Secure your logs in place while cutting tenons, tapering the log, peeling the bark and more with our Log Lock? Heavy Duty Bundle, including TWO Heavy Duty Log Locks?. These heavy-duty Log Locks? are designed for high production users. The Log Lock? Heavy Duty - LL1545HD can accept logs 1-1/2" to 4-1/2" in diameter. The Log Lock? XL Heavy Duty - LL2580HD can accept logs 2-1/2" to 8" in diameter. Heavy Duty Features: The threading is cut coarser on the handle nut, jam nut carriage bolt STANDARD hardware uses oe" ? 13 UNF (Unified fine thread). UNF is commonly used in machine screw parts HEAVY DUTY hardware uses oe? ? 10 ACME UNF threading is shaped like ^ whereas ACME threading is shaped like a trapezoid. It will take a much greater force to strip this kind of threading The standard 13 UNF is good and works for 80% of customers. The 10 ACME is designed for high production users