Sharpen a Silky Gomboy 240 Pruning Saw with a Feather Edge File in Six Passes

Where the Chrome Argument Breaks Down

The Gomboy 240 uses impulse-hardened teeth. Silky hardens a narrow zone at each tooth point, leaving the tooth body around 45 HRC and the point closer to 62 HRC. Over that hardened zone sits hard-chrome plating, a low-friction coating roughly 3 to 5 microns thick.

That coating survives longest on the flanks. At the extreme cutting point, use does the damage first. Green apple, pear, and especially dry fruit wood polish through the chrome at the tips, then the exposed hardened steel rounds over. Once that happens, the blanket claim that the saw can never meet a file falls apart. A feather edge file, the fine double-cut diamond-and-steel type sold for touch-up work, can cut the exposed steel at the point while leaving the plated flanks mostly alone.

Contact area is the practical limit. The job concerns perhaps 0.2 mm of rounded point per tooth on a blade with 15 teeth per 30 mm. A feather edge file removes material in the tens of microns per stroke, so controlled light passes change the point before they change the whole tooth form.

The Six-Pass Sequence

Open the blade fully, lock the pivot, and clamp the saw in a vise. Keep the tooth line about 20 mm above soft wooden jaw pads so the blade does not flex or ring while you work.

The Gomboy 240 tooth line uses a four-retooth pattern: three cutting teeth followed by a raker-style clearance tooth, all arranged for the pull stroke. File the pull-stroke faces only. Match the gullet angle already on the saw, roughly 60 degrees to the blade spine.

For the first two passes, place the feather edge file flat against the front bevel of each cutting tooth. Move in one direction and lift the file on the return. Use light pressure. The cleanest reference is usually mid-blade, where the teeth wear slowest and hold the factory angle longest.

For passes three and four, work the opposing bevel on the teeth that have it. Keep the same relationship to the blade spine. The pressure should feel closer to drawing than grinding; the file should cut the worn tip, then leave the tooth shape alone.

Pass five is a single unloaded trip along the full tooth line to reduce any raised burr. Pass six is a deburring wipe drawn along the flat of each side with the file almost parallel to the blade face.

The six-pass description refers to the whole working section. In practice, the file touches many teeth during that circuit, with only a few light strokes reaching any single point. Overworking is the common failure. Each added cut after the tooth tip catches a thumbnail removes hardened steel that cannot be put back, and impulse hardening has limited depth. When the tip drags on a fingernail edge, the filing is finished.

Angle matters more than force. A feather edge file held at 55 degrees against a factory grind near 60 degrees slowly reprofiles the tooth line across repeated sharpenings. Once the tooth form changes enough, the saw starts to pack its gullets in green wood and stops clearing sawdust cleanly. Reading the mid-blade teeth before each session keeps the reference on the saw itself.

What the Saw Feels Like on Live Wood

A touched-up Gomboy 240 should crosscut a 40 mm green apple limb with the saw’s own weight doing most of the loading. When the same limb asks for heavy downward pressure and the cut slows sharply, the saw is often dull rather than undersized for the branch.

That feel test is worth trusting because the failure mode of the six-pass method is subtle. A tooth line reprofiled a few degrees off will still bite; it just stops shedding chips and drags. The weight-only crosscut is the earliest sign that the geometry is still intact, before any of it shows in the cut face.

It also explains why pruner-style honing pressure has no place on this blade. A carbide sharpener carrying two or three light strokes belongs on a single-bevel bypass edge, where the whole point is to hone one continuous edge back to keen. A Felco blade, for instance, sits on a 23-degree bevel and takes that treatment well. The Gomboy has a set tooth line instead, and the same heavy hand rolls the impulse-hardened points and wrecks the geometry the six-pass method exists to preserve.

Storage After Filing

Hard-chrome plating resists rust wherever the coating remains intact. Freshly filed tooth tips are bare steel as soon as the file leaves them. A wipe of camellia oil, the traditional dressing for Japanese blade steel, protects those exposed points from the flash oxidation that can pit a filed edge within a week in humid storage. Two drops worked along the 240 mm blade covers the tooth line.

The pivot deserves the same treatment. A Gomboy 240 that folds stiffly usually has grit in the pivot washer. Forcing the handle open loads the blade base laterally, and over months that can introduce a slight set that tooth filing cannot correct.

Flush the pivot with a small shot of the same oil, work the saw open and closed twenty times, and wipe away the excess. With the lock released, the blade should fall open under its own weight.

When the Blade Has Given Enough

The six-pass method has a hard limit in the impulse-hardened zone. Each filing removes hardened material from an area Silky measures in fractions of a millimetre. After four or five full sharpening sessions on a heavily used blade, the file reaches the softer tooth body under the hardened point. From there, the edge can dull in a single afternoon of pear pruning no matter how carefully the angle is held.

The economics are plain. A replacement Gomboy 240 blade costs less than a complete saw, and the swap at the pivot is a single-screw job. The feather edge file can extend a blade’s working life across two or three seasons it would otherwise lose, then the blade earns its retirement.

What the file cannot restore is the induction-heating flash that put the hard zone there in the first place. That leaves an open question every time you clamp a well-used blade in the vise: whether the tip you are dressing still sits in hardened steel, or whether the file has already crossed into the soft body underneath and you are simply postponing the swap.