This part has been taking up space in a cabinet, and I haven't been able to figure out what it is for. I have a Promaster 2180 lathe and a Vectrax (Bridgeport clone) mill I inherited with this job. The bore in the large end with the stamping on it is tapered to what I believe is MT5. It is not for sale, I just want to know what I am not making use of... Thanks!