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All about Torque Wrenches

6/5/2015 10:59:40 AM | by Buttercup


A torque wrench is a wrench tool mainly used in fastening nuts or bolts using an applied torque. It was invented and designed to avoid over tightening of bolts whenever steam pipe and water main underground repair is being done. It has internal mechanism which is usually in the form of socket wrench. It helps the operator measure an accurate torque being applied to the fastener to meet the required application’s specification. It is used to achieve a proper loading and tension of all parts.

Types of Torque Wrenches

Beam Type
The Beam Type torque wrench is made of elastic material which bends in response to the torque applied. It is the simplest form of torque which consists of the wrench head, handle, and a long lever arm. The handle has a deflection wherein it is proportional to the torque being applied and the cantilever arm’s constants. It also includes a smaller bar with an integral mechanical indicator which only maintains a constant position with respect to the wrench head. The indicator will move when a torque is applied until it reaches the desired torque.

Click Type
The Click Type of torque wrench presents a more classy method of torque application using a calibrated clutch mechanism. This form uses a spring preloaded by a screw thread and a ball detent that transmits force until it reaches the preset torque. The ball will click out of its socket when the spring overcomes the force that is exerted. This wrench is designed to have a greater precision at the set point as its advantage.

Slipper Type
The Slipper Type avoid the over tightening of the fasteners using a continuous pressure and rotation that is applied.

Deflecting Beam Type
The Deflecting Beam torque wrench is employed by applying torque to a deflecting beam. It has dual signal which provides a consistent and accurate reading as well as the safety margin on maximum loading. This signal can be seen and heard upon reaching the selected torque.

Electronic Torque Wrench
The Electronic type torque wrench or digital torque wrench uses a strain gauge that is attached to the torsion rod as its measuring part. A signal is generated and converted to the required torque and will be shown on the digital display. It can store the measurement details and permanently displayed during the tightening process.

Mechatronic Torque Wrench
The Mechatronic Torque Wrench is the combination mechanical and electronic measurements. It functions like the click type of torque and the measured value will be presented on the digital display.

“No-hub” Wrench
The “No-hub” Wrench is designed to tighten the clamping bands on “hubless” soil pipe couplings. This wrench used by plumbers consists of a T-handled wrench with the combination of clutch and ratchet. It is regulated to achieve a torque needed to seal the coupling.

Guidelines in Torque Wrench Calibration

Proper Torque Calibration should be done annually to ensure a reliable performance. The following are some of the methods on how to calibrate a torque wrench.

• Weight Calibration
1. Mark the center of drive on the back of the wrench.
2. Using a tool, measure from the mark going through the hand’s position and make a second mark. Take note of the distance between two marks.
3. Be sure to locate only the square head in a bench vise and move the handle into a horizontal position.
4. Align the torque value to the setting of the distance that you got in step 2 multiplied it to 20 pounds.
5. Hang a weight of 20 pounds on the mark you did on step 2
6. A click from the tool will be heard, lift the weight and move it to the head of the wrench until it stops to click.
7. Measure the distance between the click mark and the square head. Multiply it by 20 pounds to get the true amount of torque.
8. Substitute the given numbers to the formula Ta=Ts x (D1/D2) wherein Ta is the torque applied, Ts is the Torque setting, D1 for the 1st distance and D2 for the last distance you found.
9. Do accurate calculations and adjust the wrench accordingly.

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