Flap Wheels - Schaffner Flapwheels
A flap wheel is an abrasive wheel made from abrasive strips (flaps) radiating from a center hub. Flap wheels come in many different shapes and sizes. The outside diameter of the wheel can range form 4" to 24" and sometimes larger. The hub helps hold the flaps together at the periphery and defines the arbor of the wheel at its center. There are various methods used in holding these flaps to the hub, probably the most common is a glue/adhesive that bonds the flaps together as well as to the hub. There are two basic components to a flap wheel: the hub of the wheel, and the abrasive used in the wheel.
A. Flap Wheel Hub (or Center)
There are basically three types of hubs used in manufacturing flap wheel:
1. Metal Centered Hub-- This type of hub construction can be used with many different type of flaps: coated abrasive, cloth, non-woven abrasive or felt. This hub has become an industrial standard because it lends itself to a wide variety of applications.
2. Cardboard Core Hub -- This is sometimes used in manufacturing flap wheel using non-woven abrasives, but rarely used for abrasive cloth due to the lower dynamic integrity with "heavier" flaps.
3. Heavy Duty Mechanical Hub-- This type of construction mechanically attaches a group of flaps to the hub. It has the advantages of potentially high structural integrity and superior balance re-using the hubs by exchanging used abrasive loadings with new ones.
B. Types of Abrasives for Flap Wheels
There are many types of material that can be used for flaps and placed in flap wheels -- felt, neoprene, buff cloth, cardboard. All of these have some very specific uses in flap wheel. But the most common material used in flap wheels is abrasive flaps -- both woven and non-woven.
Flap wheel abrasives are crystals grouped into two general categories: natural and artificial. Natural forms of abrasive are Diamond, Corundum, Garnet, Quartz and other softer materials found in the earth. Artificial abrasives are manufactured, such as Synthetic Diamond, Silicon Carbide, Aluminum Oxide, Boron Carbide and various aluminas. Silicon Carbide and Aluminum Oxide are the two primary abrasives used in flap wheels. (United States Products Co. Inc. 1995 -- Internet)
1. Silicon Carbide (SiC -- also known as Cystolon) -- A fused, hard synthetic crystalline abrasive often grey to black in color. On a MOHS scale of hardness Silicon Carbide is 9.5. This crystal tends to fracture when under pressure presenting a new sharp edge to the work piece. This causes Silicon Carbide to be fast cutting and well suited to many ferrous metals.
2. Aluminum Oxide (Al2O3 -- also known as Alundum)-- This is also a fused, hard synthetic crystalline abrasive often tan to red in color. The bonds pull the Aluminum and Oxygen elements are very close together causing these two relatively light elements to make a hard, dense crystal. On the MOHS scale of hardness Aluminum Oxide is 9.0. This hard crystal structure has a tendency to slowly dull or round and is hard to fracture.
-- Interesting Note--
A cousin of Alundum (but still an Aluminum Oxide) is Corundum. This is a natural mineral that is mined all over the world. It has a softer crystalline structure than Alundum and therefore is not often used in Abrasive flap wheels (but is frequently used as an abrasive in lapping compounds). Two of the varieties of Corundum are considered gemstones. The red variety is known as a ruby and the other colors are known as sapphires. (Amethyst Galleries, Inc. 1995 Internet)
When to use Flap Wheels
There are several applications that use abrasive flap wheels. Some of the common uses are de-burring (i.e. aluminum or zinc die castings), stress relief (jet engine turbine blades) and as a fine grinding tool to reach non-specific dimension tolerances. Although, these are certainly common uses, probably the most common use is for preparing the work-piece for further finishing steps (i.e. buffing, plating, anodizing, etc.).
There are so many tools available to do de-burring or provide metal stock removal or alter the metals surface finish, why would anyone ever choose to use flap wheels? The answer depends on the purpose that an abrasive was chosen in the first place. There are applications where flap wheels are ideal and there are times when a belt or set-up wheel would be more appropriate. It is helpful to compare both the advantages and disadvantages to using an abrasive flap wheel in comparison to other abrasive tools such as abrasive belts and abrasive set-up wheels:
© 2006 Schaffner Manufacturing | Flap Wheels - Buffing Compounds & Buffing Wheels
