A center for maintaining a cutting tool, such as a tapping tool or reamer, in axial alignment with a hole to be worked upon, said center comprising:
- an elongated body having two opposite ends, one of said ends adapted to be mounted within the holding device of a machine tool positioned in registry with the hole to be worked upon, the body defining an elongated cavity opening out of the other end of said body and including a slot extending along a side of said body and in communication with said cavity;
- an elongated centering pin having a tipped shank which is positioned within said elongated cavity so that the tip of said shank is directed generally out of the cavity for cooperatively engaging the cutting tool with which the center is to be used, said shank being positioned within said cavity for sliding movement longitudinally of said body between an extended position at which a substantial portion of said pin extends out of said cavity and a retracted position, said centering pin including an accessible handle joined to said shank and extending through said slot, said handle cooperating with said slot so that as said centering pin is guided along said cavity, the handle is guided along said slot;
- biasing means interposed between said centering pin and said elongated body for biasing the centering pin shank from the retracted position toward the extended position;
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- said body slot having an elongated section extending linearly along one side of said body and parallel to the longitudinal axis thereof and an L-shaped notch joined to said elongated slot section at an end thereof opposite said other end of said body, said L-shaped notch having two leg portions forming a right angle with one another, one leg of said L-shaped notch being joined to said elongated slot section so as to form substantially a right angle therewith and the other of the notch legs being oriented substantially parallel to the elongated slot section and directed from the one notch leg generally toward said other end of said body;
- said handle being slidably movable relative to said body through the elongated slot section for moving the centering pin axially through the body cavity between the extended and retracted positions, being slidably movable relative to said body through said one leg of said notch for rotating the centering pin within the body cavity between a first position at which the handle is positioned at the end of said slot section opposite said other end of said body and a second position at which the handle is offset to one side of said elongated slot section, and being slidably movable relative to said body into and out of said other leg of said notch for axially shifting the centering pin through the body cavity between said second position and a locked position at which the handle cooperates with said other leg to prevent the centering pin from rotating within the body cavity and returning to the extended position, the L-shaped notch being disposed along the length of the body so that upon manipulation of the handle from the elongated slot section and into said other of the notch legs through said one notch leg, the centering pin is releasably locked in a retracted position against the biasing force of the biasing means and prevented from returning to the elongated slot section;
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- said centering pin shank including an end section providing the tip of said shank and another section to which said handle is connected so that the rotation of said another section relative to said body is prevented when said handle is positioned in the elongated section of said slot or the other leg of the slot notch, and said end section is journaled to said another section so that when the tip cooperatively engages a cutting tool and the cutting tool is rotated, the end section is permitted to rotate with the cutting tool.