Microbevels Explained

A microbevel is the best-value trick in sharpening after the strop. It costs nothing, it works on chisels and plane irons alike, and it turns the slow part of sharpening into the fast part. Once you understand why, you will probably never grind a full flat bevel again.

Primary versus secondary bevel

A freshly ground tool has one bevel: a single flat facet, the full height of the grind, running from the edge back up the blade. Call that the primary bevel. Its whole face is a fair amount of steel.

A microbevel— the secondary bevel — is a tiny additional facet ground right at the cutting edge at a slightly steeper angle, no wider than a pencil line. The primary bevel still does the job of clearing steel behind the edge; the microbevel is the only part that is actually sharpened to a keen edge and the only part that touches the wood.

So the tool now has two angles stacked at the tip: a shallow primary that supports and clears, and a slightly steeper micro-facet that forms the working edge. The angles themselves are the subject of sharpening angles explained; this page is about why splitting them apart is worth the trouble.

Why a microbevel saves time

The saving is pure geometry, and it is large. When you sharpen a full flat bevel, you have to abrade the entire face of that bevel — every square millimeter of it — on every stone, just to move the edge. That is a lot of steel, and at fine grits it is slow.

A microbevel is a sliver. Sharpening it means abrading a facet a fraction of a millimeter wide, so a resharpen touches almost no metal. What took several minutes on the full bevel takes a few strokes. You get the durability of the steeper edge angle and the sharpening speed of a tiny surface, and the finer the stone, the bigger the saving — because polishing a sliver is quick and polishing a whole bevel is not.

There is a second dividend. Because the microbevel is so small, a strop can refresh it in seconds without ever going back to a stone, which is why microbevels and stroppingwork so well together — the strop maintains the exact facet the microbevel created.

Angle stacking

The two angles are chosen so the microbevel sits a little steeper than the primary. A common, sane pairing:

The principle is simple: grind the primary shallow enough to clear steel and keep sharpening fast, then set the microbevel at whatever the job needs for durability. Only the microbevel angle affects how the edge holds up, so that is the number you tune to the work. A degree or two either way makes no practical difference; consistency between sharpenings matters far more, which is exactly what a honing guide delivers.

Setting it in a honing guide

A honing guide makes microbevels trivial and repeatable, which is most of the point. There are two ways to add the steeper facet:

1. Reposition the blade.Grind the primary at your set projection, then pull the blade back a few millimeters in the guide — less projection raises the effective angle — and take a few strokes on your finest stone. The edge now carries a steeper micro-facet.
2. Lift or shim the guide. Slip a thin shim under the roller, or tip the guide up a couple of degrees, for the last few finishing strokes. Some guides have a built-in eccentric roller that does this with a flick.

Either way, the key is repeatability: next time, set the same projection and you land on the same microbevel, so you hone the existing facet rather than grinding a new one. The best honing guides page covers which guides make this setting fast and which fight you.

Back bevels and the ruler trick

Microbevels have a cousin on the flat side of the blade. The back of a chisel or plane iron must be flat and polished right at the edge, but flattening the whole back of a wide iron is slow, tedious work — and on an old or slightly hollow iron it can be nearly impossible.

The ruler trick, associated with David Charlesworth, solves this for plane irons. You lay a thin steel ruler along one long edge of your finest stone and rest the back of the iron across it, which lifts the edge a fraction of a degree off the stone. A few strokes then polish a whisper-thin back bevel at the very edge instead of the entire back. That tiny back bevel meets the microbevel to form the cutting edge, and you have skipped hours of back-flattening.

Two cautions. Keep it to plane irons, not chisels — a chisel is often registered flat on its back to pare, and a back bevel spoils that reference. And keep the back bevel tiny; it slightly raises the effective cutting angle, which is usually harmless but should be deliberate. Used within those limits it is a genuine time saver, and it pairs naturally with the plane-iron procedure in how to sharpen a plane iron.

When to reset the primary bevel

A microbevel is not free forever. Every time you resharpen, the micro-facet gets a touch wider, because you are removing metal from it and it creeps back up the primary. For a while that is invisible. Eventually the microbevel grows wide enough that sharpening it is no longer quick — at which point it has become a small primary bevel and you have lost the speed advantage that was the whole reason for it.

That is the signal to reset: go back to a coarse stone or a coarse diamond plate, regrind the primary bevel at its shallow angle to shrink the micro-facet back to a sliver, and start the cycle again. In practice this happens after many sharpenings, not many sessions — you might regrind a primary a handful of times a year on a well-used tool. If you own a powered grinder or a coarse plate it is a two-minute job; if you do not, it is the one moment a coarse stone earns its place, as set out in sharpening angles explained.