I happen to have a nice Nikken metric boring head that was designed to fit a26mm BT-flange holder. This boring head has a 26mm dia x 26mm straight cylindrical shank with two radial holes at 90-deg to accept locking set screws or pins.
Of course, my mill doesn't have a BT spindle; it has an R8 spindle. So my idea was to use an end mill holder as an adapter for this boring head. But that presents its own problems as I have yet to encounter a 26mm end mill holder. (Anyone know a source for these? I find it amazing that the US machining industry is still so firmly entrenched in the English system.)
Short of finding a 26mm holder, my next thought would be to buy a 1" end mill holder (25.4mm) and try to modify it to accept the 26mm shank of my boring head. I just don't know how successful that plan might be. For one thing, I suspect that the bore of an end mill holder is hardened and ground, so I will probably have a tough time trying to bore 0.6mm off the inside diameter in my lathe. Another possibility would be to use an abrasive cylinder hone to enlarge the bore of the holder. But that may not be a very accurate operation as I only have the low-cost, sprung-arm hones that are common in auto parts stores.
Any thoughts or advice?