply, start from the sanding disc range, and keep the abrasives glossary open whenever a label term is unfamiliar. Two habits make the whole process repeatable instead of a guess: name the grit standard you are buying to (FEPA or ISO 848), and match the disc to the pad and the tool before the first pass.

How a grit number is read on the FEPA scale

The grit number is a FEPA or ISO 848 designation, and the higher the number, the finer the cut. In the auto body world the working ladder looks like this:

P80 – P120 🧱 — coarse removal: heavy filler stock reduction and bare metal open up.
P150 – P180 ⚙️ — leveling: bringing primer and filler down to roughly even.
P220 📏 — the anchor grit: filler is finished, the panel is even and ready for the next stage.
P320 – P400 ✅ — fine blending and surface prep before paint.
P600 – P1000 🪞 — post-paint leveling when the surface has already been through P400.
P1500 – P3000 ✨ — polishing and wax prep on a surface that is close to its final state.

We stock from P60 up to P5000 across the disc range, and the FEPA scale is what most international buyers quote, so naming the standard in every enquiry keeps you from the classic mix-up where one supplier is quoting FEPA and another is on an older scale and the same number means two different cuts. The reference is at the FEPA grit standard (ISO 848).

The reason the ladder matters more than any single grit is that every scratch you leave has to be erased by the next grit or it survives under the next coat and shows through in the light. Skipping a step is the single most expensive mistake in auto body sanding, and it is the one that rework costs come back for.

How Auto Body Sanding actually works

A panel gets sanded two ways: by hand on a block or by machine on a pad. The machine is a dual-action or orbital tool, and the disc spins on the pad in a small circular orbit that moves constantly. Two things decide the outcome. One is the grit, which sets the scratch size, and two is the motion, which decides how fast the scratch pattern rotates through the surface. If the motion is wrong for the grit — a too-coarse grit held in one spot, or a too-fine grit being pressed into the panel — the result is a scratch that the next grit has to fight instead of a surface that is ready for it.

That motion is why backing matters on a panel. A mesh sanding disc conforms to the curve of the panel because the mesh is stitched into an open weave that stretches and folds, so the disc sits flat over a wheel arch and does not leave a flat spot where a stiff paper disc would. The hook-and-loop option is a disc with a Velcro-style backing that locks to a matching pad, which suits flat panels and speed work where you swap the disc between grits in seconds. The shape of the backing changes the feel of the job more than most people expect, because a disc that will not conform puts every flat spot it makes straight into the panel.

The trade between the three things is the whole of this article. The cut is set by the grit and the grain. The finish is set by how even the scratch pattern is, which is the grit sequence and the backing. The life is set by how the disc wears, which is grain and bond. Get the grit wrong and you either remove too much or not enough; get the backing wrong and the panel shows flat spots; get the grain wrong and the disc packs or glazes and stops cutting. Each of the three is a separate decision, and each is the thing that decides the outcome of the finish.

Grain and bond: what is under the grit

The grain is where most of the auto body sanding outcome is decided. Aluminium oxide is the default on primers and fillers: it is tough, it cuts evenly, and it keeps its edge through the dust of a filler job. Zirconia alumina shows up where the grain has to stay open, on the tougher fillers, on glass, and on edges where the dust would pack a softer grain. Silicon carbide moves into the bare metal and some plastics, because it is harder and sharper, and it suits cutting through cured paint into metal; it also scratches deeper, which is why it belongs in the early part of the sequence, not the last. Ceramic is the premium, longest-wearing option, and it earns its place on high-volume work where cost per panel, not price per disc, is what you are managing. The grain property behind each of these — hardness, toughness, sharpness — is what makes each fit a different part of the sequence.

The bond is the second half. The bond is what holds the grain to the backing, and a body-shop bond is chosen to survive a long cut on filler and primer without shedding early. A disc that sheds its grain on the first pass is a cheap-looking disc that is expensive over a full panel, because the panel gets more dust and the next grit has to work harder to cover what the last grit left behind. A good bond keeps the grain in place until the grit itself is genuinely worn, which is the difference between a disc that lasts a panel and one that lasts a corner of it.

