Stephen
i have a laser center finder it has a 6 mm shank and will fit any drill chuck i use on my mill drill and cnc mills got from ebay i think it was £50.00 well worth the money
i got a tormach cnc mill about 3 months ago and it has probing on it been playing with it over the weekend can find center of a bore corner of a vice or probe two edges to set a datum at the touch of a button wish i had this back in the 80s when i was setting and programming cnc mills on more edge finders and clocks
Geoff