Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 37 of 707

rake, a cloud of threads may fly off. This shortens buff life, increases com- pound consumption, and adversely affects finish. Also available are solid bias sisal buffs, with every other layer being cloth, and rebuilt buffs made from reclaimed material. CONVENTIONAL SEWN BUFFS Fig. 2. Full disk buff. Conventional, full-disk buffs for heav- ier buffing (cut) are sewn in various ways (Fig. 3). Closer sewing is speci- fied for cutting harder metals and for removing deep imperfections. Concentric sewing causes a buff section to become harder as it wears closer to the sewing and softer after wear causes the sewing to break through. Spiral sewing results in more uniform density. Square sewing pro- duces pockets that help the buff wheel to retain more buffing compound. Radial sewing, sometimes called sunray sewing, and radial arc sewing provide other vari- ations. Tangent, parallel, ripple, zigzag, cantilever, and petal sewing are used for similar reasons. Special sewing, other than spiral, which is done on automatic machines, involves more labor in the buff manufacturing process, thus increas- ing the price per buff. Folded or Pleated Buffs Folded buffs consist of circles of cloth folded twice to form a quarter circle, result- ing in a "regular-pocket" buff (18 ply), or, for more cut, three times, to form eighths of a circle to constitute a denser "superpocket" (34 ply). The segments are laid down to form a circle, with each segment overlapping the previous seg- ment. They are sewn around the arbor hole and partway to the periphery. The folds form pockets that hold compound and flex sufficiently for contour-fol- lowing capacity. Folded buffs share three design deficiencies: lack of center ven- tilation, a tendency to fray, and waste of material in the unused center. Pleated Buff Airway buff cloth may be accordion pleated to present more angles of material to the surface of the product to be finished. Pleating results in more cloth angles to reduce streaking and improve coloring characteristics. Better cutting is also achieved in some applications. Packed Buffs Buffs may be packed with spacers consisting of cloth or paper inserted between the larger diameter plies. The same spacer principle is used between buff sections. Both measures result in a softer wheel face. The packed buff construction is effec- tive in contour buffing applications. A version of the packed buff, for threaded, tapered spindles (2-12-in. diame- ter), is used in the jewelry industry. The center is hardened, usually with shellac. The sides of the buff may be reinforced by leather disks. Pieced Buffs Pieced buffs may be used in place of sewn full-disk buffs. They are made from rem- nants of cloth left over in the manufacture of other textile products. Such buffs 36

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