The backing is where the shape decision lands. A mesh disc conforms and self-cleans through the open weave. A hook-and-loop disc locks to a pad and swaps in seconds. A solid paper disc is the stiff one, and it is the one that makes flat spots on a curve. Pick the grain that will not pack on your substrate, then the grit that matches the material left on the panel, then the backing that matches the shape of the panel, and the sequence takes care of itself.

Choosing the disc shape for a panel

This is the backing decision spelled out as a list, because it is the one buyers ask about most:

Mesh disc ✅ — conforms to the curve, self-cleans, and lasts through a panel. The top pick for body work on curved panels, and the one to reach for over any painted area you want to keep.
Hook-and-loop disc ⚙️ — the speed tool for filler and general work. The hook and loop backing is the quick-swap side of the system: it locks to a matching pad and releases in seconds, so you re-grit the tool between passes without taking anything apart. It is cheap to re-grit, but the orbit action cuts the paint you do not cover, so you mask around the work. The 6-inch 17-hole hook-and-loop disc is the common format on a 5-inch pad.
Non-hole solid disc 🧱 — a paper disc with no centre hole, for work where the pad should not show through. It is stiff, so it suits flat panels and touch-ups rather than a full curved panel.
PSA paper disc 📏 — the economical option for light blending. It does not conform on a curve, so it is the pick for flat panels and the lightest work, not the primary pass on a body panel.

The rule of thumb for a shop: use a mesh sanding disc over any painted area you want to keep, and use a hook-and-loop disc where speed and swapping between grits matters more than the surrounding finish. The 5-inch mesh sanding discs page is where to confirm the grit and size against the pad you run.

Choosing by material and finish line

The same panel runs a different sequence depending on what is on it. The grit sequence shifts by the stage the panel is at:

Primer-sanded panel 🎨 — P180 to P220. This is the classic body-shop path: P180 breaks the top of the primer and levels it, P220 brings the whole panel even.
Filler 🧱 — P120 to P180 to P220. P120 does the coarse leveling when the filler is on thick, P180 and P220 take it to even.
Bare metal and aluminium 🚗 — P150 to P220. P150 opens the surface for the next coat, P220 brings the whole area even.
Painted panel, light blending ✅ — P320 to P400. P220 is too coarse for a light pass over a finished panel, and it will cut through the paint, so the fine grit is the move.
Deep repair, heavy filler build-up 🪑 — P80 to P120 to start, then the P180 to P220 path. This is the exception: when the filler is a full repair patch and not a light skim, you start a step coarser and work down.

The rule underneath all of it is the same: every grit you run has to erase the scratches of the one before it. If the coarser scratches survive under the next coat, the panel shows it in the light, and that is why a skipped grit is the mistake you pay for in rework.

The 220 gate, in one line

Treat 220 grit as the single gate that separates filler work from the fine work: if the panel has not been run through the 220 step, it is not ready for the next stage, no matter what the scratch pattern looks like. That is the one number that keeps the sequence honest.

A worked example: a quarter panel in primer and filler

Walk through a rear quarter panel on a car. The panel is in primer, the filler is in the wheel arch, and the bare metal is around the panel gap. The filler area gets the full sequence: P120 for the coarse leveling of the thick filler, P180 to bring it down, and P220 to even it. The surrounding primer goes P180 to P220, which blends the filler edge into the primer so there is no line where the filler stops and the primer starts. The bare metal around the gap is P150 to P220, and P220 is what brings the sanded edge into line with the rest of the panel.

The test at P220 is the one that matters: run your hand across the panel and it should glide with no ridge or valley. P220 is the grit that makes the panel even under the next coat, so treat it as the gate — skip it or half-do it and the finish line will show up later, in the light, where it is the most expensive place to find it. The grit bands and the disc types for each are listed on the automotive repair sanding use page and in the sanding disc range.

The fine finish beyond P220

P220 is the anchor, not the end. After it, the work continues to P320, P400, and in a shop to P1000 and P3000 for the post-paint pass. The fine work is where the panel goes from sanded to ready for paint, and it is where the scratch pattern has to be erased, not just covered.

