No, using a torque wrench to loosen bolts will not inherently cause mechanical failure. Torque wrenches are designed to apply a precise amount of rotational force, and this function is equally safe and effective for both tightening and loosening fasteners. The key is to use the wrench correctly and ensure it’s set to the appropriate torque specification.
Understanding Torque Wrenches: More Than Just Tightening
Many people associate torque wrenches solely with the precise tightening of bolts to prevent over-tightening. This is a crucial function, especially in automotive and aerospace applications where incorrect tension can lead to stripped threads, damaged components, or even catastrophic failure. However, their utility extends beyond just applying a specific torque.
How Torque Wrenches Work for Loosening
A torque wrench operates by measuring the rotational force applied. When you’re loosening a bolt, you are essentially applying an equal and opposite force to overcome the initial tightening torque. Using a torque wrench in this scenario can actually be beneficial.
- Controlled Force: It allows you to apply force in a controlled manner, preventing sudden jerks that could damage the bolt head or surrounding material.
- Feedback: Some torque wrenches provide tactile or audible feedback when a certain torque is reached, which can be helpful even when loosening.
- Preventing Stripping: By applying steady pressure, you reduce the risk of stripping the bolt head or the threads, especially on fasteners that have been in place for a long time or are subject to corrosion.
When Could Loosening with a Torque Wrench Be Misinterpreted?
While the wrench itself won’t cause failure, user error or misunderstanding can lead to issues. The primary concern isn’t the wrench’s loosening capability, but rather the torque setting and the method of use.
Incorrect Torque Setting
If a torque wrench is still set to a high tightening specification when you attempt to loosen a bolt, you might be applying more force than necessary. This could potentially damage the bolt or its threads, especially if the bolt was not originally torqued to that high a setting. Always ensure your torque wrench is set to zero or a very low setting when not actively tightening.
Using It as a Breaker Bar
A common mistake is using a torque wrench like a standard breaker bar, especially for very stubborn bolts. A breaker bar is designed for high leverage and shock force. A torque wrench, particularly click-type models, is a precision instrument. Repeatedly applying excessive force to loosen a seized bolt can damage the internal mechanism of the torque wrench, rendering it inaccurate for future tightening tasks.
Best Practices for Loosening Bolts
To ensure you’re using your torque wrench safely and effectively for loosening:
- Set to Zero: Always return the torque setting to its lowest point or zero after use.
- Gentle Application: Apply steady, even pressure. Avoid sudden jerks or impacts.
- Use a Breaker Bar First: For extremely tight or seized bolts, use a dedicated breaker bar to initially break the torque. Once the bolt begins to turn, you can then use a torque wrench if precise control is still desired.
- Lubrication: If a bolt is difficult to loosen, consider applying a penetrating lubricant and allowing it time to work before attempting removal.
Can a Torque Wrench Go Bad from Loosening?
Yes, a torque wrench can be damaged by improper loosening techniques. If you repeatedly use it to break very tight bolts or apply excessive force, you risk damaging its internal calibration mechanism. This means it might not accurately measure torque when you use it for tightening in the future.
Common Misconceptions About Torque Wrench Usage
It’s easy to fall into the trap of thinking a tool has only one primary function. For torque wrenches, the precision tightening aspect often overshadows its potential for controlled loosening. Many DIY mechanics might not even consider using it for removal, opting for a standard ratchet or breaker bar.
The "Loosening is the Opposite of Tightening" Fallacy
While true in principle, the execution matters. The force required to loosen a bolt is often less than the force required to tighten it to its specified torque, especially if the bolt has been in place for a while and hasn’t been subjected to extreme conditions. However, if a bolt was over-tightened initially, the loosening force might be higher.
When is a Torque Wrench Not the Right Tool for Loosening?
- Seized Bolts: Bolts that are rusted, cross-threaded, or otherwise seized often require significant shock or leverage that a torque wrench is not designed to withstand.
- High-Torque Applications: In heavy machinery or industrial settings, the initial tightening torques can be extremely high. Attempting to loosen these with a standard torque wrench could damage both the wrench and the fastener.
People Also Ask
### Can you damage a bolt by loosening it with a torque wrench?
You can potentially damage a bolt or its threads if you use a torque wrench improperly for loosening. This usually happens if the wrench is still set to a very high tightening torque, or if you apply excessive, jerky force, which is not how torque wrenches are intended to be used for removal.
### Is it bad to use a torque wrench as a breaker bar?
Yes, it is generally bad to use a torque wrench as a breaker bar. Torque wrenches are precision instruments designed for accurate torque application during tightening. Using them for the high, sudden forces associated with breaking loose stubborn bolts can damage their internal mechanism and ruin their calibration.
### How much torque does it take to loosen a bolt?
The amount of torque required to loosen a bolt is typically less than the torque it was tightened to, but this can vary significantly. Factors like thread lubrication, corrosion, and the original tightening torque all play a role. For a bolt tightened to 50 ft-lbs, it might take anywhere from 30 to 70 ft-lbs or more to loosen it.
### What is the difference between a torque wrench and a breaker bar?
A torque wrench measures and applies a specific, precise amount of rotational force, primarily for tightening fasteners to a set specification. A breaker bar, on the other hand, is a long, non-ratcheting bar designed to provide high leverage and shock force for breaking loose stubborn or seized fasteners.
Conclusion: Use Tools Appropriately for Longevity
In summary, a torque wrench is not inherently designed to cause mechanical failure when loosening bolts. However, improper use—such as setting it to a high tightening torque, using it as a breaker bar for seized fasteners, or applying excessive force—can lead to damage to the wrench itself or the fastener. Always prioritize understanding your tools and using them as intended to ensure both mechanical integrity and tool longevity.
For your next project, consider investing in a good quality breaker bar if you frequently encounter stubborn fasteners. This will protect your precision torque wrench for its primary job: accurate tightening.
