Choosing the Best Flap Disc for Sanding and Grinding

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    25 Years ago nobody knew what an abrasive flap disc was.  Today they are the most common grinding disc for angle grinders, but sometimes it can get confusing when choosing the best flap discs for your sanding job.

    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 flap disc for sanding and grinding metal fabrication work?

    Consider disc shape, abrasive grit size, the abrasive grit type and also what difference the backing or a flexible edge may make.

    In this article we will be considering 40, 60, 80 and 120 grit flap discs. For finer detail sanding check out our unitised flap discs or the Cibo RCD Combi discs.


    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.  The steeper angle increases the grinding pressure and therefore speed of cut. But a steep angle 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.

    We supply three shapes of flap disc:

    Conical Flap Discs

    Conical or bevel edged flap discs are generally better for high aggression applications. The bevel on the flap disc has a 15 degree angle. If the angle grinder is held at 15 degree angle to the workpiece then the abrasive face will grind flat to the metal. Consequently, conical faced flap discs are by far the most common for metal grinding and sanding.

    Best Flap Disc for Sanding: Conical Flap Discs
    Flat Faced Flap Discs

    Choose Flat faced discs for finishing or more controlled grinding applications with a lower grinding pressure is used. 

    Hints & Tips:  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.

    Best Flap Disc for Sanding: Flat Flap Discs

    Which is Better: Plastic or Glass Fibre Backed Flap Discs?

    Originally flap discs were made with an aluminium backing plate. As flap discs became more commonly used the glass fibre backing became 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 consider plastic backed flap discs which increase the control and conformability of the flap disc. Note: they will reduce the overall grinding power.

    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 Type of Abrasive Grain Type Should I Choose?

    Apart from choosing the size of the abrasive grain the most important question when picking the best flap disc for sanding is which type of abrasive grain will perform best.  

    Zirconia discs are perhaps the most common disc on the market presently.  There is however a new kid on the block. Ceramic aluminium oxide flap discs are the future of power grinding.

    Ceramic Aluminium Oxide

    The Ceramic aluminium oxide technology gives the best cut under high pressure grinding applications.  Early iterations of ceramic flap discs had a great initial cut but then just stopped cutting.  This is not a problem with the latest generation of Cibo Ceramics.  40 grit flap discs and 60 grit ceramic flap discs are the best for grinding on steel, stainless steel and aluminium as well as on high alloy metals such as waspalloy.   For premium performance 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 zirconium 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. For stainless steel grinding our FSC zirconia has a cotton backing. When steel grinding our FNC zirconia flap discs have a stronger poly-cotton backing.

    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 Flap Disc Grit Size?

    The best grit size depends entirely on how much metal you need to grind and how good a finish you need.

    Just need to grind metal quickly: 40 grit flap discs.  Simple. On steel, stainless steel and aluminium a ceramic 40 grit will grind the fastest of all.

    Good stock removal is needed but the finish matters: Start with 60 grit.  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 tig welds 80 grit flap discs are 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. You can often go a grit finer to get the same stock removal and achieve a much better finish.

    To see the complete Cibo flap disc range follow this link: Cibo flap discs for use on angle grinders and air sanders.

    Or here for the metal finishing discs which will fit directly onto an angle grinder including

    • SAG unitised discs
    • MAG unitised
    • Surface conditioning flap discs.
    • VAP felt discs for angle grinders
    Best Flap Disc for Sanding: Unitised Flap Discs

    Our Flap Discs are produced by Cibo Abrasives.

    Hopefully you know now which is the best flap disc for your sanding job. Still don’t know? Drop us an email or give is a call for some technical advice.

    Email: sales@abrasive-systems.co.uk

    Phone: 01677 470795