Choosing a Back-Up Pad for Silicon Carbide Discs
By Supergrit Abrasives | Published: 2026-10-18
Category: Buying Guides
Match your back-up pad to the disc size, grit, and sanding task. Learn the key rules for 6-inch PSA silicon carbide discs and avoid common mismatches.
Quick Answer
Choose a back-up pad that matches the disc diameter, uses the same attachment system, and offers a hardness suited to your sanding surface—softer for contours, firmer for flat work.
Why pad hardness matters
The back-up pad's hardness determines how evenly pressure spreads across the disc. A soft pad conforms to curved surfaces and reduces the chance of gouging, but it can round off sharp edges on flat work. A firm pad gives a flatter finish and removes material faster, but it transmits every imperfection in the surface.
For fine finishing with 240 grit silicon carbide discs, a medium or soft pad is usually the safer choice. It lets the abrasive follow subtle contours without cutting too aggressively.
PSA vs hook-and-loop: know the difference
PSA (pressure-sensitive adhesive) discs stick directly to the pad. They are simple to apply, but they do not allow quick disc changes. Hook-and-loop pads let you swap discs instantly, which is handy when you switch grits often.
If you are using PSA discs, the pad must have a smooth, clean surface. Any residue or damage will affect adhesion and cause the disc to slip or wrinkle.
Pad size and disc overhang
The back-up pad should match the disc diameter exactly. A 6-inch disc on a 5-inch pad leaves an unsupported edge that can tear or chatter. A larger pad with a smaller disc leaves the abrasive unsupported at the center, which reduces control.
Always check the pad's diameter before buying. Most standard orbital sanders accept a 6-inch pad, but confirm your tool's specifications.
Decision Rules for Choosing a Back-Up Pad
- Match the diameter: Use a back-up pad that exactly matches the disc diameter. For 6-inch PSA discs, choose a 6-inch pad. Overhang causes edge wear and chatter.
- Match the attachment system: For PSA discs, use a smooth, flat pad without holes or hook-and-loop texture. For hook-and-loop discs, use a pad with the matching loop surface. Check the pad surface before buying—PSA and hook-and-loop are not interchangeable.
- Choose hardness by surface: Soft pads (or soft interface pads) for curved or delicate surfaces; medium pads for general work; firm pads for flat, aggressive sanding. When in doubt, start with a medium pad and adjust based on the finish you get.
- Consider the grit: Fine grits like 240 are for finishing. Use a softer pad to avoid over-cutting and to keep the finish consistent. Pair fine grit with a soft or medium pad for best results.
Product Facts
- 6" SOLID PSA UNBRANDED MIRKA WHITE CARAT DISCS (ROLL) 240 GRIT: These 6-inch PSA discs are supplied in a roll of 100 and come in 240 grit, with a pressure-sensitive adhesive backing for easy attachment. They pair well with a 6-inch PSA back-up pad that has a clean, smooth surface—ideal for fine finishing tasks where consistent adhesion and a fine grit are needed.
6" SOLID PSA UNBRANDED MIRKA WHITE CARAT DISCS (ROLL) 240 GRIT
Who Should Use Which Pad
Best for
- Auto body repair and paint prep using 6-inch PSA discs for fine finishing
- Woodworkers who need a flat, consistent finish on panels or tabletops
Not for
- Detail sanding in tight corners or small profiles—use a smaller pad or a detail sander instead
- Heavy stock removal—use a coarser disc and a firmer pad, or a different tool like a grinder
