Flap Discs Types + Q&A
What is a Flap Disc?
A flap disc is an abrasive attachment made up of multiple layers of “flaps” of overlapping abrasive, sandpaper-like, sections adhered to a central hub in a wheel design.
As the disc is used to grind metal or other surfaces, the abrasive material will grind down. Once the material on the outer layer is used up, that sheet will automatically tear off to expose a fresh layer of abrasives.
Flap Disc Uses
Flap discs can be used for most of the same purposes as a regular sanding disc. They are excellent for grinding and deburring metal surfaces, removing paint and rust, stock removal, and smoothing out imperfections.
Specialty flap discs can be used for polishing and/or surface conditioning metals as well.
What are 4.5” Angle Grinder Flap Discs Made Of?
The actual sheets are made up of a polyester cloth bonded with abrasive grains, similar to the makeup of sand paper. The grains are available in different grits as well as different materials such as zirconia, aluminum oxide, and ceramic grains.
The backing plate is crafted with a strong fiberglass plate. Fiberglass makes for a lightweight, but rigid backing that is capable of absorbing a notable amount of vibrations creating from grinding any surface.
Specialty Flap Discs
Traditionally, flap discs have overlapping sheets of sandpapers, but in recent years the innovative design has been used to create new products by incorporating materials such as Australian wool for polishing, and nylon webbing for surface conditioning. Each of these varieties has the same fiberglass backing and metal hub, except for the mini quick change discs that use a plastic Type R Roloc-like attachment for die grinders.
Type 27 vs Type 29 Flap Discs (T27 & T29)
The “type” of design for flap discs specifies the angle that the abrasive sheets are aligned into the wheel.
T27 - Flat Discs
Type 27 flap discs are flat across the entire disc. This generally makes the preferred choice for smoothing/blending surfaces as well as flat sanding. Using an angle grinder, T27 flap discs should be used from a 0-15° angle from the surface.
T29 - Conical Discs
Type 29 flap discs have their abrasive sheets have a slight angle on the face of the disc. This design allows for more aggressive grinding and is usually preferred for contouring and shaping surfaces. Using an angle grinder, T29 flap discs should be used from a 15-25° angle from the surface.
Aluminum Flap Discs for Soft Metal
Anyone who has ever tried to grind aluminum or other soft metals with the wrong abrasive grain knows how delicate this metal can be. If you want to use a flap disc to grind aluminum, we carry a special flap disc for aluminum that avoids loading and has a calcium stearate coating to keep the temperature lower while grinding.
These aluminum oxide flap discs can be used for sanding and grinding all soft non-ferrous metals from aluminum and copper to zinc and nickel.
Flap Disc Abrasive Materials
Just like most other abrasive products, there is a variety of different abrasive grain types that can be used for flap discs and each has their own purpose.
Zirconia is the most common grain used for flap discs. It is a tough abrasive with a high cut rate that can grind strong metals like stainless steel and titanium. The grains are self-sharpening which significantly reduces downtime while working.
Ceramic flap discs are another strong abrasive that can grind metal surfaces from carbon steel to aerospace alloys. Like zirconia, ceramic is a friable abrasive grain that continuously exposes new sharp grains, so you can keep working without a dulling disc. A key feature that sets ceramic flap discs apart from others is the low temperature buildup compared to other materials.
Aluminum Oxide is the best flap disc for aluminum and other soft metals. When combined with a white calcium stearate coating, these discs prevent clogging (chip adhesion) which could damage the soft metal being worked on.
High Density Flap Discs
By design, flap discs are made to work consistently for a long time by constantly exposing fresh flaps of sandpaper. High density flap discs are made for individuals who do a lot of grinding and want an abrasive that will last even longer. These XL discs are much thicker and have about 50% more flaps per disc.