Using a torque wrench properly is crucial for mechanics and automotive enthusiasts. One of the most debated topics around torque wrench use is whether you need to reset it to zero after each use. There are good arguments on both sides of this issue. Here we’ll go over the pros and cons so you can make an informed decision about the best way to handle your torque wrench.
The purpose of a torque wrench
First, it helps to understand what a torque wrench does. Torque refers to rotational force or tightness. A torque wrench allows you to tighten bolts and nuts to a precise torque specification by indicating when you’ve reached the target amount of torque. Using the proper torque ensures parts are tightened enough to operate safely without being overtightened, which can cause damage.
Torque wrenches come in different drive sizes and measurement standards. The measurement can be in inch-pounds, foot-pounds, or Newton-meters. Torque specifications are usually listed in a vehicle’s repair manual for various fasteners. Using a torque wrench helps mechanics tighten fasteners to these exact specs.
The argument for resetting to zero
The main case for resetting a torque wrench back to zero after each use is accuracy. When you apply torque to a fastener, the internal mechanism of the wrench shifts. This can throw off the calibration ever so slightly. Resetting back to zero realigns the internal parts to ensure the next reading is as accurate as possible.
Torque wrench manufacturers typically recommend resetting to zero in the instruction materials. This prevents the potential buildup of small inaccuracies over time with continued use without resetting. Even high-quality wrenches can experience some drift from the original calibration if you don’t reset between uses.
Resetting also makes it faster to confirm you have the right torque setting dialed in for the next task. Rather than having to check what the wrench was last set at and make adjustments, you can simply reset to zero and then dial in the new torque spec needed.
Mechanics who want to follow best practices to ensure precision and avoid overtightening or undertightening hardware have a strong case for resetting the dial back to zero after each use. This guarantees each fastener starts with the torque wrench precisely calibrated right from zero.
Benefits of resetting torque wrench to zero
- Maintains maximum accuracy of torque settings
- Realigns internal mechanism
- Follows manufacturer recommendations
- Prevents buildup of small errors over time
- Allows confirmation of proper torque setting
- Promotes precision and avoids over or undertightening
Reasons some don’t reset to zero
While resetting to zero has some valid advantages, there are also reasons some auto technicians don’t make a habit of resetting their torque wrench back to zero constantly.
It takes extra time and steps to reset to zero after every single use before putting the torque wrench away. Some techs feel this time adds up and cuts into productivity. The time spent having to re-dial the torque setting for the next use also adds up.
If you’re working on a project where you have to tighten multiple fasteners to the same torque spec, resetting after each one would definitely take more time. You’d have to reset to zero and then redial the needed torque between each fastener.
Some automotive experts argue that constantly resetting to zero is unnecessary in many everyday circumstances. They claim the small potential loss of accuracy from not resetting is negligible on most jobs. As long as you check calibration periodically and make adjustments as needed, accuracy remains dependable for all but the most precision work.
Leaving the wrench set between uses can also serve as a reminder of the last torque setting used. This can prevent mistakes if you need to retighten fasteners or use the same torque spec again soon.
Reasons for not resetting to zero
- Saves time not having to reset and redial torque
- Unnecessary for many everyday jobs
- Small inaccuracies negligible on most jobs
- Leaves reminder of last torque setting used
Best practices for accuracy
The ideal approach is likely applying a blend of resetting and not resetting depending on the context.
For critical applications where extreme precision is needed, resetting to zero makes good sense. Examples include working on medical equipment, aerospace applications, or jobs where safety is dependent on perfect torque accuracy.
However, for much everyday auto repair, construction, or mechanical work, the small potential inaccuracies from not resetting are unlikely to make a practical difference. As long as you maintain and check calibration periodically, consistently not resetting to zero should not be an issue in most situations.
Get to know the quirks and characteristics of your individual torque wrench. Accuracy can vary across different models and brands. Testing your particular wrench and taking notes on how it behaves will help determine the best practices for that tool.
It also depends on how often you actually use the wrench between calibrations. A hobbyist using a torque wrench once a month can get away with never resetting. But for a professional using torque wrenches daily, more frequent resetting will maintain better accuracy.
Consistently applying the wrong force, whether too much or too little, can certainly cause problems. But for many applications, a small variance of a few inch-pounds either way is not likely to make any noticeable difference.
Use your best judgment based on the job, your skills, the specific torque wrench, and how often it gets used. Consider the pros and cons and look for chances to incorporate resetting as part of overall torque wrench best practices when appropriate.
Signs your torque wrench needs calibration
Regardless of whether you reset after each use or not, periodic calibration checks are a must to keep any torque wrench performing accurately.
Watch for these signs that indicate your torque wrench is due for a calibration check and adjustment:
- You hear unusual sounds when applying torque
- The dial or display doesn’t hold steady
- The dial doesn’t return smoothly back to zero
- Readings feel inconsistent or are way off from expected torque
- Difficulty staying accurate close to upper or lower limits
- It’s been over a year since the last calibration
Torque wrench manufacturers usually recommend getting calibration checked annually at a minimum. For heavy usage under harsh conditions, calibration every 6 months is ideal.
You can do a basic calibration check yourself at home using a lug nut and torque analyzer. Tighten the lug nut to certain torque specs and see if the wrench consistently delivers the expected values. Adjust as needed.
