| 摘要 |
A depth limiting device includes a stop collar having a an open end portion and an workpiece engaging portion extending along the open end portion thereof for contacting a workpiece; a spindle extending axially through the shell, the spindle including a first end extending from the exterior of the stop collar for attachment to a hole forming apparatus, and an second end interior to the stop collar for attachment to a hole forming bit, wherein the attached hole forming bit projects through the open end portion of the stop collar at a predetermined length corresponding to the desired depth of the hole in the workpiece; and a bearing assembly operatively associated with the stop collar and the spindle for isolating the rotation of the spindle from the stop collar whereby the stop collar ceases to rotate when contacting the workpiece without generating sufficient frictional contact to mar or otherwise damage the workpiece.
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