Most woodworkers know how to sharpen. Follow the grits, hold the angle, strop at the end. An afternoon of practice and you've got the sequence.
The question they get wrong is simpler: what is sharp?
If you don't know what you're producing, you can't tell when you've produced it. You can spend twenty minutes on stones and end up with a shinier tool that cuts no better than when you started. Or you can spend four minutes and stop the moment the diagnostic says done. That moment is the only one that counts.
What sharp actually is
Sharp is two polished surfaces meeting cleanly at an acute angle.
That's the whole definition. A cutting edge is where two faces intersect: the bevel face, ground back from the edge at your working angle, and the back face, the flat underside of the iron or chisel. When both faces are polished flat and they meet without rounding or damage at the apex, the edge is sharp. When either face is scratched, or when the apex itself is rounded even slightly, the tool is dull.
Most dullness is invisible. A dull edge reflects light as a thin bright line right at the tip, because that tiny rounded section acts like a mirror. A sharp edge has no flat section to reflect. Hold the edge under raking light — angled toward the edge, not perpendicular. A bright line means more work. An edge that seems to vanish into darkness means you're close.
The practical implication: you can't sharpen past a geometry problem. If the back face of your iron isn't flat, no amount of bevel work closes the gap. The two faces can't meet cleanly if one of them is bowed. You flatten the back once, thoroughly, and then leave it mostly alone. The bevel face is where the ongoing work happens.
The wire edge
One diagnostic tells you when you've done enough at each stage of honing. It's called the wire edge, and once you learn to feel for it, you'll stop wasting time at grit levels you've already finished.
When you hone the bevel face, you're removing metal from the high side of the angle. That metal doesn't disappear — it deforms, folding over the back face as a thin wire right at the apex. Run your fingertip very lightly off the edge (never along it), catching the back face just past the tip. The wire feels like a slight catch or roughness. Some people barely detect it at first. That's fine. It's there.
If you feel the wire, you're done at that grit. The abrasive has cut all the way through to the apex. Flip to the back, two or three strokes flat on the stone, and move on.
If you don't feel a wire, keep going. Not because you haven't done enough strokes. Because the physics isn't finished. The edge tells you when it's ready.
Why dull costs more than time
The obvious argument is that sharp tools are faster. True, and beside the point.
The real cost of dull is that a dull edge does different work. It doesn't cut wood fibers — it compresses them, tears them. In softwoods, you mostly notice the extra effort. In hardwoods, in anything requiring a clean surface — fitted joints, chopped baselines, mortise walls — a dull edge leaves torn grain that a sharp edge would have sliced.
You're not just working slower. You're making different cuts. A paring chisel that isn't sharp won't register to a scribed line; it'll skid. A plane iron that isn't sharp won't leave a burnished surface. The standard that matters — a joint that seats itself under hand pressure alone — is unreachable with a dull edge regardless of technique.
Dullness is also cumulative. A tool that was sharp at the start of a session gets progressively worse through the day. The woodworker who doesn't strop compensates with more pressure and more passes, which compounds the problem. The bench strop breaks that cycle.
The three geometries
Before you can sharpen, you need to know what geometry you're maintaining.
Flat bevel. The entire bevel face polished flat. Clean and simple to verify — lay the iron on the stone and check contact across the full face. The limitation: every session works the full face, which grows over time. Honing gets progressively slower. Fine for narrow chisels and tools you don't use constantly.
Hollow grind with micro-bevel. A grinding wheel cuts a concave hollow into the bevel. You then raise the angle slightly — a degree or two — forming a narrow secondary bevel right at the cutting edge. That tiny secondary bevel contacts the stone over a small area, so honing is fast. The hollow also creates self-indexing registration: the heel and the edge contact the stone simultaneously, so the angle finds itself. You regrind when the secondary bevel has grown wide enough to slow you down, typically every five to ten sessions for plane irons you use hard. Most efficient system for bench plane work.
Micro-bevel on flat. Establish a flat primary bevel, then raise the angle slightly for final honing. Combines the simplicity of flat with the speed advantage of a small contact area on the fine stones. Slightly less self-indexing than a hollow grind. Works fine.
Any of these produces a sharp edge. The choice is about maintenance rhythm, not edge quality at the tip.
The honing sequence
Coarse to fine. Back face at the end of each stage. Strop last.
Coarse (when there's a chip, after grinding, or when the edge is seriously degraded): Remove metal fast. Get the bevel flat and the scratches uniform. Raise a wire, remove it, move on. Don't linger here — those coarse scratches need to come out at every subsequent stage.
Medium (400–600 grit): Transition the scratch pattern. Raise a wire, remove it.
Fine (1000–1200 grit): Working sharpness. For most work in most woods, this is enough. Raise a wire, remove it.
Ultrafine (4000–8000 grit): Required for difficult or reversing grain, paring cuts that need to register precisely to a line, any surface you'll actually look at. The difference between fine and ultrafine shows up most in figured wood — fine tears, ultrafine slices. Raise a wire, remove it.
Strop: Chromium oxide compound on leather — green stick, available anywhere sharpening supplies are sold. Pull the bevel across the strop with spine leading and edge trailing. Never push the edge into the leather. Five to eight passes. Flip, pull the back face flat, three or four passes. Alternate until no wire is detectable and the edge passes the light test.
The strop is not optional for fine work. It removes the microscopic wire that even the finest stones leave behind, and it produces a polished apex the stones can't match. A well-stropped edge is noticeably different in use.
The bench strop
One more practice worth establishing: keep a dedicated strop at the bench, loaded and ready.
During a long session, tools dull gradually. The woodworker who doesn't catch this starts compensating — more pressure, more passes — and the quality of the work drops without any obvious moment of failure. Every twenty or thirty minutes in heavy work, or when a cut that should feel easy starts feeling like work: set the tool down, take ten passes on the strop (five bevel, five back), return to work. Forty-five seconds. It extends the time between full sharpening sessions by a factor of two or three.
The strop at the bench becomes a reflex. That's when it actually works.
When you're done
Two checks. Both have to pass.
Wire test: No wire on either face. Not a smaller wire. No wire.
Light test: Raking light, angled to the edge. Bright line means the edge is rounded there. Dark edge means sharp.
Both checks work in any shop, with no equipment, in thirty seconds. They answer the only question that matters.