Clarke Super 7R Edger: Specs, Disc Sizes & Buying Guide

The Clarke Super 7R is the most common floor edger rental for the DIY refinisher. It's lightweight, maneuverable, and essential for sanding the edges and corners a drum sander can't reach. Getting the right discs—and understanding PSA vs. hook-and-loop—makes the difference between an amateur-looking floor and professional results.

Clarke Super 7R Specifications

Specification	Value
Disc Diameter	7 inches
Center Hole	7/8 inch OR 5/16 inch (check your machine)
Motor	1.5 HP
RPM	175–2500 (variable speed)
Width	~5 inches (working width along wall)
Weight	~35 lbs
Best For	Edging 300–800 sq ft floors; pair with drum sander

Disc Size: 7 Inches Diameter

The Clarke Super 7R uses a 7-inch disc—this is standard and specific to the machine. Do not substitute 5-inch, 6-inch, or 8-inch discs; they won't fit correctly.

Two Center Hole Sizes (Critical)

This is where most DIYers get stuck. The Super 7R comes with one of two center hole sizes:

7/8 Inch Center Hole

• Most common on newer Clarke 7R models
• Standard on most generic 7-inch edger discs
• If you're unsure, measure your machine's arbor (spindle)

5/16 Inch Center Hole

• Found on some older Clarke models
• Less common; harder to find discs for this size
• Special-order or proprietary discs only

How to identify your machine: Look at the center spindle on your Clarke 7R. Measure the diameter. It's either 7/8 inch (looks like a thick bolt) or 5/16 inch (looks like a thin rod). If unsure, ask the rental company or check the manual. Ordering the wrong size is a waste of money and time.

PSA vs. Hook-and-Loop Discs

PSA (Pressure-Sensitive Adhesive) Discs

• How they work: Sticky backing adheres directly to the machine's rubber pad. No fasteners needed.
• Application: Peel backing and press the disc onto the pad. Align carefully on the first try; repositioning breaks adhesive.
• Removal: Peel off after sanding (reuse if not damaged). Takes some effort; pulling too hard can tear the disc.
• Cost: Slightly cheaper per disc (~$2–$4)
• Best for: Quick jobs where you won't change discs frequently. Once-through screening or light edging.
• Downside: Adhesive weakens over time. A disc might slip partway through use. Heat from extended sanding can reduce adhesion.

Hook-and-Loop Discs (Recommended)

• How they work: Velcro-like backing grabs a hook-and-loop pad (like Velcro) attached to the machine.
• Application: Press firmly and evenly; it grabs instantly and holds securely.
• Removal: Peel off smoothly; less effort than PSA. Discs can be reused many times if not damaged.
• Cost: Slightly more expensive per disc (~$3–$5). But the machine needs a hook-and-loop pad installed first (~$10–$20, one-time cost for a rented machine).
• Best for: Professional work, multiple-grit jobs, or longer refinishing projects. The convenience is worth the small extra cost.
• Advantage: Holds perfectly even under vibration. You can change discs 20 times without slipping. Discs last longer because they aren't mangled during removal.

Which Should You Choose?

For a typical DIY floor refinish:

• Hook-and-loop is better. Yes, the machine costs a bit more to set up, but the convenience and reliability are worth it. You'll change discs multiple times (different grits), and hook-and-loop makes this painless.
• PSA works if you're only doing one grit pass (e.g., just light screening on a drum-sanded floor). But most edging requires 2–3 grits, making multiple PSA changes annoying and error-prone.

Pro tip: Ask your rental company if the machine comes with hook-and-loop pad installed. Many do now. If not, ask them to install one for a small fee; it'll save you frustration.

Disc Recommendations by Grit

Virginia Abrasives 7-Inch Discs (Recommended)

Virginia Abrasives makes excellent 7-inch edger discs. Available in PSA or hook-and-loop backing:

Grit	Purpose	Used After	Closed or Open Coat
36 or 60	First pass; removes old finish	Before drum sander or with it	Closed coat
80	Second pass; removes 60-grit scratches	After 60-grit drum/edger	Closed coat
120	Final pass; prepares for stain	After 80-grit drum/edger	Closed coat
150	Ultra-fine screening between coats	Between polyurethane coats	Closed coat

Alternative Brands

• 3M or Bosch: Premium discs, slightly higher cost (~$4–$6). Excellent consistency; worth it for fine furniture or high-end floor work.
• Norton: Solid quality, mid-range price (~$3–$5).
• Generic discs: Avoid. Variable quality; some are dull out of the box.

How Many Discs Do You Need?

