When a blade comes back from sharpening, most shops check one thing: does it feel sharp? Run a fingernail across the tooth. If it catches, it’s sharp.
That’s not wrong. But it’s about 10% of the information that actually matters.
Blade geometry is what determines cut quality, material compatibility, and wear rate. A blade sharpened to the wrong geometry — even if technically sharp — will underperform, cause tearout, or wear out faster than it should.
Here’s what you need to know.
Hook Angle (Rake Angle)
Hook angle is the angle at which the tooth face meets the vertical. It’s one of the most important specs on a blade.
Positive hook (5°–20°): The tooth leans forward. More aggressive bite. Pulls the material through. Best for ripping solid wood — faster feed, more efficient material removal. Downside: more tearout on the exit face, more prone to grabbing.
Negative hook (-2° to -10°): The tooth leans back. Less bite, more scraping action. Safer for crosscutting, better for miter saws and radial arm saws where blade deflection and kickback are concerns. Also better for aluminum and melamine where aggressive bite causes chipping.
Neutral hook (0°): A compromise. Used in general-purpose blades.
What goes wrong: A sharpening shop that doesn’t document your blade’s original hook angle will grind it to their standard. A 15° positive hook blade might come back at 8°. It still cuts, but you’ll notice it feels “different” — more resistance on rips, less smooth on the pull. That’s the geometry change, not a sharpening quality problem.
Tooth Geometry: ATB, FTG, TCG, HATB
Alternate Top Bevel (ATB): Alternating teeth are ground at an angle — typically 10°–20° — in opposite directions. Creates a scoring action on the kerf walls. Best general-purpose grind for crosscuts and plywood. The bevel angle determines aggressiveness: higher bevel = cleaner veneer cut, faster wear.
Flat Top Grind (FTG): All teeth ground flat. No bevel. Maximum material removal per tooth pass. Best for ripping solid wood where speed matters and face quality is less critical. Rough edge requires jointing or sanding.
Triple Chip Grind (TCG): Alternating flat teeth and chamfered “raker” teeth. The raker opens the kerf, the flat tooth cleans the bottom. Excellent for melamine, plastics, and non-ferrous metals. Very wear-resistant.
High ATB (HATB): ATB with bevel angles of 25°–40°. Extreme scoring action. Best for cross-cutting hardwoods and veneer work where surface quality is paramount. Wears faster than standard ATB; needs more frequent sharpening.
Clearance Angle
The clearance angle (back relief) is the angle behind the cutting edge that prevents the tooth body from rubbing the kerf wall. Too small = friction and heat. Too large = weakened tooth structure prone to chipping.
Most carbide blades use 10°–15° clearance. This is rarely changed in sharpening, but incorrect clearance is a common sign of poor grinding — and it shows up as burning on rip cuts with no obvious cause.
Kerf Width
Blade kerf isn’t a sharpening spec, but it’s worth understanding. Full-kerf blades (¹/₈”) are standard for table saws with sufficient motor power. Thin-kerf (³/₃₂”) reduces material waste and is appropriate for lower-powered saws.
Don’t sharpen a thin-kerf blade at a shop that assumes full-kerf — they may add material to both sides and widen your kerf, creating fit problems.
The Spec Sheet Solution
Every blade should have a documented spec sheet with:
- Hook angle
- Tooth grind type
- Bevel angle
- Clearance angle
- Kerf width
- Intended material
When a blade goes out for sharpening, this spec sheet goes with it. When it comes back, those specs are verified.
Most shops have no spec sheets for their blades. They rely on the sharpening shop to “sharpen it back to how it was” — which is impossible if no one wrote down what it was.
Every blade in the Ciklek program has a documented spec sheet. Sharpen to spec, every time, with before/after verification. That’s what correct sharpening looks like.