Saw kerf vs yield: what 1 mm costs on a multi-rip line (simple math)

Kerf is the “tax” you pay on every cut. On a multi-rip saw, where you make multiple cuts per board and run high volume, even a small kerf change can translate into measurable m³ over a week.

The key: use real kerf under production conditions, not just the catalog number.

1) What “real kerf” actually includes

Real kerf is not only the plate thickness:

• plate thickness + tooth set / tip width,
• runout and vibration,
• feed stability (board movement widens the cut),
• blade condition and overheating.

That’s why two mills can see different results with “the same” blade model.

2) The formula: convert kerf into volume loss

Simple model (good enough for decisions):

Loss m³ = kerf [m] × thickness [m] × length [m] × number of cuts

For daily production:

Loss m³/day = kerf × thickness × length × (cuts/board) × (boards/day)

Note: if you rip one board into N pieces, you typically make ~N-1 cuts (not counting extra edge trims, depending on your process).

Example (difference in kerf)

Assume:

• kerf reduction: 0.8 mm (4.0 mm → 3.2 mm) = 0.0008 m
• thickness: 25 mm = 0.025 m
• length: 3.0 m
• 4 cuts per board
• 1200 boards/day

0.0008 × 0.025 × 3 × 4 × 1200 = 0.288 m³/day

At 5 production days/week that’s ~1.44 m³/week from kerf alone.

3) When reducing kerf makes sense (and when it’s a trap)

It makes sense when:

• feed is stable (guides, hold-downs, pressure),
• extraction is strong (less heat, better cut quality),
• sharpening discipline is good and repeatable,
• you run high volume with many cuts.

It’s a trap when:

• you try to “save yield” with thin blades while infeed reference is random,
• boards enter shifted or skewed (loss from wane/positioning is often bigger than kerf),
• cut quality drops and you pay in rework, trim, and claims.

In many lines the fastest ROI comes from stabilizing offset + angle before the multi-rip, then optimizing kerf.

4) How to check your kerf under production conditions

• Measure the actual cut width on several boards (not just one).
• Compare across product types: wet/unsteady stock often shows larger kerf in practice.
• Track whether kerf “drifts” by shift: drift often points to feed stability, guides, or blade condition.

5) Related reads (usually bigger levers than kerf alone)

• How to calculate yield properly (log vs stage): /blog/how-to-calculate-sawmill-yield/
• How to reduce wane waste on unedged boards: /blog/reduce-wane-waste-unedged-boards/
• Board positioning before the multi-rip (stable reference): /blog/board-centering-before-multi-rip-saw/

If you want a quick ROI estimate for kerf changes vs positioning/geometry losses on your line, contact us: /contact/.