M1-Ridgbor° Extension Bits These bits will cut through Metal lath, Nails, Knots, and "Hard Woods" easily. Most bell hangers are made of carbon tool steel, suitable for wood only. The Ridgbor is made of the same M-1 steel used in bits manufactured for production cutting of tough metals. The unique difference between the reduced series M-1 Ridgbor° and other HSS extension bits is the secondary machining process. The 3/8" M-1 Ridgbor is machine lathed down to 5/16", all the way into the bottom of the flute allowing 100% chip clearance and smooth, non-binding penetration. Especially suitable for drilling in nail embedded wood, the Ridgbor does not have a wire pull hole.
NOTE: The 1/4" reduced shaft Ridgbors are machine lathed to 15/64". The 3/8" Ridgbors are lathed to 5/16" and the 1/2" Ridgbors are lathed to 3/8". For the 3/4", these particular Ridgbors are reduced to 1/2" Shaft, not lathed.