Product Description of the Turbo Zirconia Flap Discs, 10/Pack
Due to the very aggressive and fast-cutting nature of the grain, zirconia is generally only available in the coarse to medium grit range (often no finer than P120.) For finer finishing stock removal is not the priority so less pressure is likely to be applied and zirconia would not therefore be suitable.
Zirconia is in some cases supplied with a “topsize” (also known as “top coat”, or “supersize layer”.) This is a coating which is sprayed on to the grit to act as a coolant when working on heat-sensitive metals such as stainless steel and exotic alloys, and therefore reduce discoloration or burning. It can however also act as a lubricant to help reduce loading (where stock removed from the workpiece builds up on the abrasive and makes it less effective) on softer metals such as aluminium. The presence of a topsize does reduce the aggressiveness of the grain however, and so it is best not to have one if discoloration will not be an issue, for example when working on mild/carbon or structural steel.
With zirconia flap discs in particular, the power of the operator’s angle grinder is an important factor – the higher the content of zirconia and the tougher the backing the more powerful it needs to be in order to break down the grain and perform more effectively. Conversely a lower grade flap disc will wear much more quickly if used on a high powered grinder. As a general rule air powered grinders are usually quite powerful and will therefore often be best served with a tough poly-cotton backing & high grade zirconia, the same for electric tools with power ratings of 1000 watt and above while lower grade discs with less durable backings would be more suitable for lower powered units.