The short answer
You can sharpen a knife with sandpaper by wrapping wet/dry paper around a genuinely flat backing and working through a grit progression — roughly 400, then 800, then 1500 to 2000 — holding a consistent 15 to 20 degree angle per side and using edge-trailing strokes so the abrasive does not tear. It works on any common folding knife steel, it costs a few dollars instead of a hundred, and the limiting factor is not the paper — a sharpening stone is more convenient, but flatness per dollar is not close. It is how flat your backing is and how steady your angle is.
Sandpaper earns its place for two jobs in particular: restoring a badly dulled or chipped edge without buying a coarse stone, and reprofiling a factory bevel you want to change. It is a poor choice for high-vanadium supersteels and a clumsy choice for recurves unless you wrap the paper around something round.
What you actually need
The shopping list is short, and the cheapest item is the one that decides whether the result is good.
| Item | What to get | Why it matters |
|---|---|---|
| Abrasive | Wet/dry paper in 400, 800, 1500 and 2000 grit | Wet/dry paper uses silicon carbide or aluminum oxide and survives water; plain woodworking paper falls apart |
| Backing | Glass plate, granite floor tile, or a flat whetstone | Paper conforms to whatever is under it — a soft surface rounds your bevel |
| Lubricant | Water with a drop of dish soap | Floats away swarf and stops the paper loading up |
| Marker | Fine permanent marker | The angle test that tells you the truth about your bevel |
| Tape | One strip of painter's tape | Holds the sheet down and protects the edge of the glass |
| Strop | Leather with compound, or cardboard with green compound | Removes the burr and turns a 2000-grit scratch pattern into a working edge |
Two notes on the abrasive itself. Silicon carbide wet/dry paper cuts faster and lasts longer wet than dry, and it handles hardened steel better than aluminum oxide. If you only buy one sheet size, buy a multi-pack that includes 400 through 2000 — you will use every grit eventually.
Grit progression that makes sense
Grit numbers only mean something relative to each other. Here is the approximate abrasive particle size for common wet/dry grits, so you can see why 400 to 800 to 1500 is a logical jump and 400 straight to 2000 is not.
| Grit (ANSI/CAMI) | Approx. particle size | Job |
|---|---|---|
| 320 | ~46 microns | Removing chips, resetting a damaged apex |
| 400 | ~35 microns | The workhorse grit for a dull but undamaged edge |
| 600 | ~26 microns | Intermediate cleanup if you skip 800 |
| 800 | ~22 microns | Refining the scratch pattern, setting a working edge |
| 1000 | ~18 microns | Optional; good stopping point for slicing edges |
| 1500 | ~13 microns | Pre-polish |
| 2000 | ~10 microns | Near-mirror; best followed by a strop |
The rule of thumb: do not skip more than one step. Going from 400 to 2000 means the 2000 sheet spends its life removing 400-grit scratches instead of polishing an edge. Two sheets of each grit will outlast one sheet of every grit bought in a panic.
For a general-purpose folding knife, stopping at 800 or 1000 gives a toothy edge that bites into rope, cardboard and packaging. Going to 2000 and stropping gives a cleaner push cut and a nicer-looking bevel, but a working EDC knife rarely needs more than 1000.
Step by step
1. Set up a flat surface
Tape a sheet of wet/dry paper abrasive-side-up to glass, a granite tile, or a whetstone you no longer trust. Press the paper flat from the center outward so no air pockets remain. If the paper has a slight curl, tape all four edges — a lifted corner will catch the edge and roll it.
2. Find your angle with a marker
Colour the bevel with a permanent marker, then take three or four strokes at your intended angle. Look at where the marker is gone. Ink removed at the very edge means your angle is too steep and you are only touching the micro-bevel. Ink removed at the shoulder of the bevel means your angle is too shallow. Adjust until the ink comes off across the full width of the bevel.
This test takes two minutes and saves you from grinding a new angle by accident.
3. Use edge-trailing strokes
Push the edge away from the abrasive — spine first, edge last — as if you were stroking the blade along the paper. Edge-leading strokes (edge first) dig the apex into the paper and tear it, which both ruins the sheet and rolls the edge. Keep the pressure light; the abrasive cuts, your arm does not.
4. Count strokes and alternate
Twenty to forty strokes per side per grit is a reasonable range for a folding knife. Alternate sides every ten strokes so you do not build a lopsided bevel. If one side takes noticeably more work, stop and check whether the bevels were asymmetric to begin with — many factory edges are.
5. Read the burr
When the first grit has done its job, a burr forms along the full length of the opposite side. Feel for it by drawing a fingertip across the edge at a right angle, never along it. You are checking for a consistent, fine catch from heel to tip. An inconsistent burr means an inconsistent angle, which is the single most common reason a sandpaper sharpen "doesn't work."
6. Progress, then strop
Move up the grits, repeating the marker check once at the start of each step. After 1500 or 2000, strop on leather or cardboard with compound, ten to twenty passes per side, edge-trailing. That removes the last of the burr and leaves an edge that cuts paper cleanly.
Backing matters more than grit
If you take one thing from this guide, take this. Sandpaper is a thin, flexible abrasive. Every bit of softness under it becomes a rounded bevel, and a rounded bevel feels sharp but slides off a tomato skin and struggles with cardboard.
