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Fig. 3. Sewn buffs. require one of the types of sewing used for full disks in order to stay together in use. The chief virtue of pieced buffs is their higher value owing to the lower cost of materials. They usually are sold by the pound (see Table II). BIAS-TYPE BUFF WHEELS Bias buffs are more frequently used than conventional forms. They combine flex- ibility and cutting power. Bias buffs are cool running and resist burning. They are naturally ventilated. Side openings in flanges, center plates, and tabs, resulting in spacing between sections, enhance their cool-running characteristics. By using material cut on the bias, the threads form an "X" at the periphery of the buff. Threads are held at a 45° eling (Fig. 4). angle by cross-threads. This minimizes fraying and rav- Strips of bias-cut fabric are sewn into continuous rolls. After the rolls are cut to proper length, they are wrapped around a hub or core. They are then pulled to the desired inside diameter within the channel, usually by means of steel blades in an "Iris" machine. Straight-wound material wrapped around an oversized wheel results in a convoluted or "puckered" face; thus, the term "puckered" buff. The "puckered" face design of bias buffs tends to break up lines left in the sur- face of a product from previous operations. Increasing the size of the drums varies the amount of pucker in the face. The bias buff can be adapted to various con- toured parts and degrees of cutting and coloring. An advantage of the "Iris"-made buff is the elimination of material beyond the inside diameter to the arbor hole. Thus, more of the cloth is available for use. Ventilated Bias Buffs Although the puckered characteristic of bias buffs results in cooler running, some operating conditions require additional cooling. Steel centers with holes and ridges are designed to collect and divert more air. The air cools the buff and the work- 37