I started out using a 2 1/2" boring bar 16" long with no end support. It was easy to retract the table and measure the hole for size that way, but I had chatter problems on lighter cuts no matter how I dressed the tool bit. We later switched to the over arm support and had much better finish results with cutting RPM and feed rate being able to be increased. Cutting time was shorter but it took just a little longer doing the measuring. This is how we finished the job. The customer wanted a metal to metal size fit, Pin to Hole. He is a heavy equipment contractor and said while clearance for easy assembly is the standard, the holes wear to excess in a much shorter time. Most heavy equipment owners will ask for manufacturer machine fit specs., or something like that oversize for ease of assembly.