Saw Blade Selection
Use section shape, teeth in the cut, tooth form, set, and blade material to narrow the choice before consulting the maker's chart.
Pitch spaces the teeth; gullets carry the chips
Pitch spaces the teeth; gullets carry the chips
TPI means teeth per inch along the blade. A higher TPI is a finer pitch. For evenly spaced teeth, pitch in inches is 1 ÷ TPI. The gullet is the hollow between teeth that provides chip space. Set is the sideways displacement of teeth, making clearance for the blade body in the kerf.
Estimate teeth in the cut before choosing TPI
Estimate teeth in the cut before choosing TPI
As a rule of thumb, aim to keep at least about three teeth engaged. For a uniform pitch crossing one continuous thickness of material:
Estimated teeth engaged = contact length in inches × TPI
Minimum TPI for three teeth = 3 ÷ contact length in inches
Use thickness measured along the tooth line through solid material, not automatically the height of the part. For 0.25 in of continuous contact at 12 TPI, the estimate is 0.25 × 12 = 3 teeth. At the same thickness, the three-tooth calculation gives 3 ÷ 0.25 = 12 TPI.
A calculated minimum is a screening value, not a blade specification. If it falls between available pitches, select a suitable finer option from the maker's chart rather than rounding down. Excessively fine teeth can run out of chip space in thick stock.
Why the answer can be a fraction of a tooth
The product counts tooth spacings across the contact length. Actual engaged tooth tips are discrete, and the number changes as the blade moves. Entry, exit, variable pitch, and curved sections also change contact. This estimate explains the selection principle; it does not guarantee a fixed count throughout a real cut.
Predict first: at mid-depth in the thin-wall tube below, would doubling TPI halve, double, or leave the estimated engagement unchanged? It doubles: the same contact length contains twice as many tooth spacings.
Dashed line = about three teeth; shading = below three. Each plot uses its own vertical scale.
Thin-wall tube, coarse blade
50.80 mm outside diameter; 1.00 mm wall; 6 TPI.
At depth 25.40 mm: 0.47 teeth across 2.00 mm of material.
Across the cut: minimum 0.00; maximum 3.33 teeth.
Below the common rule of thumb of about three teeth.
Contact tends to zero at entry and exit. At mid-depth only the two walls count. The peaks occur where the blade touches the inside circle.
Thick solid bar, fine blade
50.80 mm contact thickness; 25.40 mm feed height; 24 TPI.
At depth 12.70 mm: 48.00 teeth across 50.80 mm of material.
Across the cut: minimum 48.00; maximum 48.00 teeth.
At or above about three teeth here; this is not a blade approval.
Gullets may fill with chips; check the blade maker's guidance.
Estimated teeth = solid contact length ÷ tooth spacing; mm per tooth = 25.4 ÷ TPI. Readouts round to two decimal places; calculations keep the unrounded, real-valued estimate. Highlighted tooth tips illustrate one blade position, not a guaranteed integer count.
Round-section minima include the exact entry and exit tangencies, where contact is zero. A flat bar has constant contact through its feed height, including the limiting faces. Rotate the flat bar 90° to swap contact thickness and feed height; rotating a round bar or round tube about its axis changes neither. This model is a straight tooth line crossing an ideal section, with uniform pitch and no blade tilt.
The thick-bar, fine-blade preset highlights the full contact region as a reminder: gullets may fill with chips; check the blade maker's guidance. It sets no numeric upper limit. Tooth count alone cannot predict chip filling. For shop practice and hazards, see Cutoff Sawing and Safety collection.