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Woodworking Math

Learn · 6 min

Reading grain direction

How to tell flatsawn from quartersawn, which way to feed a board so the cutter doesn’t tear it, and why the two kinds of board move differently.

Read the end of the board first

Look at the end grain. On a flatsawn (plainsawn) board the growth rings run roughly along the wide face, often as curves; on a quartersawn board they run roughly at right angles to it. Riftsawn boards are in between.

Two sources: Rockler and USDA Forest Products Laboratory [source 1, source 2]

The two cuts move differently: across a flatsawn face the wood shrinks and swells in its tangential direction, across a quartersawn face in its radial direction, and the Wood Handbook’s tables show tangential shrinkage is the larger for every species. Northern red oak, for example, shrinks 8.6% tangentially and 4.0% radially from green to oven-dry.

One source: USDA Forest Products Laboratory, the authority for the wood properties it measured [source 2]

Feed with the grain

The wood fibres in a face rarely run perfectly parallel to it. Cut so the knives run with the fibres and they shear off cleanly; cut against them and the knives lift the fibres ahead of the cut and tear them out.

3 sources agree [source 1, source 3, source 4]

To read the slope, look at the edge next to the face you are about to plane: the grain lines there show which way the fibres rise toward that face. Mark the feed direction on the board before you start.

Two sources: Rockler and Popular Woodworking [source 1, source 3]

Reading grain is a good guess, not a certainty. Take a light first cut; if it tears out, turn the board end for end and try the other way.

Two sources: Rockler and KM Tools [source 1, source 5]

Reversing grain can surprise even an experienced woodworker and tear out whichever way the board goes, leaving work for a scraper or sandpaper.

Two sources: Rockler and Popular Woodworking [source 1, source 3]

Put it to work

Check yourself

  1. 1. Which way should a board go into the jointer or planer?

  2. 2. Your first light pass tears out. What should you try next?

  3. 3. On a quartersawn board, how do the growth rings run on the end grain?

  4. 4. Per the Wood Handbook, how much does northern red oak shrink from green to oven-dry?

0 of 4 answered

Sources

  1. Rockler, Avoid tearout by reading the grain, read 2026-11-07
  2. USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282, 2021), ch. 4 Table 4-3 (shrinkage) and ch. 13 (dimensional change), read 2026-11-07
  3. Popular Woodworking, Reading grain direction, read 2026-11-07
  4. Woodcraft, How to mill rough lumber: dressing stock for woodworking, read 2026-11-07
  5. KM Tools, A newbie’s guide to reading grain direction and avoiding tearout, read 2026-11-07

How sources are counted and labelled: how we source these numbers.