For the most precise calibration, a certified technician at a tool repair shop should handle the calibration. This may involve taking apart the torque wrench, cleaning and lubricating components, replacing worn parts, and methodically adjusting back to OEM specs.
Other torque wrench best practices
Proper usage and care are just as important as calibration when it comes to maintaining accuracy and extending the working life of your torque wrench.
Always double check the manual for model-specific directions. But here are some universal tips for using any torque wrench correctly:
- Choose the right size wrench for the job
- Keep the wrench set around mid-range when not in use
- Pull smoothly in a slow, steady motion without jerking
- Pay attention to the audible click or LED light that signals target torque is reached
- Apply torque perpendicular to the axis of the fastener
- Avoid overtightening once the set torque is reached
- Make sure the wrench is set back to zero after breaking torque
Proper maintenance and storage also helps any torque wrench last longer while staying accurate:
- Wipe clean after each use and store indoors
- Avoid dirt, dust, and moisture
- Lubricate pivot points periodically
- Never use extensions or cheater bars for added leverage
- Store hanging upright or lying flat, not standing on the handle
- Transport carefully to avoid bumps, drops, or falls
DIY torque wrench calibration
With the right tools, you can do a basic torque wrench calibration check at home. This allows more frequent calibration than yearly professional service.
Here’s an overview of the DIY calibration process:
Supplies needed
- Torque wrench
- Torque analyzer
- 7/8″ or 1″ lug nut
- Thin open-end wrench that fits lug nut
Steps
- Secure lug nut in a sturdy bench vise
- Set torque wrench to lowest setting (for click-type) or just above lowest (for dial-type)
- Attach torque wrench to lug nut and pull until click or dial reading
- Loosen lug nut completely and note torque wrench reading
- Attach torque analyzer to lug nut and tighten while noting peak torque
- Compare torque analyzer reading to torque wrench setting
- Repeat process, increasing torque wrench setting incrementally until maximum
- Adjust torque wrench as needed to match analyzer readings
- Recheck accuracy after adjustments before using wrench
This allows you to check torque accuracy throughout the wrench’s range. Make small adjustments to zero in dial or click points until readings align with the known accurate torque analyzer.
DIY calibration takes some care and practice. But it can save on service costs while keeping your torque wrench working like new.
Choosing a torque wrench
With such a wide range of torque wrench types, sizes, brands, and accuracy levels, it can be tricky picking the right one. Here are the main factors to consider for your needs:
Drive size
The drive is the head that attaches to sockets. 1/4″, 3/8″, and 1/2″ drives are common. Choose one that fits the fasteners you’ll be working with.
Range
Make sure the torque range meets your needs. For automotive uses, 25 to 250 ft-lb is versatile. Wider or narrower ranges are available.
Scale
Torque can be measured in inch-pounds, foot-pounds, or Newton-meters. The scale must match your torque specs.
Accuracy
Higher accuracy is better but also costs more. ±3% to ±4% is usually adequate for most mechanics.
Display
Dial or digital readout makes it easy see the set torque. A simple click type works but you must remember the torque setting.
Size
Length affects leverage and comfort. 12″-18″ is common for hand tools. Choose based on the workspace.
Price
Inexpensive click wrenches can run under $50 while pro-grade dial wrenches run over $200. Pay for accuracy you need.
There are also electronic and beam style torque wrenches. Consider the pros and cons of each to pick your ideal type.
Maintaining a torque wrench
Torque wrenches are delicate precision tools that require some care. Proper maintenance keeps them working accurately for years. Here are tips for maintaining a torque wrench:
- Clean after each use and wipe a light oil on metal parts to prevent rust
- Store indoors away from moisture and temperature extremes
- Hang up or keep flat, not resting on its handle
- Check calibration annually or semiannually depending on use
- Lubricate pivot points with light oil
- Protect from drops, falls, or other impacts
- Send for professional service if damaged or very inaccurate
With routine calibration checks and careful handling, a quality torque wrench will provide years of reliable service.
Torque wrench calibration services
While DIY calibration is possible for the dedicated hobbyist, most users should have their torque wrench calibrated professionally on a yearly basis. Here’s what to expect with professional calibration services:
- Performed by trained technicians in metrology labs
- Traceable to NIST standards for highest accuracy
- Often involves fully disassembling the torque wrench
- All components cleaned, adjusted, and lubricated
- Electronically tested at multiple data points
- Calibrated certificate showing accuracy results
- Costs between $20-$60 depending on wrench type
Many tool companies offer warranty and maintenance plans that include annual calibration service. Or you can use an independent metrology lab.
Professional calibration gives you documentation showing the exact accuracy of your torque wrench. This guarantees precision and traceability for the most demanding applications.
Conclusion
Regularly resetting a torque wrench back to zero has valid benefits for precision in critical uses. But for more casual automotive and mechanical tasks, the small inaccuracies caused by not resetting are usually negligible.
Get to know your torque wrench’s quirks through hands-on practice. Combine resetting and not resetting between uses based on your particular wrench, workload, and the precision required.
Annual calibration checks and proper handling are the best ways to keep any torque wrench working accurately for years. Consider DIY calibration between professional service for the most frequent adjustments.
With responsible use and care, your torque wrench will continue delivering reliable and repeatable torque for every fastening job.
