7 Common Torque Testing Mistakes (And How to Avoid Them)

Mistake #1: Testing Too Few Samples

If you’ve ever stood on a production floor watching cases stack up, you know the pressure: “Just test a couple and release it.” The problem is that torque isn’t a single number. It’s a distribution.

When you only test 1–3 bottles, you’re not doing quality control—you’re flipping a coin with better packaging.

Here’s what that looks like in real data. Test 3 bottles and you might get 2.0, 2.1, 2.0 N·m (Mean = 2.03 N·m) and everything feels safe. Then you finally test 20 bottles and discover Mean = 2.15 N·m with CV = 12%. Same line, same day—completely different risk picture.

My rule in a QC lab is simple: if you want *statistics*, you need a real sample size. Test 10–30 bottles per batch (minimum 10 if you’re calculating Mean/SD/CV). The NLY-20A makes this painless because it auto-calculates Mean, SD, and CV—no spreadsheets, no manual math.

And yes, it costs you a couple minutes. But catching a drift early can save $10,000+ in rework, customer complaints, or a batch recall.

Mistake #2: Re-Testing the Same Bottle

The error: Testing the same bottle 3 times to "verify" the reading.

Why it's wrong:

• The cap liner deforms after the first test

• Removal torque decreases by 10-20% on the second test

• You're not testing the product—you're testing a damaged cap

Example:

• First test: 2.0 N·m

• Second test (same bottle): 1.7 N·m

• Third test (same bottle): 1.5 N·m

> 💡 Lab Manager's Note: "I once watched a junior technician re-test a failing bottle three times, hoping the number would eventually fall into spec. I had to explain that physics doesn't care about hope—once you've compressed that liner, the seal integrity is gone. Trust the first number, or get a fresh bottle."

Exception: Re-testing is acceptable for troubleshooting (e.g., diagnosing operator technique), but not for release testing.

Mistake #3: Testing at the Wrong Temperature

Temperature is the silent saboteur of torque testing. The instrument can be perfectly calibrated, the operator can do everything “right,” and your numbers still drift—because the sample never stabilized.

Hot caps expand, friction changes, liners soften. Cold caps contract, threads bite harder, and torque spikes. The swing is not subtle: it’s common to see ±15% variability just from temperature.

If you test a hot-fill bottle at 40°C you might read 1.8 N·m, then later the same product at 23°C reads 2.1 N·m, and if you pull it from cold storage at 5°C it can climb to 2.3 N·m. If you don’t control temperature, you’ll end up adjusting the capping machine to chase noise.

Best practice: test at 23°C ± 2°C, and for removal torque, wait 24 hours after production so the liner can relax and the package can reach equilibrium. If you must test outside room temperature (for troubleshooting), record the sample temperature alongside the torque value.

Pro tip: The NLY-20A’s sensor can be temperature-compensated, but the cap material is not. Control the sample, not just the tester.

Mistake #4: Inconsistent Operator Technique

The error: Different operators get different readings on the same bottle.

Why it's wrong:

• Twist speed affects peak torque (too fast = inertial spike, too slow = friction creep)

• Grip pressure deforms the bottle neck

• Hand position introduces side loads

Example:

• Operator A (fast twist): 2.3 N·m

• Operator B (slow twist): 1.9 N·m

• Operator C (squeezes bottle neck): 2.5 N·m

> 💡 Lab Manager's Note: "We call it the 'Death Grip.' I see operators squeezing the bottle neck so hard while twisting that they actually ovalize the finish. If you see your knuckles turning white, you're doing it wrong. Support the base, don't choke the neck."

Verification: All operators should get within ±5% of the target value on the reference bottle.

Mistake #5: Ignoring Calibration

The error: "We calibrated the tester 3 years ago, so it's still good."

Why it's wrong:

• Torque sensors drift over time (0.1-0.5% per year)

• Shock damage (dropping, overtorquing) can offset the zero point

• Uncalibrated testers fail GMP/ISO audits

Example:

• Year 1: Tester reads 2.00 N·m on a 2.00 N·m standard ✅

• Year 3: Tester reads 2.08 N·m on the same standard (4% drift) ❌

• Result: You're rejecting good product (false rejects)

The fix:

• Annual calibration with ISO 17025 traceable certificate (mandatory for GMP/ISO)

• Weekly verification using standard weights (hang 1 kg at 20 cm → should read 1.96 N·m)

• Immediate recalibration if the tester is dropped or shocked

NLY-20A advantage: On-site calibration capability (no 2-week downtime for factory return).