Wet sanding is the separate discipline that sits on top of the fine grits. Working the disc under water with a fine grit keeps the disc from glazing, keeps the dust in check, and lets the fine grit cut instead of loading. The pressure drops a lot and the pad keeps moving; stopping in one spot with a fine grit rounds the contours you just sanded, which is the mistake that shows up as a soft panel in the light. Wet-sanding with P600 or P800 levels the P400 scratches, and then the wax or compound takes the surface to its final state. The fine grits are forgiving but slow, and the rule that still holds is that every grit erases the last one's scratches. For a body panel, the practical end of disc work is P400 or P600 on a dry mesh disc, and after that the hands take over with wax and compound.

P220 to the fine grits: the last stretch of the sequence

Once the panel is through the P220 gate, the remaining work is the stretch from P220 to P400 to P1000 and beyond. This is where most shops either slow down or skip the steps, and the two habits that keep the surface clean are: change the grit before the scratches of the last grit show, and never hold the pad in one spot on a fine grit.

P220 to P320 — the bridge grit: the scratches from P220 have to be erased before the paint stage, and P320 is the grit that does it.
P320 to P400 — the paint-stage grit: this is the grit the shop finishes the panel on before the basecoat, and it is the grit that leaves a surface the paint sits evenly on.
P600 to P1000 — the post-paint leveling grit, run dry on a mesh disc or under water on the pad, when the basecoat has cured and you need to erase the P400 scratches before the clear or the compound.
P1500 to P3000 — the polish and wax grit, run light and moving, when the panel is already through P1000 and you want the surface at the final state.

The habit that separates a clean panel from a soft one is the grit change. When you step from P220 to P320, the P220 disc is usually spent, because the coarse grit burns through and the fine grit wants a fresh, open face. Plan one disc per grit band and the panel stays clean; carry a P220 disc into the P320 stage and the scratch pattern shows through the paint, and that is the panel that shows in the light a week later.

Tool and pad: the setup before the first pass

The disc is the last half of the match; the tool and the pad are the first half. A body shop runs the same disc on three different setups and gets three different finishes, so the setup has to be decided before the grit, not after. The three that show up in a body shop are:

Dual-action (DA) pad on an orbital tool — the default for auto body sanding, because the orbital motion rotates the scratch pattern so it does not sit in one place. It is the safest tool on a curved panel and the one that keeps the panel even.
Variable-speed orbital on flat work — for flat panels and the light blending pass, where the speed control lets you run the fine grits slower than the tool's no-load speed. The disc wears more evenly at the lower speed, and the cut is gentler on a painted panel you want to keep.
Detailing pad on the fine grits — for P400 and finer, where the pad is small and the work is a blend, not a full panel. The pad is the size of the panel area you are working, and the grit is P400 to P1000.

The setup rule that keeps the finish honest: the pad has to be the right size for the panel, and the tool speed has to be under the disc's rated speed. A pad that is too big for the panel puts the orbital motion into the surrounding paint, and a tool that is too fast flexes the disc and the panel shows the flex as a soft spot. Confirm the rated speed of the disc against the tool's rating, and when in doubt, run the tool at no load and stay under the disc's rated maximum. The pad also decides the disc: a 5-inch pad takes a 5-inch hook-and-loop disc, and the 6-inch pad takes a 6-inch disc, so the pad size and the disc size have to match before the first pass.

The hook-and-loop disc is where the setup shows most. A disc on a clean pad cuts clean; a disc on a pad that is packed with dust from the last grit cuts like the last grit, not the new one. The hook and loop side of the system is what makes that change fast: pull the disc off, wipe the pad, and the new grit is on in seconds. The habit that keeps the shop honest is to clean the pad when you change the grit, or run a fresh pad on the new grit, because the pad is the thing that carries the old grit into the new stage. A hook-and-loop disc that is not matching a clean pad is a disc that is cutting the wrong grit, and the panel shows it.