Glass is the flattest cheap option and does not wear. A granite tile from a hardware store is nearly as flat and less likely to shatter. A flat whetstone works if it is genuinely flat — check it with a straightedge, because dished stones are common. A wooden block or a mousepad is fine for convex edges and useless for a crisp bevel, so know which result you want before you choose the backing.
The same logic applies to paper thickness. Wet/dry paper is thin, so the abrasive sits close to the backing and the bevel stays crisp. Cheap paper is thicker and spongier, and behaves like a soft backing even on glass.
Which steels work, and which need diamonds
Sandpaper handles carbon and low-alloy stainless steels easily. It handles mid-range particle metallurgy steels with a bit more time. It struggles where the carbides are harder than the abrasive itself.
| Steel family | Examples in the catalog | Sandpaper verdict |
|---|---|---|
| Simple carbon and low-alloy | 1095, 8Cr13MoV, 9Cr18MoV | Fast and easy; any grit progression works |
| Mid-range stainless | 14C28N, Nitro-V, AR-RPM9 | Works well; expect more strokes at 400 |
| Semi-stainless tool steel | D2 | Works, but slow — D2 resists abrasion by design |
| Particle metallurgy stainless | S35VN, M390, CPM-20CV | Possible but inefficient; diamond is the right tool |
| High-vanadium | S90V, CPM-10V | Skip sandpaper; use diamond plates or film |
The reason is hardness. Silicon carbide sits around 2,500 on the Vickers scale; the vanadium carbides in high-vanadium steels are harder than that, as Knife Steel Nerds documents in its steel-by-steel carbide breakdowns. When the carbide is harder than the abrasive, you are polishing the carbide with something that cannot cut it, and the session turns into an hour of arm work.
For the middle of that table, sandpaper is genuinely practical. A CJRB Lago in AR-RPM9 at $49.98 responds to a 400/800/2000 progression in a normal session. A CJRB Tundra in D2 at $69.99 takes longer but is still workable. A CIVIVI Baby Banter in Nitro-V at $70, hardened to 59 to 61 HRC with a flat grind, is close to ideal for this method because the flat grind gives you a wide bevel to read. An Artisan Cutlery Tradition V2 in S35VN at $89.99 is where you start thinking about diamond. An Artisan Cutlery Tomahawk in M390 at $224.99 is where sandpaper stops being the sensible answer.
Mistakes that waste an hour
| Mistake | What it looks like | Correct approach |
|---|---|---|
| Soft backing | Edge feels sharp but will not bite | Glass, granite or a flat stone |
| Edge-leading strokes | Paper tears, edge rolls | Stroke spine first |
| Skipping grits | 2000 sheet does all the work | One step at a time |
| Too much pressure | Paper glazes, bevel rounds | Light pressure, more strokes |
| Not raising a burr | Edge looks polished, still dull | Stay on the coarse grit until the burr is continuous |
| Ignoring the plunge line | Rounded heel, sharp tip only | Check the marker at both ends |
Sandpaper versus stones
Sandpaper wins on cost, on flatness per dollar, and on coarse work. A sheet of 320 costs less than a coffee refill, and a glass plate is flatter than most inexpensive combination stones. It loses on convenience, on mess, and on longevity — a sheet is a consumable.
Water stones win on feel and on repeatability for maintenance sharpening, which is why most people end up with a 400/1000 combination stone and a strop after a year of sandpaper. If you want to see how the alternatives compare, our breakdown of sharpening systems covers diamond, ceramic and guided systems, and the whetstone guide covers the soaking and angle routine for the stone side.
Use sandpaper when you need to remove metal — chips, a reprofile, a neglected bevel. Use a stone when you need to maintain an edge you already like.
FAQ
Can sandpaper actually sharpen a knife, or is it a gimmick? It sharpens. Silicon carbide wet/dry paper cuts hardened steel, and flat paper on glass produces a better bevel than a dished budget stone. The technique is the same as any flat abrasive; only the consumable is cheaper.
What grit should I start with on a dull pocket knife? Start at 400 for a dull but undamaged edge. Drop to 320 only if there are visible chips or the bevel needs resetting. Starting coarser than necessary just removes steel you cannot put back.
How many strokes does it take? Twenty to forty per side per grit for a typical folding knife, alternating sides every ten. High-vanadium steels take far more, which is the signal to switch to diamond rather than push harder.
Is it safe to use water on the paper? Yes — wet/dry paper is designed for it. A drop of dish soap in the water helps float away metal particles. Do not use oil on adhesive-backed sheets; it can soften the adhesive and let the paper slip.
Can I sharpen a serrated or recurved blade this way? Recurves, yes: wrap the paper around a dowel or a sharpening rod and work each scallop section. Serrations are better handled with a tapered rod, covered in our guide to sharpening serrated and recurved blades.
Do I need to strop after 2000 grit? You do not have to, but it is the cheapest improvement available. Ten to twenty edge-trailing passes on leather with compound removes the residual burr and noticeably improves push cutting.
Where to go next
If you are new to sharpening entirely, start with the beginner's guide to sharpening an EDC knife for the fundamentals, then read our sharpening angle comparison before you commit to a number. Once the edge is sharp, stropping is what keeps it there for weeks instead of days.