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.

Pros:

• Better for smoothing and blending

• Superior for flat sanding

Cons:

• Not good for contour work or shaping

• Not as effective for stock removal

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.

Pros:

• Superior for contouring and shaping

• Better angle for heavy stock removal

• Grinding and blending with one disc

• More aggressive when grinding

Cons:

• Inferior when used on flat surfaces

• Less effective at smoothing and blending