Quick Answer

Use 3" pads on angle grinders for edges, stairs, counters and small repairs. Use 5" pads on mid-size swing machines and compact walk-behinds. Use 7" pads on large planetary grinders and high-speed burnishers for open warehouse, retail and factory floors. Never buy pads by price — buy them to match the plate on your machine, because a pad that does not fit the holder cannot transfer pressure correctly.

Which Pad Fits Which Machine

Pad size	Typical machine	Coverage per pass	Best for
3" / 75 mm	Angle grinder, hand polisher	~15 cm	Edges, stairs, counters, spot repairs
5" / 125 mm	Swing machine, compact walk-behind	~25 cm	Mid-size floors, showrooms, residential garages
7" / 180 mm	Planetary grinder, burnisher	~35 cm	Warehouses, retail, factories, open floors

Why Size Changes the Finish

Pressure is weight divided by pad area. A heavy machine on a 3" pad concentrates pressure on a small circle, cuts fast, and heats the pad quickly — good for edges, bad for open floors where it leaves swirls. The same machine on a 7" pad spreads that weight over a wider area, cutting slower but producing a flatter, more uniform gloss. This is why contractors keep two machines: a small edge grinder and a large production grinder.

Working the Edges First

Professional polishing starts with edges. Run the 3" pads along the walls, door frames, pipes and stair treads before the big machine enters the room. When the walk-behind reaches the wall, the edge work is already done to the same grit. Skipping edges and trying to reach them later means coming back on hands and knees with a small machine after the floor is finished — more expensive and harder to match.

Product Match by Size

• 3": our 3'' Diamond Resin Floor Polishing Pads (JOY-RFP-05) and the 3'' Ceramic Bond Diamond Transitional Grinding Pads (JOY-RFP-T1) for the metal-to-resin step on edges.
• 5": the 5''/125mm Diamond Resin Polishing Pads for Concrete Terrazzo Floor (JOY-RFP-S1) for standard residential and showroom floors.
• 7": the 7''/180mm Spiral Diamond Resin Polishing Pads (JOY-RFP-S3) for production passes on large commercial floors.

Common Sizing Mistakes

• Running 7" pads on a small grinder: the machine cannot keep the pad flat, so the edge wears fast and the center never contacts the floor.
• Running 3" pads on open floor: too slow, too hot, too many swirl marks.
• Mixing sizes on one plate: uneven pressure pulls the machine and leaves a patch.
• Ignoring the hole pattern: some 5" pads screw on, others velcro — check before you order.

Frequently Asked Questions

Q: Can I use 5" pads on a 17" burnisher?

A: No. A burnisher uses a full 17" driver with velcro; a 5" pad would skate and leave rings. Use burnishing pads made for the plate.

Q: Is a bigger pad always better?

A: Only on a machine heavy enough to drive it. A light domestic polisher on a 7" pad barely contacts the floor and polishes slowly.

Q: How many pads do I need per set?

A: Walk-behinds use three or four pads per plate; angle grinders use one. Buy them in sets matched to your plate count.

Conclusion

Pad size is a machine decision, not a price decision. 3" for edges, 5" for mid-size floors, 7" for production. Keep the edge grinder loaded from the same grit sequence as the big machine, and the whole floor will finish as one piece. Contact JOY TECH for pads sized to your grinder and burnisher.