Why is my hand plane tearing chunks out of the wood?
Tear-out is a grain-direction problem before it is anything else. How to read the grain, and the five adjustments that deal with timber where no direction works.
- Difficulty
- intermediate
- Time
- 20 min
- Read
- 4 min
Short answer
You are planing uphill into the grain, so the blade is lifting the fibres before it cuts them. Look at the edge of the board, find which way the grain slopes, and plane downhill — the same sense as stroking a cat with the fur. If the grain reverses part way along, take a much finer shaving, set the cap iron very close to the edge, close the mouth up, skew the plane, and sharpen.
Wood fibres run in a direction, and they are only supported from one side. Cut them where they are supported and they shear cleanly. Get under them and they split ahead of the blade and tear out in a chunk, leaving a pit that goes deeper than the shaving you were trying to take. Everything below is a way of stopping the blade getting underneath the fibres.
Step by step
- Read the grain on the edge of the board.Look at the lines on the edge, not the face. They run diagonally, and one direction has them rising towards the surface you are planing while the other has them running down into it. Plane in the direction they slope downwards — the fibres are then supported from beneath as the blade meets them.
- Reverse and take a test shaving.If the surface tears, turn the board round and plane the other way. In most straight-grained timber this alone solves it, and it takes ten seconds to test.
- Take a finer shaving.The thicker the shaving, the further ahead of the blade the split runs and the deeper the tear. Wind the blade back so the shaving is translucent. A fine cut tears far less even in difficult grain.
- Set the cap iron very close to the edge.On a bevel-down bench plane, this is the most powerful anti-tear-out adjustment there is and the most neglected. Move the cap iron so its leading edge sits a fraction of a millimetre behind the cutting edge. It bends the shaving sharply upwards as it forms, which breaks the split before it can run ahead.
- Close the mouth.Move the frog forward so the gap ahead of the blade is narrow. The front of the mouth then presses the fibres down immediately in front of the cut and prevents them lifting. A tight mouth needs a fine shaving, and the two go together.
- Skew the plane.Turning the plane so the blade meets the timber at an angle lowers the effective cutting angle and slices rather than chops. It is the traditional answer to awkward grain and costs nothing to try.
- Sharpen.A blunt edge compresses fibres before it severs them, which lifts them, which tears. A tool that suddenly starts tearing on timber it was handling fine ten minutes ago has gone blunt.
- For reversing or figured grain, change the cutting angle.A higher effective cutting angle scrapes rather than slices and greatly reduces tear-out. On a bevel-up plane, hone the blade at a steeper angle. On a bevel-down plane, add a small back bevel to the blade, or fit a high-angle frog.
- Know when to stop planing and start scraping.Some timber — burr, wild figure, curly grain — will tear whatever you do. A card scraper cuts with a burr at a very high angle and produces a clean surface on exactly the timber that defeats a plane.
Tips
- On a board where the grain reverses, plane each half in its own direction and meet in the middle rather than trying to take one full-length shaving.
- Tear-out is far worse in softwood around knots, because the grain swirls. Approach a knot from several directions, lightly.
- Sanding does not remove tear-out — it just rounds the edges of the pits and makes them harder to see until a finish goes on.
- Damp the surface lightly and let it dry before the final passes on difficult timber. Slightly raised, stiffened fibres cut more cleanly.
Questions people ask
How do I tell which way the grain runs on a planed board?
Look at the edge for the diagonal lines, or run a thumbnail along the face in both directions — one feels smooth and one catches slightly. The smooth direction is the direction to plane.
Does this apply to power planers and routers too?
Yes, exactly the same physics. A router leaves tear-out for the same reason, which is why the standard fix there is a light final pass and, on figured timber, a whisper-light climb cut to score the fibres first.
What is a back bevel?
A very small bevel honed on the back of a bevel-down plane blade, which raises the effective cutting angle. A degree or two makes a real difference on difficult grain, and it is easily done with a thin ruler under the blade on the stone.