Flap Disc Selection Guide

When most people think of abrasives, the traditional grinding disc is usually the first thing that comes to mind, however, in our field of metal surface preparation, flap discs offer many advantages in certain applications like removing rust, edge grinding, deburring and blending weld seams.

What are they?

A flap disc consists of abrasive coated flaps bonded to a backing plate in an overlapping radial formation. This “flapped” formation increases the surface area and reduces the likelihood of stress points occurring.

While flap discs and grinding discs are similar, in that they are both used on angle grinders to shape metal, there are crucial differences which determine when they should be used for your project.

If you are simply looking to achieve a high rate of stock removal, grinding discs are the most common choice. By their nature, grinding discs produce uneven results and leave a coarse appearance, being the compromise of helping get the job done quickly.

Flap discs, however, are easier to control and allow the operator to apply more varied working pressure to perform both grinding and finishing in one efficient process to leave a smoother, even finish ready to apply a new coating. 

Advantages of flap discs

Flap discs offer benefits such as fast stock removal and the ability to grind, blend, and finish with a single product, which can improve project timelines. Other advantages in surface preparation include:

• Less downtime: No disc changes between tasks.
• Cooler operation: Less likely to leave scorch or heat marks requiring re-work.
• More control: Reduced risk of gouging or removing too much material from overly aggressive grinding.
• Smoother finish: Improved surface finish and ready for coating if required.
• Improved safety: No pieces to shatter or fly off during work process.
• More comfortable for operator: Quieter, less vibration and less pressure needed to produce results reduces operator fatigue, especially on long projects. 

Should I choose a grinding disc or flap disc? 

It doesn’t necessarily need to be an "either-or" question as both have some crossover and both and have their own benefits.

In metal surface preparation, they are often used in combination - a grinding disc being used for quick stock removal then followed up by a flap disc to achieve a smoother, blended finish required for stainless steel or surfaces ready for coating.

If you do not need to worry about the finish, then just opt for a grinding disc which will, typically, produce the quicker result.

If you want to do a full grinding and finishing job all in one, you could do so with just a flap disc. It might take longer, but the flap discs are designed for the operator to use them comfortably for a longer period of time. 

Which abrasive should I choose?

Always remember, a quality abrasive offers longer life, avoiding the need to frequently change discs and potentially reducing overall project costs.

For metal surface preparation, the choices for flap disc abrasive grains are: 

CERAMIC ALUMINA

If you are looking for maximum performance in a flap disc, Ceramic is the clear choice. 

Offering fast, aggressive stock removal, the ceramic grains micro-fracture as they grind, constantly exposing new sharp edges and maintaining a high cut rate for the life of the disc.

Ideal for workpieces made from stainless steel, standard steel, tool steel, titanium, high-nickel and high tensile alloys, its fast cut rate and cooler grinding temperature help protect valuable, heat-sensitive components reducing potential discolouration. 

ZIRCONIA ALUMINA

Zirconia Alumina is a sharper abrasive than Aluminium Oxide. It cuts cooler and quicker with less effort required.

The Zirconia Alumina grain is also self-sharpening and withstands high temperature and working pressure allowing for aggressive stock removal and high-performance edge grinding.

With proper use and maintenance, it provides a rapid cut and long lifespan. It is ideal for workpieces made from cast iron, carbon steel, structural steel and stainless steel.

ALUMINUM OXIDE

Aluminium Oxide is a hard, durable grain that delivers a strong rate of material removal, however, aluminium oxide crystals are not self-sharpening and will dull during use.

It removes stock well, and produces a smooth and chatter-free finish making it ideal for general purpose use and working on steels and other non-ferrous metals.

Overall, it provides an excellent blend of performance and value. 

Grit size 

For metal surface preparation in industrial environments, we focus on grit sizes of 40 to 120. Lower grit numbers are best for standard grinding requiring a high material removal rate, while higher grit numbers provide smoother finishes.

Different grit flap discs are often used on the same project with a coarser grit being used for the initial shaping and stock removal followed by a finer grit for blending and finishing.

Below is a general summary of metal processing tasks and grit recommendations:

Heavy stock removal - 40 grit
Weld grinding and blending - 40 to 60 grit
Chamfering and edge bevelling - 60 grit
Deburring and deflashing - 60 grit
Rust removal and blending - 60 to 80 grit
Cleaning and finishing - 80 to 120 grit

METABO QUALITY

TSPC recommends the Metabo range of flap discs for metal surface preparation in demanding industrial environments.

Offering outstanding levels of performance and tool life, all discs meet the highest safety standards and are rated for use with powerful angle grinders.

All discs are contaminant free and glass fibre backed, the most popular style of backing for flap discs, being very strong and durable and helping absorb vibration.

View our range here