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Abrasives Basics
04 February, 2021

Choosing the Best Abrasive Flap Disc for Sanding and Grinding

25 Years ago nobody knew what an abrasive flap disc was.  Today they are the most common grinding disc for metal fabricators.

Abrasive flap discs offer everything from aggressive and consistent stock removal through to fine finishing, pre-polishing and even mirror polishing solutions. So given the benefits of flap discs, what is the best abrasive flap disc for my metal fabrication work?

You need to consider the shape of the disc, the abrasive grit size, the grit type and also what difference if any the backing or a flexible edge will make.

n.b.  We will be considering only 40 to 120 grit flap discs in this blog for finishing applications please consult other blog options.

What Abrasive Flap Discs Do You Need?   – Flap Disc Shapes

Abrasive flap discs are designed for use on angle grinders, allowing them to work at a shallow angle or even flat to the metal surface.  The angle at which the disc is presented to the workpiece will change how aggressive the grinding action is.  A shallow angle allows for more control and consistent grinding.  A steeper angle increases the grinding pressure and therefore speed of cut on a single point but makes it easier to dig in to the metal.  Flap discs provide the same action as a traditional sanding disc but with significant increase in disc life.

To assist with this three types of flap disc are now commonly made:

  • Conical shaped discs
  • Flat faced discs and
  • Flat faced discs with a flexible edge

Flap Discs – Flat ConstructionWhat Abrasive Flap Discs do you need? - Flat faced ceramic flap discs

Flat faced discs are generally preferred for finishing or more controlled grinding applications where a lower grinding pressure is applied to the disc.  Note:  which shape of flap disc you choose to use is entirely personal preference.  Both flat & bevel edged flap discs will grind and sand equally well.



Conical Disc – Bevel Edge ConstructionWhat abrasive flap disc do you need? - bevel edged ceramic flap discs

Conical or bevel edged flap discs are generally preferred for high aggression applications and are by far the most popular shape of flap disc on the market. The bevel on the flap disc has a 15 degree angle, if the operator then works the grinder at a 15 degree angle to the workpiece then the abrasive face can grind flat to the workpiece.  Consequently conical faced flap discs are by far the most common for metal grinding and fabrication applications.


Plastic or Glass Fibre Backing on the Flap Disc?

Originally flap discs were all supplied with an aluminium backing plate but as the discs became more commonly used the glass fibre backing has become the standard.  With a semi rigid backing it allows for high aggression grinding whilst allowing some control.

If greater control and/or reduced vibration is required then it is worth considering the plastic backed flap discs which increase the control and conformability of the flap disc but they will reduce the overall grinding power slightly.

Hints & Tips:  Looking for high aggression flap discs?  Glass fibre backed discs are the best start point.  Need more control?  Consider reducing the grit size, looking at the flexible edge disc options or a plastic backed flap disc


What is the Best Abrasive Flap Disc? –  Abrasive Grit

Apart from choosing the size of the abrasive grain the most important question is which type of abrasive grain will give me the best cut / life / cost ratio.  Zirconia discs are perhaps the most common disc on the market presently. There is however a new kid on the block with the ceramic aluminium oxide flap discs which are the future of power grinding.

Ceramic aluminium oxide:  This technology gives a great cut under high pressure grinding applications.  Early iterations of ceramic flap discs had a great initial cut but then glazed over, or  just stopped cutting.  This is not a problem with the latest generation of Cibo Ceramics.  In 40 and 60 grit forms we recommend ceramic grain grinding on steel, stainless steel and aluminium as well as on high alloy metals such as waspalloy.   For Cibo Ceramics flap discs choose the Performance and Ultimate Line flap disc ranges from Cibo Abrasives. 

Zirconium Oxide:  Good quality zirconia flap discs are a high quality blend of zirconia and aluminium oxide grain which provides an excellent cut vs cost ratio.  They are traditionally supplied for general steel grinding applications.  The Cibo Industrial Line products are all made using a premium zirconia abrasive cloth.

Aluminium Oxide:  Once upon a time we supplied aluminium oxide abrasive flap discs but the technology has moved on and our customers trust us to recommend the best products for their application.  The only advantage of aluminium oxide flap discs is that they are cheap to buy.


What is The Best Abrasive Flap Disc? – Grit Size…

That is the wrong question.  The best grit size depends entirely on how much metal you need to grind and how good a finish you need afterwards.

I need a disc where I just need to grind metal quickly: 40 grit.  Simple, and on steel, stainless steel and aluminium a ceramic 40 grit will grind the fastest of all.

I need good stock removal but I may need to refine the finish afterwards: 60 grit is a great start point.  60 grit flap discs will still grind a lot of metal but the finish is significantly better than a 40 grit.

Lighter weld removal and shaping only: 80 grit will be the right disc for you.  Particularly on sheet metal with stainless steel tig welds.  80 grit is the coarsest disc we would recommend and we often recommend finer.

Hints & tips:  For fast grinding and a better finish switch from zirconia flap discs to the Cibo Ceramic discs and you can often go a grit finer to get the same stock removal with a much better finish.


Buy your premium Cibo Abrasives flap discs here.

See more of our Related Posts below:

abrasive angle grinder, abrasive finishing systems UK             FSC 120 grinding stainless steel, abrasive finishing systems UK

Grinding & Finishing            Grinding Stainless Steel Welds

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