Like ketchup bottles, wheel nuts always appear to be either too narrow or too loose. Too loose when it comes to wheel nuts and you may create a mess or lose a wheel; too tight, and you may need to grill pliers or break something. Unfortunately, most DIYers seem to be mistaken on the “tighter is better” side, resulting in frustration, broken bolts/threads, and even harm.
For comfort, repeatability, consistency, and safety, technicians indicate how much fastener compression is required for each cap (yes, there is a specification for ketchup bottle cap torque), screw, bolt, nut, sensor, and spark plug. Each DIYer requires to know how to use a torque wrench in the toolbox with at least one or two.
What’s a Wrench Torque?
Torque is a significant metric for understanding when it comes to both opening ketchup cans and tightening wheel nuts. Torque is an indirect measure of the amount of compression exerted by the bottle cap or wheel nut on the bottle or hub, wheel, and brake rotor. We’re saying “indirect” because there’s no practical way of measuring compression or how much the bolt extends, but what’s “torque,” anyway?
Torque is a twisting force metric, typically expressed in lb·ft, lb·in, or N·m (pound·foot, pound·inch, newton·meter), which is the range of force moments. Imagine removing wheel nuts with a 2-foot breaker bar to visualize this. With the socket placed on the wheel nut, applying 50 lb of force to the end of the breaker bar outcomes in a torque of 100 lb·ft on the wheel nut, that is, a force of 50 pounds multiplied by 2 feet of the lever. You would only need 33.3 lb of force to get 100 lb·ft of torque with a 3-ft breaker bar, while a 1-ft ratchet would need 100 lb of force.
Because humans were not produced in their hands with calibrated force meters, there is no way to continuously assess how much force you put on a wrench and how much torque you placed in a nut or bolt. A calibrated torque wrench is precisely what you need to guarantee that everything from oxygen sensors and spark plugs to cover gasket bolts, wheel nuts, and cylinder head bolts is properly tightened.
What are the Types of Torque Wrenches?
There are several kinds of torque wrenches available depending on the application— but three of them are most common in the automotive sector, including beam, click, and digital torque wrenches. Each sort operates slightly differently in order to measure correctly how much twisting force you apply to a particular fastener.
Beam-type torque wrenches were invented about a century ago and are the simplest and easiest to use. The primary beam is fitted with a handle that you use to force the socket. The indicator beam is attached to the head of the socket and does not move when a fastener is tightened. The gage on the primary beam measures the distance it is deflected, which gives you a reading of the torque.
Click torque wrenches look more like normal ratchets, although they have unique inner torque measurement systems. The micrometer adjustment that compresses a spring inside is the most prevalent. The spring is pressing a ball or cube that lies in the head in a detent. The ball or cube moves out of the detent when the defined torque is achieved, making a clicking noise. The tighter the spring, the more difficult it will be to move the ball out of the detent.
The electronic torque wrenches do not have moving components using a piezo-electric sensor that changes resistance depending on how much it deforms. They sense electronically how much twisting force is applied to the socket, providing a digital display reading. The screen can generally be set to blink, vibrate, or beep when reached to set a given torque. A torque-angle feature may also be included in electronic kinds.
For tightening or loosening, beam torque wrenches do not ratchet. Most click-type torque wrenches are ratcheting and can be used to tighten or loosen, although some only allow tightening torque to be applied. Torque wrenches of the beam and click type can be used for loosening, but exceeding the specified maximum torque can harm the wrench. Split-beam torque wrenches should be used only for tightening, as loosening can cause wrench harm.
What is the Torque Wrench Sizing?
The first thing you need is a torque specification to use a torque wrench correctly. The repair manual contains torque requirements, but not generally in the owner’s handbook. The torque wrench you choose depends on the specification of the torque— you wouldn’t be using a small pound·inch torque wrench on a wheel nut and you wouldn’t be using a big pound·foot torque wrench on valve cover bolts.
Small torque wrenches
Varying from 10 to 250 in·ft, are helpful for valve covers, throttle bodies, transmission valve bodies, certain intake multipliers, and internal fasteners.
Medium torque wrenches
For motor accessories, suspension parts, brake parts, interior parts, and some wheel nuts, medium torque wrenches ranging from 5 to 100 lb·ft are helpful.
Large torque wrenches
For cylinder head bolts, significant parts, wheel nuts, and wheel bearing hubs, large torque wrenches ranging from 20 to 250 lb·ft are helpful.
How to Use a Torque Wrench Properly?
Any torque wrench needs a constant and firm hand. If there is a torque sequence, such as tightening wheel nuts, cylinder head bolts, and some inner engine and transmission components, closely follow the measures to avoid harm and guarantee correct operation. Some fasteners, such as cylinder head bolts torque-to-yield, involve further measurement beyond twisting force. An extra angle will be defined after the bolt is set to a given torque, turning the bolt further, regardless of torque. Sometimes you can use paint marks, but more precise are torque-angle gauges and electronic gauges.
Watch the gage closely until it reaches the necessary torque to use a beam torque wrench, then stop applying force to the handle. To use a torque wrench click-type, whether it is spring or split-beam, change the button and lock it into the necessary torque specification, then tighten the fastener gradually. You will feel and hear a “click” in the handle when the torque limit is reached, at which point you stop applying force.
Similar to click-types, electronic torque wrenches are used, except that the adjustment and notification is electronic. When torque is reached, indicated by a beep, vibration, or flashing light, stop applying force to prevent the fastener from being over-tight.
Split-beam and beam torque wrenches need no unique storage care, but click-type micrometer-adjust torque wrenches should be removed. This will discourage future torque measurements from “setting” and skewing the spring. In their protective instances, torque wrenches should be stored and never dropped. You should calibrate your torque wrench about once a year to maintain it within tolerances.
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