A chainsaw cutter and its depth gauge (raker) work as one system — file the tooth without resetting the raker gap to 0.025", and the cutter will eventually sit level with or below the raker, stalling the cut. Use a progressive depth gauge tool every third or fourth sharpen to keep the two in balance as the tooth wears back.
In professional forestry, a chainsaw is only as efficient as its cutting edge. A saw engine produces horsepower; the chain converts that horsepower into work. If the cutter geometry is compromised, horsepower is converted into waste heat and vibration, not wood chips.
Correct hand-filing is not merely about making the edge "sharp." It is about restoring the factory geometry of the cutter — and that means two things working together: the cutter itself, and the depth gauge that governs how deeply it bites. Get one right and neglect the other and the saw still won't cut.
This guide covers both. For the quick field version, see our how to hand file a chainsaw guide; what follows is the advanced protocol.
The Hand Plane Analogy
To understand a chainsaw cutter, view it as a miniaturised woodworking hand plane:
The cutter (tooth): the blade of the plane. It severs the fibre.
The depth gauge (raker): the sole of the plane. It controls how deep the blade is allowed to bite.
The vertical distance between the top of the raker and the top of the cutter is the depth gauge setting. On a standard chain, that gap is 0.025 inches (0.64mm).
If the gap is zero: the cutter skids across the wood like a bald tyre on ice. You get fine dust and friction heat.
If the gap is correct: the raker rides on the wood, allowing the cutter to take a controlled 0.025" bite. You get thick, square chips.
1. File Position: The Structural Integrity Rule
The most common error in hand filing is incorrect vertical height. The file should be positioned so that 20% (one-fifth) of the file diameter protrudes above the top plate of the cutter.
Correct height: creates a durable, C-shaped side plate profile with adequate metal support under the top plate.
Too low: creates a "hook" or "beak." The edge becomes too thin and is prone to tensile failure (snapping).
Too high: creates a "back-slope." The cutter will slide over the wood without engaging (feed failure).
Critical Nuance: Full Chisel vs. Semi-Chisel
Semi-chisel (rounded corner): the chamfered profile is structurally forgiving. A slight deviation in file height will reduce cutting speed but rarely compromise the tooth's structural integrity.
Full chisel (square corner): this profile has zero tolerance for error. If the file sits too low, the extremely fine square point becomes structurally unsupported. In dense Australian hardwood, that unsupported tip will not just dull — it will micro-fracture or snap off entirely. When filing full chisel, be obsessive about the 20% high file position. (More on the trade-off in our full chisel vs semi-chisel guide.)
2. The Stroke (Kinematics)
The filing action must be deliberate and consistent to maintain these angles.
Direction: file from the inside of the cutter to the outside only. Never drag the file backward.
Pressure: apply firm, steady pressure against the working corner (back and up).
Rotation: as you push, impart a slight rolling motion to the file. This clears filings from the file teeth and produces a smoother finish on the chrome plating.
Consistency: if the master cutter (the shortest tooth) required 4 strokes to restore the edge, apply exactly 4 strokes to every subsequent cutter to maintain balance.
Matching the right file to your chain pitch is step zero — see our chainsaw file guide for the sizing chart.
3. Depth Gauges: Mastering the 0.025" Gap
Restoring the cutter edge is only half the process. Here is the physics trap that catches the amateur.
The Geometry of Wear
A chainsaw cutter is not flat; it is sloped. The top plate angles downward from front to back to provide clearance. Every time you sharpen, you file the face of the cutter back — and because of that slope, as the face moves back, the height of the tooth drops.
The consequence: if you sharpen the cutter but do not lower the raker, the cutter eventually sits lower than the raker. The gap closes. The chain stops cutting. You cannot simply sharpen the teeth; you must mechanically re-balance the relationship between cutter and raker.
The Danger Zone: Why Freehand Is Forbidden
Some old-school fallers will tell you to take a flat file and knock the rakers down by eye. Do not do this.
If you file a raker too low (say, creating a 0.050" gap), you turn your chainsaw into an uncontrolled machine. When the tooth enters the wood it bites too deep to sever the fibre. It stalls the chain or, far worse, catches violently and transfers that energy into the bar. Excessive depth gauge settings are the primary mechanical cause of kickback.
The "Aggressive" Trap
Because full chisel cutters sever fibre more efficiently than semi-chisel, they inherently feed faster. This leads to a common error: operators lower full chisel depth gauges to .030"+ hoping for maximum speed.
Do not do this in hardwood. The square corner grabs fibre violently. If the raker is too low, the saw will "snatch" rather than cut. This spikes the load on the crankshaft, increases kickback risk, and causes catastrophic cutter breakage. We strictly recommend adhering to the .025" factory spec for chains running in dry or dirty timber.
The Solution: The Progressive Mandate
Standard "flat plate" gauges are adequate for new chains, but they are static — they don't account for the changing geometry of the tooth as it wears. We mandate a progressive depth gauge tool, which sits across the top of the cutters, reads the current tooth length, and calculates exactly how much height to remove from the raker to maintain the correct attack angle.
The protocol:
Sharpen your cutters first, using the file position and stroke above.
Place the progressive tool over the chain.
If the raker protrudes through the slot, file it flush with the tool using a flat file.
This resets the 0.025" gap relative to the new height of your worn cutter.
Frequency: check your rakers every third or fourth sharpen. If you haven't touched them in three sharpenings, your saw is running at roughly half its potential.
The Verdict
If you are leaning on your saw, forcing it to cut, you are doing it wrong. A properly tuned chain feeds itself.
A chain maintained to these specifications will cut with the efficiency of a new factory loop. Deviating from these angles results in heat build-up, excessive engine load, and operator fatigue.
Maintain the geometry. Control the gap. Control the cut.
And when a chain is filed past its service life — past the witness mark, or rock-damaged beyond a touch-up — replace it with one matched exactly to your saw. Search by Bar Stamp, or Search by Chainsaw.
Depth Gauges and Hand-Filing — FAQ
What is the correct depth gauge setting on a chainsaw chain?
0.025 inches (0.64mm) below the cutter tip on a standard chain. This gap controls how deep the tooth bites; too shallow and the chain skids, too deep and it grabs violently.
Why does my chain stop cutting well even though I keep sharpening it?
Every sharpen files the cutter face back, and because the top plate slopes, the tooth height drops slightly each time. If the raker isn't lowered to match, the gap closes and the chain eventually stops biting no matter how sharp the edge is.
Can I lower depth gauges by eye with a flat file?
It's not recommended. An uneven or excessive gap is the primary mechanical cause of kickback. A progressive depth gauge tool reads the current tooth length and sets the correct height automatically.
How often should I check my depth gauges?
Every third or fourth sharpen. Going longer without checking typically means the saw is cutting at roughly half its potential.
Need the right chain for your saw?
Don't guess — match it exactly. Read the pitch, gauge and drive-link count off your bar and we'll find your precise chain, or search by your saw model. Every chain is backed by our Guaranteed Fit promise, checked against your bar stamp before it ships.