Bush bearing

The essentials

A bush bearing consists of a cast iron body (often called a block or pedestal) with a bored hole into which a cylindrical bush of gunmetal or brass is pressed. The shaft passes through the bush, so it must be inserted endwise. The body has a base with holes for bolting it to a frame or foundation. When the bush wears out, it is pressed out and replaced, while the body is reused.

Key points

• Main parts: body (with base and boss), bush, and a locking device such as a set (grub) screw.
• The bush often has a flange or collar at one end that bears against the face of the body and stops axial movement in one direction.
• A grub screw, snug or dowel is used to stop the bush from rotating inside the body.
• An oil hole is drilled through the top of the body and the bush so that lubricant reaches the shaft.
• Holes in the base may be elongated (slotted) to allow small adjustments in alignment while fixing.
• Disassembly drawing: body and bush are shown separately, each with the necessary views and dimensions.

Exam tips

• In the sectional assembly, show the oil hole passing through both body and bush, and hatch the two parts in opposite directions.
• Show the grub screw unsectioned even when cut by the cutting plane.

Common mistakes

• Forgetting the oil hole in the bush.
• Hatching the shaft or the screw in a longitudinal section.