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Black round foam backup pad, 4 inch diameter, hook-and-loop face

3M

3M 924 Hook-and-Loop Disc Backup Pad 4 in 13,000 RPM

SKU CH-6WJB-7CXY6 MPN 924

A 4-inch foam backup pad with hook-and-loop attachment runs at 13,000 RPM for quick disc changes

  • TypeSanders
  • Color/FinishBlack
  • Hook-and-loop mount enables fast disc changes
  • 13,000 RPM rating supports high-speed sanding tasks
  • 4-inch diameter fits standard disc sizes
  • Hard-density foam provides firm backing for consistent finish
  • Dual Lock hook type 170 delivers strong grip on abrasive discs

4-inch Hook-and-Loop Backup Pad

The 3M 924 is a 4-inch round backup pad built for hook-and-loop abrasive discs. Its hard-density foam body and straight 1/4-inch shaft fit directly into compatible sanders. The pad uses a Dual Lock hook type 170 fastening system for quick disc changes. It is suited for technicians and DIY users who need a reliable mounting surface for surface-preparation work.

Thermals noise and power draw

The pad itself has no motor, electronics or moving parts, so it generates no heat, noise or electrical draw. Thermal and acoustic performance depends entirely on the sander it is mounted to. The hard foam construction resists deformation during extended sanding sessions. No vacuum holes are present, so dust extraction must be handled by the tool or external equipment.

13,000 RPM maximum operating speed

The single specification that decides fitment is the 13,000 RPM maximum operating speed. The sander used with this pad must not exceed that speed, or the pad and disc can fail. Buyers whose tools run faster need a higher-rated backup pad. The 1/4-inch straight shaft and 4-inch diameter must also match the tool's spindle and guard requirements.

Highlights

  • Hook-and-loop mount enables fast disc changes
  • 13,000 RPM rating supports high-speed sanding tasks
  • 4-inch diameter fits standard disc sizes
  • Hard-density foam provides firm backing for consistent finish
  • Dual Lock hook type 170 delivers strong grip on abrasive discs

Specifications

TypeSanders
Brand3M
Model924
Color/FinishBlack

Questions about this item

How do I attach the 924 backup pad to a tool with a 1/4 in straight shaft, and what step is often missed?

Slide the pad onto the 1/4 in straight shaft and tighten the tool's spindle lock or collet securely; the step often missed is verifying the tool's maximum RPM does not exceed 13,000 RPM before use.

When will the hook-and-loop surface on this pad need replacement?

Replace the pad when the Dual Lock Hook Type 170 loops no longer grip abrasive discs firmly, which typically occurs after repeated disc changes or when discs slip during operation.

What is the first limit reached when running this 4 in pad continuously at 13,000 RPM?

The maximum operating speed of 13,000 RPM is the primary limit; sustained use at this speed can generate heat in the hard foam body, potentially reducing hook-and-loop holding power over time.

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