| 摘要 |
A boring bar assembly having a symmetrical carbide tip holder for turning a brake drum and which can be rotated 180 degrees for facing either or both sides of a rotor of a disc brake. A hexagonal bar provides a housing for receiving a depth of cut mechanism including a dial at one end of the bar. A movable dial rod is connected to the dial mechanism and extends through the housing and engages a tool bit holder at the other end of the bar. A carbide tip is positioned and clamped in one of two undercut pockets on opposite sides of the flat head of the bit holder. The holder includes an angular surface engaging the dial rod so that the holder is moved toward and away from the axis of the housing in response to the dial rod. A spring-loaded tool retractor is provided in a bore of the housing and includes an angular end surface which is yieldably urged against a portion of the angular surface of the holder. When the dial rod is retracted and moved away from the holder, the end surface of the retractor slides along the angular surface of and into the holder which retracts the holder toward the axis of the housing.
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