TORQUE WRENCH 101 PROFESSIONAL USER GUIDE WHAT IS TORQUE? Torque is rotational or turning force. Torque is measured in length and force: Length means distance from “center of drive” to “center of handle". Force means “pounds”, “Newtons” etc. TORQUE (Turning Force) FORCE (Pressure Applied) WHAT IS A TORQUE INSTRUMENT? A torque instrument is any device that applies a pre-determined amount of torque to a fastener. Whether it is mechanical or electronic in design, a torque instrument has some type of indicating device which lets the operator know when the correct torque has been achieved: “click” or “impulse-break” feel; sound; lights; gauge; or some combination of these. WHAT IS TORQUE PLUS ANGLE? LENGTH (Distance from pivot point to force) Torque Plus Angle creates a more exact clamp load for torque-sensitive equipment. 300 310 340 350 0 10 20 330 30 320 40 50 250 260 270 280 290 60 70 80 90 100 110 120 Auto manufacturers and makers of other high performance equipment are increasingly specifying HOW DO YOU CALCULATE TORQUE? Torque = Length × Force The standard torque formula used to calculate torque is: “L x F = T" EXAMPLE: 2 ft. (length) x 30 lbs. (amount of force at center of handle) equals 60 ft. lbs. of torque (60 Ft. Lbs.) 240 fasteners with a combination of torque value followed 230 130 140 220 by additional tightening with “angle”, or degrees of 150 160 170 180 190 200 210 wrench turn. Manufacturers can calculate a more exact final “clamp load” for their applications, since “torque & angle” minimizes the impact of thread or 34 u 0 n 35 d 0 er 0 -he 10 ad 20 friction. 330 20 340 350 0 10 3 2 0 0 40 3 330 30 50 320 40 EXAMPLE: Apply 80 ft. lbs. of torque, then apply 90 degrees of rotation 300 310 310 50 70 80 60 240 230 25 2 0 40 260 270 280 290 300 0 250 260 270 280 290 60 WHAT DOES TORQUE DO? 70 80 90 100 110 Torque creates a "Clamp Load" to join two pieces of material. • Bolts (or threaded fasteners), are designed to create clamping force, also called “clamp load”. HEAD FRICTION 90 10 • When torque is applied to a threaded fastener, it draws together the joint, (two pieces of material). • As additional torque is applied to the fastener, the joint is pulled together creating a clamp 0 110 120 45% of Applied Torque 130 140 220 120 1 load as the fastener begins the stretching process. It’s this fastener stretch that creates and 23 150 40 170 180 190 220 1 160 200 210 maintains clamping force, like a stretched bungee cord maintaining tension. 30 • The actual amount of clamp load is determined by several factors: 150 160 170 180 190 200 210 – The amount of torque applied to the fastener. – The material and grade of the fastener. – The external friction on the joint – friction under the fastener head, and friction between the threads of the fastener and material it’s connected to. BOLT STRETCH 10% of Applied Torque THREAD FRICTION Up to 45% of Applied Torque LOAD Distributed over all threads WHY IS APPLYING PROPER TORQUE IMPORTANT? Creating proper Clamp Load prevents damage and equipment failures. • Safety & Performance: Applying accurate torque is critical to assembly applications, engines and precision equipment. • Creating a proper clamp load is the main objective when applying torque to a fastener. Engine cylinder heads, pipe coupling, wheels, all need to be “clamped” uniformly to specific torque values. • There are three main factors that affect the correct application of torque: (1) Condition of components, (2) Accuracy of torque instrument, (3) Properly applied torque values. • Applying torque incorrectly can lead to stripped threads, premature loosening or broken fasteners that can cause catastrophic failure. Leaking joints may cause engine or equipment failures.
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