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In the traditional style of white metal bearing, a cast iron pillow block is assembled as a loose fit around the shaft, with the shaft in approximately its final position. The inner face of the cast iron pillow block is often drilled to form a key to locate the bearing metal as it is cast into place. The ends of the bearing are packed with clay and molten white metal poured into the cavity around the shaft, initially half filling the pillow block. The bearing is stripped, and the white metal trimmed back to the top surface of the pillow block. Hardened white metal is soft enough to be cut with a knife or sharp chisel.
A steel shim is inserted to protect the face of the lower bearing and to space the cap of the pillow block away from the shaft. After resealing the ends with clay, more white metal is then poured to fill the cap of the pillow block through the hole in the top of the pillow block cap that will eventually be a lubrication hole.
The two halves of the bearing are then split at the shim, the oil holes cleared of white metal and any oil ways cut into the surface of the new bearing. The shaft is smeared with engineer's blue and rotated in the bearing. When the bearing is disassembled the blue fills the hollows and is rubbed off the high spots. The high spots are scraped down, and the process repeated, until a uniform and evenly distributed pattern of blue shows when the shaft is removed. The bearing is then cleaned and lubricated, and shimmed up such that the shaft is held firmly but not binding in the bearing. The bearing is then "run in" by being run heavily lubricated at low load and revolution, completing the process of exposing the hard bearing surface. After final adjustment of the shimming, a very reliable and high load capability bearing results.
Before the wide availability of cheap electric motors, power was distributed through factories from a central engine via overhead shafts running in hundreds of bearings of this form.
The expression a "run bearing" also derives from this style of bearing, since failure of lubrication will lead to heat build up due to friction in the bearing, eventually leading to the white metal liquifying and literally running out of the pillow block.
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