1. A CUTTING HEAD FOR CONNECTING WITH SQUARE DRIVING MEMBERS ON OPPOSITE SIDES CONSISTING OF AN ANNULAR BODY A SERIES OF SPACED BIT HOLDERS AROUND AT LEAST ONE END OF SAID ANNULAR BODY, CUTTING BITS MOUNTED IN SAID BIT HOLDERS, A HUB SUBSTANTIALLY AS LONG AS SAID ANNULAR BODY COAXIALLY CONCENTRIC WITH AND SUPPORTED IN SAID ANNULAR BODY, SAID HUB HAVING A SQUARE DRIVING BORE THERETHROUGH, CONVEYOR FLIGHTS OF PREDETERMINED HAND CONNECTING SAID HUB WITH THE INTERIOR OF SAID ANNULAR BODY TO SUPPORT THE LATTER, SAID HUB HAVING SPACED LOCKING PINHOLES RADIAL TO SAID SQUARE DRIVING BORE AND ADJACENT EACH END OF SAID HUB TO CONNECT SAID SQUARE DRIVING BORE TO SQUARE DRIVING MEMBERS FOR FACING THE BITS IN SAID HEAD IN EITHER DIRECTION.