Flap Wheel

A Flap Wheel is a type of rotating tool that is used on a grinder. It is a wheel made from strips (or flaps) of abrasive material radiating from a central hub and is used for sanding. The basic components of Flap Wheels are (1) the hub of the wheel and (2) the abrasive used in the wheel.

 

The outside diameter of a flap wheel can range from 4″ to more than 24″. The hub defines the arbor of the wheel at its center. Various methods are used to fasten the flaps to the hub. The most common is glue or adhesive that bonds the flaps together and to the hub. Three types of hubs that can be used for a flap wheel are the metal-centered hub, the cardboard core hub, and the heavy-duty mechanical hub.

 

Abrasive flaps (both woven and nonwoven) are a much more common material for flap wheels than materials like buff cloth, cardboard, felt, or neoprene, although these other materials have their specific uses too. Flap wheel abrasives are crystals that may be natural or artificial. Natural crystals include diamond and quartz, while the major ones that are artificial or manufactured are silicon carbide (SiC or carborundum) and aluminum oxide.

 

Silicon carbide is a fused crystalline abrasive that is 9.5 on the Mohs scale of hardness. It has a tendency to fracture under pressure, thus presenting new sharp edges to a work piece and making SiC fast-cutting and well suited to ferrous metals. Aluminum oxide is also a fused, hard crystalline abrasive (9.0 on the Mohs scale), but unlike SiC, it is hard to fracture and tends to slowly dull.

 

Selecting the correct flap wheels depends on the machine you use, the rpm rating of the drive spindle, and the arbor size. Because flap wheels do not have the backup support that abrasive belts do, the normal rules for selecting grain type and grit do not apply. Aluminum oxide grain type is used on soft or hard materials, while silicon carbide produces a mirror finish on stainless and aluminum.

 

With a flap wheel, you can produce a finish that is about two grades finer than with an abrasive belt. For improved roughing, 80 grit and rougher is advisable. You should also take a look at a flap wheel parameter table.

 

Mounted flap wheels are available in diameters such as 1″, 1 1/2″, 2″, 2 1/2″, and 3″. They are mounted on a 1/4″ spindle and will fit almost any 1/4″ tool. On the other hand, unmounted flap wheels are available in diameters like 4″ and 6″.