Torque Wrenches

Richard L. Parish  |  5/12/2006 5:30:57 PM

Figure 1. Exposed pointer type torque wrench.

Figure 2. Clicker type torque wrench.

Figure 3. Detail of scale on exposed pointer type torque wrench.

If you plan to do much work on lawn/garden or grounds maintenance equipment, you need a torque wrench. Even a job as simple as changing a spark plug on a small engine should be done with a torque wrench.

What Is a Torque Wrench?
A torque wrench is a socket wrench handle that indicates the torque applied to the socket when the wrench handle is rotated.

Types of Torque Wrenches
There are two types of torque wrenches. The exposed pointer type has a long pin that remains straight as the handle flexes under torque load. An arc-shaped scale on the handle moves under the pointer and allows a direct reading of the torque as indicated by the pointer. The clicker type has an enclosed mechanism. These wrenches have a micrometer-type adjustment on the end of the handle where you can set the desired torque. When the desired torque level is reached, an audible “click” is heard – and felt. The clicker type is more common and somewhat easier to use – especially when the top of wrench is not readily visible. On the other hand, the clicker type only tells you when you reach the preset torque; it does not allow you to measure torque. The clicker type torque wrench normally has a ratchet head, but the exposed pointer top does not, thus the clicker type is faster to use.

Uses for a Torque Wrench
It is important to use a torque wrench to install spark plugs in small engines. Many small engines have aluminum heads. Aluminum is relatively soft compared with the steel threads on spark plugs. If the plug is overtightened, the threads can easily be stripped out. If the spark plug is not adequately tightened, engine compression can blow the plug out – also damaging the threads. Wheel bolts and blade attachment bolts are other critical areas where correct tightening torque is important. Operator’s manuals and service manuals should give recommended torque values.

Good torque wrenches are expensive – and worth it for professional mechanics. You can expect to pay at least $75 for a good torque wrench, and some cost much more. If you only need a torque wrench occasionally, you can pick up a ½” drive clicker type wrench for under $20 that will be adequate.

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