Trimmable Flap Discs Provide Versatility for Grinding and Finishing Applications

By Rick Hopkins, senior product manager,  Weiler Abrasives Group

Flap discs are a commonly used abrasive product in metal finishing applications that offer great benefits for productivity and efficiency. With a flap disc, operators can grind and finish with one product so there’s no need to switch from a grinding wheel to a resin fiber or blending disc. This simplifies product inventory, reduces the downtime spent on product changeover and helps operators complete jobs faster — saving time and money.

Flap discs are available in numerous grit sizes and material options. Some flap discs are also available with a trimmable backing plate made of glass-filled nylon, which allows the operator to remove the backing gradually to maintain the optimal flap overhang for blending and finishing.

So why consider a flap disc with trimmable backing for your application? The outside edge of the flap, where it extends past the backing plate, is more flexible.

The operator can apply less pressure to blend the base material and reduce the risk of gouging the metal. This is especially helpful when working on curved parts since the flaps and backing plate will also curve to match the shape during the process.

Choosing a Flap Disc

Selecting the right flap disc for your application depends on many factors. It’s important to consider the workpiece material, size, orientation, and the desired finish and results. 

The way a flap disc performs depends on the disc’s abrasive material, cloth material, and grit size. There are three common grain types and each offers specific benefits in certain applications.

1. Aluminum oxide flap discs cost less upfront and provide a consistent finish; however, they have a shorter product life.
2. Zirconia alumina flap discs are more heat-resistant and more durable than aluminum oxide flap discs, which allow them to maintain their sharpness longer.
3. Ceramic alumina flap discs feature grains that fracture so they keep a sharp edge and offer good heat resistance. They are the most expensive of the three grains but last the longest.

Choose between a Type 29 style and a Type 27 style flap disc. Type 29 discs have flaps that are pressed at an angle, providing maximum aggression and surface for fast stock removal. They provide the best performance at higher grinding angles (15 to 35 degrees).  In comparison, Type 27 discs are flat, making them better suited for flat surfaces and lower grinding angles. They offer smooth grinding, blending and finishing.

Keep in mind that the choice of flap disc impacts productivity, overall costs, quality and the finished appearance of the material.

Properly Trimming a Flap Disc

Every trimmable flap disc is marked to specify how much the backing can be safely trimmed. This varies by product manufacturer. Weiler Abrasives Group recommends a maximum trim of 3/8 inch from the edge of the original backing plate.

Follow these key best practices for trimming:

1. Select a sharp metal piece or sharp metal corner.
2. Bring the flap disc up to speed on a right-angle grinder and using a slow, steady motion, lift the disc until the top of the flaps contact the metal.
3. Push the disc directly into the metal, applying moderate pressure. Apply the pressure inward to avoid damaging the flaps.

Trimmable flap discs can provide great versatility in the right blending and finishing application since they can be trimmed to suit the needs of the operator. They are especially well-suited for applications where it’s difficult to reach the work or when a specific material finish is a priority.

If you have questions about whether trimmable flap discs are right for your application, consult a manufacturer to get more information about the best options.