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Fig. 6. Cloth bias buffs in order of increased density from closed face (left to right: 0, 2, 4, 6) to open face (far right) design. sisal buff is usually made with woven sisal interlaced with 86/80 cloth. Acid or rope sisal is sometimes used. The cloth may be mill or dip treated (Fig. 10). The spoke or unit bias buff runs cool- er than standard bias buffs and has a knee-action flexibility that gives supe- rior contour-following ability. The width and number of the individual units is varied within limits. The range of buff density, or hardness, is varied by choice of materials, treatments, (buff center size) plies, and type of radial stitching. Some complex products are best fin- ished with this type of buff. FLAP BUFFS The flap buff (Fig. 11) utilizes separate flap units placed at right angles to the direction of rotation of the wheel. Each flap supports the other to produce a smooth running wheel. Flap wheels were originally designed for bumper polishing and buffing operations. Flaps are made of coated abrasives, sisal, cloth and combinations thereof. POLISHING WHEELS Polishing wheels are usually made of conventional cloth buff sections glued or cemented together. Canvas disks are cemented to the sides to protect the sewing. Glue or cement is applied to the face. Faces are struck with a pipe at angles and cross-angles to form a uniform crisscross of cracks on the polishing surface and provide sufficient resiliency to allow the wheel to make better contact with a workpiece. Buff sections used to make polishing wheels are generally spiral sewn and made of various types of cloth, sisal, canvas, or sheepskin. Solid, one-piece wool felt, and bull neck and walrus hide are occasionally used. Conventional straight buff sections that are glued together may cause streak- ing during polishing. An alternative involves inserting pie-shaped segments or oth- er spacers between the buff sections to result in a "nonridge" polishing wheel that eliminates streaking. Various abrasive and adhesive combinations are used to grind, polish, and satin finish. These include liquid, graded aluminum oxide abra- sives, greaseless compounds and burring bar compositions. BUFFING EQUIPMENT Significant improvements have been made in buff wheels and buffing com- pounds to provide consistent and predictable performance. This has helped manufacturers of automated buffing machines to develop automated equipment for low- as well as high-volume requirements and to minimize labor and overhead in the finishing operation. MACHINE DESIGN Mechanical buffing systems have a motor-driven shaft to which the buff wheel is applied. In addition, most machines will have a positioning mechanism, a fin- ishing lathe, and workpiece-specific fixtures. 40