Storing and maintaining the discs

The disc is only as good as the shelf it comes from. A body shop that keeps its discs packed with dust gets a disc that packs on the panel, and the dust that is in the shop is the dust that ends up in the grit. Three habits that keep the shelf honest:

Sealed packaging, off the floor — the discs stay in their bags until the pass, so the shop dust does not settle into the grit before the panel sees it.
One grit, one bin — the P220 disc, the P180 disc, and the P400 disc do not share a bin, because a P220 disc that has been sitting next to a P80 disc carries the P80 scratches into the P220 stage.
The pad and the disc, matched — the hook-and-loop pad and the hook-and-loop disc are a pair, and the pair is what keeps the disc from shedding on the first pass. A pad that is too small for the disc, or a disc that is the wrong grit for the pad, is the pair that shows up on the panel as a soft spot.

The shelf habit that keeps the shop honest is that a disc that has been through one panel is not the disc to start the next panel with. The grit is worn, the face is packed, and the panel shows the change mid-pass. Plan one disc per grit band, per panel, and the waste stays where it belongs, on the disc, not on the panel. For the grit and the backing you plan against, the 5-inch mesh sanding discs page is where to confirm the stock, and the automotive repair sanding use page gives the sequence by panel stage.

Speed, dust and safety

The speed side is the one that is easy to get wrong. A DA tool's orbital motion and the pad diameter together set the line speed of the disc, and every disc and tool has a rated maximum. Keep the tool below the disc's rated speed and confirm it against the tool's rating. On a dual-action pad, the tool speed is the limit; check the pad and the tool manual before you start the auto body sanding pass. Running a disc on a fast tool makes it flex, heat, and wear unevenly; running it on a slow tool makes it feel soft and cut less. The line-speed mismatch is the quiet failure mode — nothing looks wrong until the finish shows it.

The dust and PPE side is the one that turns a routine panel into a long-term exposure problem. Body-shop dust is a fine mix of primer, filler, and paint, and the risk is breathing it in. The controls are extraction at the panel, PPE for the eyes and face, and respiratory protection matched to the load. The U.S. baseline for PPE general requirements is at OSHA 29 CFR 1910.132, and a practical reading of abrasive work with portable tools is at CCOHS "Abrasive Wheels". The honest message is that compliant use lowers the risk, it does not eliminate it; the extraction running at the panel, the right PPE, and a clean disc are what you rely on, not luck.

Two failure modes deserve their own line. A disc run on a too-fast tool separates at the edge and cuts the panel unevenly; a disc that is past its useful life packs and glazes and stops cutting, and the panel shows the change mid-pass. Both are preventable, and both start at the label and at the decision to swap the disc before the panel shows the wear. The rule is the same one from the top: read the disc, read the tool, and only then start the panel.

Cost, life and lead time

On cost, the number that matters on a panel is cost per finished surface, not cost per disc. A mesh disc cuts more per unit of the panel and lasts longer, so the per-panel cost is usually lower than the sticker price gap suggests. A hook-and-loop disc is cheaper per unit and swaps in seconds, which suits touch-up work and light blending where you are not doing a full panel. Grit matters for wear: a coarse grit on filler burns through fast, and a fine grit like P320 to P400 lasts because the cut is light. Planning for the grit change is what keeps the shop from paying for rework — when you step from P180 to P220, the P180 disc is usually done, because a packed P180 carried into the P220 stage is the disc that packs the panel. Plan one disc per grit band and the waste stays where it belongs, on the disc, not on the panel.

For a private-label or bulk run, the OEM & private-label service page lists what we put on the label and packing, and the minimum order quantity and the lead time are confirmed against the order. A regular order for a stocked grit in a common size ships fast; an off-grid grit or a custom label run takes longer, because the grain, the backing, and the label all have to line up. For a branded run, ask for a sample against the spec before the full order so the grit, the backing, and the label all match what you expect on the panel.

