Reading the surface
A single raised line running the length of the board is a nick in one knife. Move that knife sideways a millimeter and the line disappears.
A regular ripple is a setting problem — one knife projecting further than the others, taking the whole cut.
Burnishing and burning with no tear-out is dullness.
Tear-out on figured grain only is not dullness at all; it is what straight knives do to reversing grain, and only a helical head fixes it.
Always as a matched set
A new knife next to a worn one sits at a different cutting circle, takes the entire cut alone, dulls at several times the rate, and leaves the ripple people mistake for a bearing fault.
The upgrade that ends this page
A helical cutterhead with indexed carbide inserts: rotate an insert when it dulls, no gauge, no set, and no tear-out on figured grain.
This does not replace your machine’s manual. Guards, riving knives and safe working procedures differ between machines, and the manufacturer’s instructions for yours take precedence over anything written here.
What comes up most often
Can I sharpen planer knives myself?
HSS knives can be reground, and doing it accurately needs a jig — the bevel and the length must match across the set. Disposable double-edged knives cannot; you flip them and then replace them.
Last reviewed 2026-08-12