Room Size	60 Grit	80 Grit	120 Grit
250 sq ft	2–3	2–3	1–2
400 sq ft	3–4	3–4	2–3
600 sq ft	5–6	5–6	3–4

Note: Edger discs wear faster than drum sander sheets because the 7R operates at very high pressure and RPM. Budget generously. You can reuse hook-and-loop discs that aren't completely dead for final light passes.

How to Change and Install Discs

PSA Disc (Adhesive-Backed)

1. Turn off the machine and unplug it.
2. Clean the rubber pad with a lint-free cloth. Remove all dust and old adhesive residue.
3. Peel the backing from the new PSA disc halfway.
4. Align the disc carefully on the pad. Start at one edge and press firmly.
5. Peel the rest of the backing and press the entire disc firmly onto the pad, working from center outward to remove air bubbles.
6. Wait 1–2 minutes before operating; adhesive needs time to set.

Hook-and-Loop Disc

1. Turn off the machine and unplug it.
2. Check that the hook-and-loop pad is installed on the machine. (If not, have the rental company install one.)
3. Press the new disc firmly onto the pad. Align the center hole and press outward in all directions.
4. It grabs instantly; you're ready to go. No waiting for adhesive.

Removing a Worn Disc

PSA: Peel carefully from one edge. If it tears, use a scraper to remove residue.

Hook-and-Loop: Peel smoothly from one edge. Very easy removal.

Clarke 7R Edging Technique

Basic Technique

• Hold the machine steady with both hands. Don't let it tip or lean; the disc should kiss the floor edge gently.
• Keep the disc tilted slightly toward the wall. You want the edge of the disc (not the flat face) to kiss the wall/baseboard. This gives you a clean line.
• Move steadily along the wall. Don't linger; keep a constant slow walking pace.
• Use steady pressure. Don't jam the machine into the wall. Light, consistent pressure lets the disc do the work.
• Overlap your passes slightly along walls and in corners to avoid missing spots.

Corners and Tight Spots

• Inside corners: Tilt the disc to 45 degrees and ease it into the corner. Make short passes.
• Around door frames: Carefully edge around the frame. The disc edge should stop short of the frame trim.
• Under radiators and obstacles: Reach under with the disc as far as safely possible. Hand-sand any spots the machine can't reach.

Avoiding Common Edge-Sanding Disasters

• Don't press hard: Excessive pressure gouges the floor and breaks discs. Light pressure = better results.
• Don't leave the disc spinning in one spot. It will burn or gouge the wood instantly.
• Don't tilt the disc flat against the floor. The flat disc surface is too aggressive for finishing; you want the edge doing the work.
• Don't skip variable speed. Lower RPM (500–1000) for heavy cutting, higher RPM (2000–2500) for final passes. Most rental 7Rs have variable speed; use it.

Variable Speed and When to Use It

Low Speed (175–1000 RPM)

• First pass (36 or 60 grit): More aggressive cut
• Prevents disc from glazing (surface getting shiny from heat)
• Better control; easier to handle

High Speed (1500–2500 RPM)

• Fine grits (120+): Smoother finish
• Light passes: Quick work on nearly-sanded edges
• More vibration; harder to control

Pro setting: 60 grit at 800–1200 RPM, 80 grit at 1200–1500 RPM, 120 grit at 1800–2500 RPM.

Troubleshooting Problems

Disc Slips or Spins Without Cutting

• PSA: Adhesive is weak. Peel off and re-install, ensuring no air bubbles. If it still slips, the pad is dirty; clean it.
• Hook-and-loop: Pad is worn or missing. Ask rental company to replace or install a new one.
• Disc is glazed: Surface is shiny, not cutting. Lower RPM or change to a fresh disc.

Disc Tears or Chunks Come Out

• Too much pressure. Lighten your touch.
• Disc hit an obstacle (nail, wood splinter). Inspect floor for hazards.
• Disc was defective out of the box. Replace it.

Uneven Sanding (Dips or Miss Spots)

• Not overlapping passes enough. Make longer, more overlapped passes.
• Tilting the disc inconsistently. Keep angle steady.
• Moving too fast. Slow down; the disc needs time to cut.

Complementary Techniques: Hand Sanding Edges

Even with an edger, some spots are unreachable: very tight corners, under baseboards, around door hinges. Hand-sand these areas with 80–120 grit to blend.

• Use a sanding block for more control
• Sand with the grain
• Light pressure to match edger results
• This final detail work is what separates pro-looking floors from amateur jobs

Need the full grit progression? See our sandpaper grit chart for the complete NWFA-aligned sequence with machine compatibility and sheet counts.