Common mistakes and how to fix them

The fixes are usually cheaper than the mistakes. Here is what shows up most often on a panel, with the fix that actually moves the problem:

Skipping grits — going from P80 straight to P220 leaves P80 scratches under the topcoat. Add the P120 and P180 steps and the panel clears.
Pressing into the panel — pressing into a disc packs the grit and glazes it, which is the opposite of cutting more. Lighter pressure and a moving pad bring the cut back.
One disc across grits — carrying a disc from P180 into P220 carries the scratches forward. Plan one disc per grit band.
Coarse grit over cured basecoat — P120 over a finished panel cuts through it. The light pass is P320 to P400, and the coarser grits belong on filler and primer, not on the finished surface.
Forgetting the dust — no extraction means the panel is dusted with every pass and the shop floor gets fine dust that does not settle. Extraction at the panel is the control, and it is the one that protects the finish and the people in the shop.
Ignoring disc wear — a disc that is past its useful life packs and glazes and stops cutting. Swap it before the panel shows the change.

For any of these, the sanding disc range shows the grit and the backing to reach for, and the automotive repair sanding use page gives the sequence by panel stage. The thread that runs through all of them is that the disc is only as good as the grit, the backing, and the sequence you matched it with before the panel started; most of the complaints are really mismatch complaints wearing a grit's name.

FAQ

Do I use P220 straight into paint? P220 is the anchor grit where filler work ends and fine blending begins. For a panel that is in primer or filler, P220 is the gate to the next stage, and for a panel that is already through the filler, P320 to P400 is the fine work. The grit you end on depends on what is left on the panel.

Mesh or hook-and-loop for a curved panel? A mesh disc conforms to the curve and self-cleans through the open weave, so it is the pick over a painted area you want to keep. A hook-and-loop disc is the speed tool for filler and flat work, where you swap the disc between grits in seconds. For a body panel on a curve, the mesh is the safer match.

What grit sequence do I run on filler? P120 to P180 to P220 is the standard filler path: P120 for the coarse leveling of thick filler, P180 to bring it down, and P220 to even the whole panel. If the filler is light, start at P180 and step down to P220.

How long should a disc last? It depends on the grit and the grain: a coarse grit on filler burns through fast, and a fine grit lasts because the cut is light. The habit that keeps it honest is one disc per grit band, so you do not carry a packed P180 into the P220 stage and pack the panel.

What tool speed do I run? Confirm the rated speed of the disc against the tool before the pass, and keep the tool below it. On a dual-action pad the tool speed is the limit, so check the pad and the tool manual. When in doubt, run the tool at no load and stay under the disc's rated maximum.

How do I control the dust? Extraction at the panel, the right PPE for the eyes and face, and respiratory protection matched to the load. The OSHA PPE general requirements are a useful baseline at OSHA 29 CFR 1910.132, and the CCOHS reading is at CCOHS "Abrasive Wheels".

What standard should I name in an enquiry? Name the FEPA or ISO 848 grit plus the size and the backing, so the order is not mixed with a different grit scale. The reference is at the FEPA grit standard, and the request a quotation page is where to confirm the grit and the size against what we stock.

Before you buy

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

Confirm your tool's maximum speed is below the disc's rated speed, and keep the tool under that limit on every panel.
Check the pad size and the disc backing match: a hook-and-loop disc needs a matching pad, and a mesh disc needs the pad that fits the weave.
Wear eye and face protection, run dust extraction at the panel, and use respiratory protection matched to the dust load.
Name the grit standard (FEPA or ISO 848) in every enquiry so two suppliers do not ship two different cuts of the same number.
Check the inspection report and the certificates for any run you are putting on a panel, and confirm them against the order.
Store the discs away from the dust and the heat, and keep the hook-and-loop pads and the mesh discs in their own packaging so they do not pack with the shop dust.
Follow the install notes for the pad and the tool, and check the panel for heat and scratch depth on thin metal before the next grit.
For a bulk or private-label run, confirm the minimum order quantity and the lead time on the OEM & private-label service page, and start with the request a quotation form.

If you tell us the material on the panel, the finish you are aiming for, and the tool you run, we can help you pick the grit and the backing to start from. Send the three and we will work the sequence with you on the request a quotation page.