FLAP DISC – The Right Cutting And Grinding Disc

What Is The Flap Disc?

Many manufacturing applications benefit from the use of flap discs. What makes flap discs unique among surface preparation tools such as cutting disc and grinding disc?

Flap discs, also commonly referred to as stop wheels, are designed for right-angle grinder applications. They provide aggressive stock removal or precise blending and finishing depending on the needs of the operator. They offer excellent versatility, maneuverability, and lower vibration and noise levels than grinding wheels.

Flap discs are an excellent choice for many applications because they allow the operator to perform grinding and finishing in one efficient, time-saving, and cost-reducing step. They grind like hard abrasive wheels, but with more control, so you reduce the risk of scratching your workpiece, and they remain usable even after areas of the abrasive have worn away because new abrasive is exposed. They also tend to have a softer feel than grinding wheels and reduce the risk of removing too much material from the workpiece by over-grinding.

Basic Knowledge Of Flap Discs

Flap discs have 4 basic components: backing shape, backing type, gain type, and density.

Backing Shape

Type 29 – Conical

  • Built-in angles to increasethe contact area
  • Best for contoured surfaces and edge work
  • Minimize workpiece gouging
  • More aggressive cutting due to higher angle
  • 15°-25° working angle

Type 27 – Flat Shape

  • Best for miters, corners and edges
  • The best choice for finishing complex ornate surfaces
  • Ideal for smooth finishing
  • 0°-15° working angle

Backing Type

Fiberglass Backing

  • The backing will be worn evenly with emery cloth
  • Will not chip or smear ona workpiece
  • Lighter, quieter operation

Plastic Backing

  • Non-scratch, high-strength backing
  • Resistant to extreme temperatures, common chemicals and solvents
  • Some plastic backings are trimmable

Flap Backing: Polyester, Polycotton or Cotton

  • Polyester fiber
  • Capable of withstanding extremely high pressures without degrading the flaps
  • For extreme cutting and edge grinding
  • Cotton
  • For use where maximum fit and soft feel are sought
  • Must be used under light pressure to maximize performance and longevity
  • Polyester-cotton blend
  • Best of both worlds
  • Can withstand high pressure while still maintaining good cutting and finishing
  • Usually used as a starting point for first-time users on slapping disc maneuvers


Grain Type


  • This allows for consistency across a wide range of grinding applications
  • When sanding on steel, stainless steel or aluminum, you should consider choosing a ceramic disc
  • Ceramic also tends to grind cooler, minimizing discoloration while maximizing product life


  • These discs are used for general steel grinding, cutting and finishing
  • An economical choice whenthe cost is the driver




High density flap discs provide the user with approximately 40% more abrasive material. The increase in abrasive material leads to an increase in beating productivity and longer life.