HSS Ridgbor Extension Bits will cut through Metal lath, Nails, Knots, and "Hard Woods" easily. These bits are made of the same steel used in bits manufactured for production cutting of tough metals.
The STRAIGHT SHAFT SERIES are manufactured with a 135° Split Ponit and are the same diameter the entire shaft (these are basically aircraft extension bits with a bright, polished silver finish).
The REDUCED SHAFT SERIES are an exclusive bit that has been a favorite amongst experienced journeyman for over 3 decades. They are made with a slightly deeper angle (118° standard point) and undergo a machining process which makes this bit unlike any other bit on the market. The unique difference between the reduced M1-Ridgbor° and other HSS extension bits is the secondary machining process. The Reduced M1-Ridgbors are machined down, all the way into the bottom of the flute allowing 100% chip clearance and smooth, non-binding penetration. Especially suitable for drilling through both metal and wood (including nail embedded wood).
NOTE: The STRAIGHT SHAFT SERIES and M1-RIDGBOR REDUCED SHAFT SERIES are made by two different USA manufacturers for the Service Warehouse.