Abstract: A coupling mechanism interconnects a rotatable connecting end of a support on a broaching machine and a bit holder which includes a rotary hollow shaft and a mandrel received in the hollow shaft. The coupling mechanism includes a first coupling member that has a first disk part and a first neck part, and a second coupling member that has a second disk part and a second neck part. The first neck part is connected to the connecting end of the support. The first disk part has a plurality of posts projecting axially from the first disk part opposite to the first neck part. The second neck part extends into the hollow shaft for connection with the mandrel. The second disk part has slide holes which extend axially in the second disk part at locations radially outward of the second neck part so as to receive the posts. The second coupling member is guided by the posts and the slide holes for sliding axially relative to the first coupling member.