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00:00This is a ratcheting click type torque wrench. It's the most commonly used torque
00:05wrench available. In this video we'll take a close look at the mechanism inside
00:10to see how it works. Before we jump into the inner workings of a torque wrench
00:14let's first understand how it is used and what are the key components involved.
00:19Let's get started. Torque is a rotational force. It is usually measured in foot
00:24pounds inch pounds or Newton meters. A torque wrench is a specialized socket
00:30wrench tool designed to tighten fasteners to a predetermined torque value
00:34ensuring consistency and preventing over or under tightening of the fasteners
00:39which can lead to issues like strip threads or loosening. Using a torque wrench
00:45to loosen fasteners can potentially damage the tool and affect its accuracy.
00:50Torque wrenches have a maximum torque rating and using them to loosen
00:54fasteners might subject them to forces beyond their intended capacity. As you
00:59are tightening a fastener you'll hear and feel a distinct click when the preset
01:04torque level is reached. This lets you know it's time to stop applying force
01:09preventing over tightening. The handle is where you grip the wrench during use and
01:15it's also used for setting the desired amount of torque you want to apply to a
01:19fastener. The torque main scale is engraved on the wrench body with more
01:25precise subdivision markings on the handle for micro adjustments. There's a
01:30spring-loaded locking ring used to secure the set torque value preventing
01:35accidental changes during use. Torque setting can be adjusted by first
01:40depressing the locking ring and turning the handle to the desired torque setting.
01:45Turning the handle clockwise will increase the torque value and turning it
01:49counterclockwise will lower it. When the desired torque level is set the
01:54locking ring can be released to lock the handle. If for example you want to set
02:00the torque value to 32 inch pounds, turn the handle until its top edge is even
02:05with the horizontal 30 mark on the main scale and the zero mark on the handle
02:09lines up with the vertical line of the main scale. Then turn the handle clockwise until
02:15the two mark lines up with the vertical line of the main scale. The torque value is now set to 32 inch pounds.
02:24This is the ratchet head. It allows the wrench to turn the fastener in one direction while preventing
02:30rotation in the opposite direction without having to lift and reposition the wrench for every turn.
02:36The direction of rotation can be changed by moving the selector level on the back
02:41of the ratchet head. This is the square drive. This is where interchangeable
02:46sockets that correspond to the fastener size are mounted. The most common drive
02:51sizes available are 1 quarter, 3 eighths and half inch. The sockets are held in
02:56place by a ball detent mechanism. In this example the ball is spring-loaded.
03:01Let's take a look at the ratchet head mechanism. It typically consists of a gear and a set of
03:07balls. The square drive is attached to the gear that can rotate in both directions and the
03:13balls are the two small spring-loaded levers opposite of each other that engage with the gear
03:18teeth. Only one ball can engage with the gear at any given time. The lever controls
03:24which ball is in contact with the gear, determining the direction in which the ratchet mechanism operates.
03:31When engaged, each ball wedges itself against the gear teeth, preventing rotation in one direction,
03:37but the ball can slide over the teeth in the other direction creating the clicking sound you hear when using the ratchet.
03:45Now let's take a closer look at the click mechanism inside the torque wrench.
03:50Right below the ratchet head mechanism there is a pin that holds the head assembly to the wrench body which is a hollow metal tube.
03:57The pin allows the head assembly to pivot inside the wrench body.
04:01At the end of the head assembly there is a slot where a pivot block makes contact.
04:06On the other side of the pivot block is a spacer with another slot also in contact with it.
04:12The spacer and pivot block are compressed by a large adjustable spring.
04:17Turning the handle changes the tension on the spring via a screw thread.
04:22This compression stores potential energy in the spring.
04:25When the preset torque amount is reached, the force generated by the spring on the pivot block is overcome.
04:31The energy stored in the system is released, causing the block to momentarily disengage and tilt.
04:38Simultaneously, the end of the ratchet head assembly hits the inside wall of the wrench body, producing the audible click sound.
04:46After the click, nothing prevents the user from adding additional torque.
04:50Consequently, clicked torque wrenches are not 100% safe from over-torquing.
04:55It is recommended to set the torque wrench to its lowest level before storing the torque wrench for a long period of time.
05:01This releases the tension on the internal spring and prevents creep, which is a slow deformation when subjected to persistent mechanical stress.
05:11But how do you keep the handle locked during use?
05:14There's a series of grooves on the wrench body along the travel path of the handle.
05:19Hidden under the locking ring, there are five holes along the circumference of the handle body.
05:24There's a ball captured in each hole.
05:27The locking ring is maintained in the lock position by a spring.
05:30When the locking ring is at the lock position, the balls get forced into the grooves they are aligned with, keeping the handle from rotating.
05:39When you pull the lock ring, there's an additional clearance above the balls and they are free to disengage and slide over the grooves, allowing rotation off the handle.
05:49I hope you found this video informative and interesting.
05:52If you did, don't forget to give it a thumbs up and subscribe.