Circular marks left by a floor edger are one of the most frustrating — and common — mistakes in DIY floor sanding. The good news is they are almost always preventable with the right grit sequence, movement technique, and a bit of patience before you apply your finish.
Why Edgers Leave Circular Marks
A drum edger spins a sanding disc in a circular motion at high speed. Because it cuts aggressively in all directions, it leaves a pattern of arcing scratches in the timber. These scratches are often invisible under sawdust but become glaringly obvious once a coat of oil, stain, or polyurethane goes on. The marks appear because:
- The disc scratches across the grain as well as with it
- The grit used was too coarse and not followed up with finer grits
- The edger was held stationary for even a moment too long
- The transition zone between the edger and the main drum sander was not blended properly
The Right Grit Sequence
Using the correct sequence of grits is the single most important factor. Never jump straight to a fine grit — you need coarser grits to remove old finish and level the floor, then progressively finer grits to erase the scratches left by each previous pass.
A typical sequence for a previously finished NZ hardwood or pine floor:
| Pass | Grit | Purpose |
|---|---|---|
| 1st | 40–60 | Strip old finish, level boards |
| 2nd | 80 | Remove coarse scratches |
| 3rd | 100–120 | Refine surface, remove 80-grit marks |
| Final | 120–150 | Smooth finish-ready surface |
Always match the edger grit to whatever grit the main drum sander is running at the same time. If your drum sander is on 80-grit, your edger should also be on 80-grit — then both move through the sequence together.
Technique to Minimise Circular Marks
Keep the Edger Moving
Never let the edger sit still while the disc is spinning. The moment you stop moving, the disc digs a deeper circular groove. Use a smooth, sweeping arc motion — move the machine in a wide half-circle following the skirting board, then work back toward the main sanded area.
Work at an Angle to the Grain
On your coarser passes, move the edger at roughly 45 degrees to the grain of the timber. This helps the scratches cut more evenly and makes them easier to remove with the next grit. On your final fine-grit pass, try to move with the grain as much as the tight space allows.
Overlap with the Drum Sander
The transition zone — the strip between the edger's reach and the drum sander's path — is where circular marks most often show up in the finished floor. After each edger pass, use a hand scraper or a random orbital sander (also available for hire) to blend this zone. Work with the grain and use the same grit as your last edger pass.
Don't Press Down
Let the machine's weight do the work. Pressing down increases the cut depth and makes circular marks worse. Hold the edger lightly and guide it rather than forcing it.
Sand Dry and Clean
Dust build-up under the disc causes uneven cutting. Empty the dust bag frequently and make sure the disc is properly seated and not worn out. Hire depots will supply spare discs — ask for a full set when you pick up the machine.
Blending the Edges: The Critical Final Step
After your final edger pass, the area near the skirting boards still needs attention. Use a random orbital sander with 120-grit paper to work over the edger zone, moving with the grain. Follow this with hand-sanding using a sanding block in the very corners the orbital can't reach. This step is what separates a professional-looking result from one riddled with swirl marks.
Choosing and Hiring the Right Equipment
Most hire centres in NZ — including those listed at Mitre 10 and Bunnings — offer floor edgers alongside drum sanders and random orbital sanders. When hiring:
- Ask staff to demonstrate the edger if you haven't used one before
- Hire a random orbital sander at the same time for blending
- Get more sanding discs than you think you'll need — running out mid-job is costly
- Check that the dust bag seals properly; fine timber dust is a health hazard and WorkSafe NZ recommends respiratory protection when sanding
Finishing After Sanding
Once you're happy the circular marks are gone — check by shining a raking light (a torch held low and parallel to the floor) across the surface — vacuum thoroughly and tack-cloth the floor before applying your chosen finish. Products from Resene, Wattyl, and Dulux all offer timber floor finishes suitable for NZ conditions; follow the manufacturer's instructions for recoat times and ventilation.
For information on healthy indoor environments — relevant if you're refinishing floors in a rental — see Tenancy Services.
When to Call a Professional
If your floor has significant cupping, deep gouges, or boards that are loose or damaged, it's worth getting a qualified floor sander to assess the job first. Sanding a badly cupped or structurally compromised floor can make things worse. If you've already sanded and the circular marks are deep and widespread, a professional can re-sand and blend the floor correctly. You can find experienced local floor sanding tradespeople on tradedirectory.co.nz.
