Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Jim, may I guess that the burr is at the inside top of the crosshead guide channel, as though you drilled and tapped to mount an oiler?

Do you have any hooked dental tools or other similar angled pieces of metal, that will fit down in the hole and impinge on the bottom of the threads you have made?

Other than such a tool as that, then perhaps you can address and dress the very bottom threads in that hole with the very tip of a jeweler's rattail file worked around the hole all the way, being careful not to bugger the threads at the top of the hole any more than can be helped!?!?