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A plane blade should be checked for nicks before you put it on a honing stone. A nick is a local chip or low spot in the cutting edge. If you start honing without finding it, you may waste time polishing the rest of the edge while the damaged area remains. Worse, a large nick can make you remove far more steel than necessary.
The inspection takes a few minutes and needs only good lighting, a clean surface, and something that lets you see the edge clearly. For routine work, a bright bench light and a small magnifier are enough. A 10x illuminated loupe is useful if your eyesight is not sharp, but it is not essential.
Clean and Prepare the Blade
Remove the blade from the plane and wipe away resin, dust, and honing oil. Dirt can hide a small chip or make the edge look uneven. Use a rag and mineral spirits for oily grime, then dry the blade completely. Avoid holding the cutting edge with your fingers; grip the sides or the thick back of the blade.
Place the blade on a flat, clean surface with the bevel facing up. A piece of white paper under the blade makes dark defects easier to see. If the blade is rusty, remove loose rust first. Do not mistake surface pitting behind the edge for a nick in the edge itself.
Use Light to Find Damage
Hold the blade so the bevel faces a strong light source. A sharp edge normally reflects very little light when viewed straight on. A nick creates a bright point or short bright line because its damaged area is no longer a clean, continuous edge.
Rock the blade slowly from side to side. Inspect the full width, including both corners. Check from several angles rather than relying on one view. A reflection can disappear when the blade moves only a few degrees, and a shallow defect may show on one side but not another.
Look for these signs:
- Bright dots or gaps: usually small chips or dents in the cutting edge.
- A repeating scalloped edge: often caused by a coarse grinding wheel or uneven sharpening.
- A rolled or wire edge: a thin strip of steel bent over the tip, rather than missing steel.
- Dark pits at the edge: corrosion that may break through once you sharpen past it.
- Uneven corners: a corner projecting farther than the middle, which can leave tracks in the work.
Check the Edge Without Cutting Yourself
Do not drag a fingertip across the edge. Instead, lightly move a fingernail from the back of the blade toward the edge, perpendicular to it, in several places. A clean edge feels continuous. A nick may catch the nail, while a wire edge can feel like a thin hook or burr.
Use very light pressure. This test is for confirming what you saw, not for testing sharpness aggressively. Test the left corner, center, and right corner separately. On a typical 50 mm (2 inch) plane blade, make at least five checks across the edge so a small defect is not missed.
A straightedge can also reveal a large hollow or high spot. Hold a small steel ruler against the cutting edge and look for light underneath. This does not replace visual inspection, because a nick can be too small to show against a ruler.
Measure the Nick Before Honing
Estimate the defect’s width and depth. A 0.25 mm nick may disappear with ordinary honing, while a 1 mm or deeper chip can require grinding or considerable work on a coarse stone. The important measurement is how far the damage reaches back from the edge, not just how wide it looks from above.
| Damage | What it looks like | Best response | Main trade-off |
|---|---|---|---|
| Small nick, under 0.25 mm | One or two tiny bright spots | Hone normally, then inspect again | Several extra strokes may be needed |
| Moderate nick, 0.25–1 mm | Visible notch that catches a nail | Use a coarse stone or grinder carefully, then hone | More steel removal and a wider bevel |
| Large chip, over 1 mm | Clear missing section or broken corner | Grind back past the damage, or replace the blade | Grinding can overheat and shorten the blade |
| Wire edge | Thin flap rolled to one side | Remove with light honing or a few back strokes | Heavy pressure can create another burr |
Choose Between Honing, Grinding, and Replacement
For a tiny nick, start with your normal honing setup. A 1,000-grit stone can establish a clean edge, followed by a finer stone around 4,000 to 8,000 grit if you need a polished edge. Use consistent pressure and inspect after 10 to 15 strokes. If the bright spot is shrinking, continue. If the rest of the edge is polished but the nick remains, switch to a coarser abrasive rather than spending an hour on the fine stone.
For a deeper nick, a coarse 220-grit waterstone can remove steel with less risk than a power grinder. It is slower, but overheating is not a concern. A bench grinder is faster for major damage, yet the edge can turn blue in seconds if you press too hard or linger in one spot. Blue steel has been overheated and may no longer hold an edge properly.
If the nick reaches more than roughly 2 mm into a thin blade, or the blade has already become noticeably shorter from repeated repairs, replacement can be sensible. A compatible replacement plane blade is often cheaper than the time spent reshaping a badly damaged one. For an inexpensive plane, the cheaper blade may be adequate; for a high-quality or vintage plane, preserving the original blade can justify slower abrasive work.
Inspect After the First Honing Pass
After the first abrasive, wipe the blade clean and repeat the light test. The edge should show an even, narrow strip of fresh steel. Any isolated bright crescent or notch means the damage is still present. Do not move to a finer stone until the edge is continuous from corner to corner.
Finish by checking the blade in the plane. Set the cutting edge for a very light cut and take a shaving from scrap wood. If the plane leaves a groove at one side, check for a projecting corner or uneven camber rather than assuming the blade is dull. A replacement plane blade is worth considering when repeated nick repairs have left the edge badly out of shape.
For future checks, store the blade so it cannot contact screws, chisels, or other steel tools. Most new nicks come from dropping a blade, setting it on a dirty bench, or striking the edge against the plane body during assembly—not from normal planing.