Edging is where a strimmer earns its name as a finishing tool rather than a brute-force grass cutter. Done well, it leaves a sharp, professional-looking line between lawn and path or bed with almost no visible damage; done badly, it scalps the turf, sprays gravel across the patio, and leaves a ragged fringe that looks worse than if you’d left it alone.
Setting up the head for edging mode
Most trimmer heads with a straight or split shaft can rotate roughly 90 degrees from the horizontal cutting position to a vertical one. Before you do anything else:
- Stop the engine (or remove the battery on cordless models) and check your manual for whether your gearbox is rated for extended vertical running - some budget gearboxes rely on grease pooling in a particular orientation and can run dry if tipped vertical for long spells.
- Loosen the head-angle adjustment collar or bolt, usually found where the shaft meets the gearbox housing.
- Rotate the head so the cutting plane is vertical, with the line spinning in a plane parallel to the edge you’re cutting rather than parallel to the ground.
- Re-tighten the adjustment collar firmly - a head that shifts mid-cut is both dangerous and impossible to control accurately.
Safety note: Rotating the head brings the spinning line and the guard much closer to your legs and feet than normal mowing work. Wear sturdy boots, not trainers, and keep your leading foot well back from the line’s arc before you squeeze the throttle.
Getting the angle right
The goal is a shallow vertical face, not a trench. Hold the shaft so the line spins in a plane that’s close to vertical but tilted slightly - typically 5-15 degrees off true vertical, with the bottom of the arc angled very slightly under the lawn edge rather than straight down. This slight undercut:
- lets the line shear the grass cleanly at the point where turf meets path
- stops the tip digging straight down into soil and throwing dirt
- produces a clean vertical “wall” on the lawn side rather than a rounded, torn edge
Holding the head too flat (close to horizontal) turns edging into ordinary strimming and won’t create a defined line. Holding it too steep, with the tip driving straight into the ground, is what causes scalping and soil throw.
Working direction and technique
- Start at one end of the border and walk it steadily rather than lunging in short bursts - a constant walking pace gives an even cut depth along the whole run.
- Work with the line tip leading, using only the last 2-3 cm of line to make contact, not the full swept arc. The tip is where line speed and cutting effectiveness are highest.
- Move in the direction that throws clippings and debris onto the lawn side, not onto the path, patio, or road. On a typical clockwise-spinning head this usually means walking so the cutting side of the head is on your left, with debris discharging to your right and rearward onto the grass.
- Make a single pass at the correct depth rather than repeated deep jabs - re-passing over the same 10-15 mm groove to tidy stragglers is fine, but don’t try to remove a large lip of turf in one go.
- For an established, overgrown edge with a build-up of thatch or a raised lawn lip, take it down gradually over two or three passes rather than trying to cut the full height in one go - the line will bog down and the cut will be ragged.
Creating a clean gully along paths and beds
A “gully” is the small, defined vertical channel between the lawn and a hard edge (path, patio, driveway) or a soft edge (flower bed). To create and maintain one:
| Edge type | Target cut | Common mistake |
|---|---|---|
| Lawn-to-path (hard edge) | Shallow vertical face, 10-15 mm deep, flush with path surface | Angling the head so it hits the path and throws grit/stone |
| Lawn-to-bed (soil/mulch edge) | Vertical face just proud of the soil line, avoiding bare earth | Cutting into the soil itself, throwing dirt onto the lawn |
| Lawn-to-fence or wall base | Vertical face 5-10 cm off the structure | Running the line directly against masonry, wearing line out fast and pitting soft mortar |
Once a gully is established, maintenance edging is much quicker - you’re only trimming regrowth back to the existing channel, not cutting new turf, so you can walk faster and use a lighter touch.
Safety note: Near hard edges - paved paths, patios, driveways, walls - line and (especially) blade contact will throw debris and can wear line abnormally fast. Keep the guard’s deflector edge angled so debris is thrown down and away from you, and never edge toward bystanders, parked cars, or windows within the 15 m safety zone.
Avoiding scalping and stone throwing
Scalping - cutting so low or so steep that you strip grass down to bare, brown soil - and stone throwing are the two most common edging mistakes, and both come from the same root cause: too much depth, too much speed, or both.
To avoid them:
- Keep the cutting angle shallow (5-15 degrees off vertical) rather than driving the tip straight down.
- Slow your walking pace on any edge bordering gravel, loose chippings, or bare soil - these surfaces throw debris far more readily than solid turf.
- Drop the throttle slightly on gravel or loose-surface edges; you lose a little cutting speed but gain a lot of control over where debris goes.
- If you hit a stone or a hard obstruction and hear the tell-tale crack of line snapping, stop, let the head come to rest, and check the guard and your surroundings before continuing - a stone kicked back at speed can travel several metres.
- Never edge with a metal blade fitted unless the machine and blade are specifically rated for edging use - blades throw debris with far more energy than line and are much less forgiving of a mistimed angle.
Guard position and why it matters here
The guard’s deflector edge is designed to throw debris away from the operator when the head is used in its normal horizontal orientation - when you rotate the head for edging, the guard rotates with it, but its protective geometry is no longer aligned the same way relative to your body.
- Always keep the deflector edge of the guard between the spinning line and your legs, not facing away from you.
- Never remove or trim down the guard to “see the edge better” - this is one of the most common shortcuts that leads to stone-strike injuries.
- If your machine has a small clip-on edging guard or edging shoe accessory, fit it - it’s designed specifically to ride along the path or bed edge and keep cutting depth consistent.
Tidy finish tips
- Do the edges first, then mow or strim the open lawn area - this lets loose clippings from edging fall onto grass you’re about to cut anyway, rather than needing a separate clean-up pass.
- Blow or sweep clippings off hard surfaces once you’re done; damp grass clippings left on paving stain quickly and get slippery.
- For a genuinely crisp finished look, follow up an edging pass with a half-moon edging iron or spade every few weeks to keep the gully’s hard shoulder well-defined - a strimmer maintains an edge beautifully but doesn’t reshape a badly overgrown or collapsed one on its own.
- Check line length before starting a long edging run; edging chews through line faster than open-field cutting because the tip is doing concentrated, repeated work at one contact point. Carry spare pre-wound spools for anything beyond a small garden.
Quick checklist
- Head rotated and locked at roughly 90 degrees, confirmed tight before starting
- Cutting angle 5-15 degrees off vertical, tip leading, not driving straight down
- Walking pace steady, single pass at 10-15 mm depth
- Guard deflector edge facing toward you, away from bystanders and glass
- Slower speed and lower throttle near gravel, loose stone, or bare soil
- Fresh line fitted before a long edging session
When to call a dealer
If the head won’t hold its angle once tightened - slipping back to horizontal under vibration - the adjustment collar or its locking mechanism is likely worn and is a straightforward parts repair for a small-engine shop. If the gearbox feels notably hotter than usual after extended vertical edging work, or you notice grease weeping from the seal, get it checked before it runs dry and damages the bearings; that’s a cheap grease top-up if caught early and a full gearbox replacement if ignored.