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How to get optimum performance from your abrasive flap discs

How to get optimum performance from your abrasive flap discs

Posted on Monday, 1 May 2017 by Clayton Thomas
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Are your abrasive flap discs tearing or not giving you the right finish? There might be some things your flap discs are trying to tell you. Here are some tips on increasing the life of your metal flap discs and getting the best performance...

There's a few options out there and choosing the right one will ensure you get the most out of your flap disc. If you're finding your discs are wearing out too fast, or not giving you the right finish, you could be selecting the wrong disc for your application. Here's a quick guide:

Choosing the right flap disc

Flap disc shapes

The best choice for weld removal, blending and smooth finishing. Use primarily on flat surfaces.


The best choice for aggressive stock removal. Used on both contoured and edge work.


Application and grit


Type Description Use
Zirconia flap discs 
Zirconium gradually wears, allowing the abrasives to provide a more constant level of finish than standard fibre discs 
  • Contoured and edge work
  • Use on:
    • Stainless steel to steel
    • Aluminium 
Combination flap discs   Made up of a combination of abrasive cloth for removal, and softer, surface-conditioning material or blending and fine finishing.

Reduce your time on finishing, with removal and finishing or blending in one operation. 

Produces a consistent and uniform finish.
  • Inexperienced users find it easy to use because it removes material with more control.
  • Soft and flexible and capable of following curves in difficult areas without digging in or damaging the metal like standard hard abrasives.
  • Use on:
    • Stainless steel
    • Aluminium
    • Steel 

Right application - wrong angle

Flap discs are designed to be worked on an angle. The angle depends on your fabrication and what you are grinding, however a general guide would be between 5-10 degrees from flat/level. If the angle is too flat then too many of the disc's grains will be connecting with the metal at once, causing the flap disc to wear a lot faster. If the angle is too high you won't be using enough of the disc. This will result in excessive wearing on only part of the disc, and insufficient sanding of the job.




Adjust your angles. The way to tell if your angles are off is to look at the wear pattern on your sanding discs. Generally the wear pattern on your disc face should be approximately double the disc thickness. So if your flap disc is 6mm thick, then a 12mm wide wear pattern should be visible on the face. If the wear pattern is wider then it indicates your approach is too flat. If the wear pattern is thinner your approach is too high.

I can't handle the pressure!

Pushing too hard on your fabrication will overwork and overheat your flap disc. This will cause the disc to wear out much faster, and reduce the effectiveness of the abrasive. At the same time, if not enough pressure is used the disc will not be engaging with the metal enough to efficiently sand back the surface. This will result in longer sanding times and further wearing.


Listen to your grinder - When the grinder is working properly it should provide a consistent pitch. If you hear the grinder dip and start making a lower noise this indicates the machine is being overworked and you are applying too much pressure. If the pitch goes higher, the abrasive disc may be bouncing along the metal ridges and you will need to apply more pressure.

Consistency is key - Try to apply the same pressure moving forward and backwards. You may naturally apply more pressure moving forward than backward. This can make things even worse as you will overwork and overheat the disc moving forward (you will notice the edging turning orange as the grains glaze over), and the disc will bounce off the metal on the way back. This will be a very inefficient process as not much metal will be removed with each motion.

Slow down, we're going too fast!

Using the wrong speed (RPM) for your flap disc can result in premature wearing, tearing and eventual death of the disc. Choosing the right speed can increase the life of your flap disc by up to 100%. In other words, if you are using the wrong speed, you could be halving the working life of your flap disc!


Choose the right size abrasive flap disc for the tool you are using, and follow the manufacturers recommendations. The maximum safe RPM marked on the flap disc should be greater than or equal to the maximum operating RPM on your grinder. You'll also want to pay attention to tool speed. A grinder with lower power won't be able to perform at the required speed, so won't allow the flap disc to live up to its full potential.

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