Mistake #6: Testing Application Torque Instead of Removal Torque

The error: Measuring torque during capping and assuming that's what the consumer will experience.

Why it's wrong:

• Application torque ≠ removal torque

• Liner compression, thread relaxation, and internal pressure change the torque over time

• Hot-fill bottles: Removal torque is 20-30% higher than application (due to vacuum)

• Carbonated bottles: Removal torque is 20-30% lower than application (due to CO2 pressure)

Example (hot-fill juice):

• Application torque (at capping): 2.0 N·m

• Removal torque (24 hours later): 2.5 N·m

• Consumer complaint: "Cap is too tight!"

The fix:

• Test removal torque for consumer experience (wait 24-48 hours after capping)

• Test application torque for capping machine verification (test within 5 minutes)

• Use the NLY-20A's dual modes: "Opening Force" (removal) and "Locking Force" (application)

Mistake #7: Choosing the Wrong Torque Range

The error: Buying a 20 N·m tester for 1 N·m samples (or vice versa).

Why it's wrong:

• Testing at <20% of Full Scale (FS) gives poor relative accuracy

• Example: 1 N·m on a 20 N·m tester = ±10% relative error (too high for QC)

• Testing above FS damages the sensor

Example:

• Pharmaceutical vials: 0.8-1.2 N·m

• Wrong choice: 20 N·m tester (relative error = ±10%)

• Right choice: 5 N·m tester (relative error = ±2.5%)

The fix:

• Choose a range where your samples fall in the 40-100% of FS

• For diverse products, buy multiple testers (e.g., 5 N·m for vials, 20 N·m for bottles)

• See our [Buying Guide](/resources/torque-tester-buying-guide-range-selection) for detailed range selection

Bonus Mistake: Not Documenting Your Data

The error: Handwriting torque values in a notebook.

Why it's wrong:

• Handwritten logs are prone to transcription errors

• No traceability (auditors can't verify authenticity)

• Can't calculate statistics (Mean, SD, CV) without manual math

• Fails 21 CFR Part 11 (electronic records requirement for pharma)

The fix:

• Use the NLY-20A's electronic data logging (200 test groups, 2,000+ individual tests)

• Export to CSV for LIMS integration

• Print test tickets with the built-in printer (optional)

• Maintain audit trail (timestamp, operator ID, batch number)

How the NLY-20A Prevents These Mistakes

Mistake #1 (Too few samples)

• ✅ Stores 200 samples per test group

• ✅ Auto-calculates Mean, SD, CV (no manual math)

Mistake #2 (Re-testing)

• ✅ Peak Hold mode captures true maximum on first test

• ✅ Audio alert confirms peak capture (no need to re-test)

Mistake #3 (Wrong temperature)

• ✅ Temperature-compensated sensor

• ✅ Reminder to test at room temp (configurable in settings)

Mistake #4 (Inconsistent technique)

• ✅ 4-post fixture prevents tilting

• ✅ Visual guide for proper hand position

• ✅ Operator training mode (compares to reference bottle)

Mistake #5 (No calibration)

• ✅ On-site calibration capability (dead weight kit)

• ✅ Calibration reminder (configurable interval)

• ✅ ISO 17025 traceable certificate

Mistake #6 (Wrong test mode)

• ✅ Dual modes: Opening Force and Locking Force

• ✅ Clear on-screen labels (no confusion)

Mistake #7 (Wrong range)

• ✅ Available in 5, 10, 20, 40 N·m ranges

• ✅ Free consultation to choose the right range

Bonus (No documentation)

• ✅ Electronic data logging (21 CFR Part 11 compliant)

• ✅ USB export to CSV

• ✅ Built-in printer (optional)

Summary: The Real Cost of These Mistakes

Conclusion

The 7 mistakes:

1. Testing too few samples → Test 10-30 bottles

2. Re-testing the same bottle → Use fresh bottles

3. Testing at wrong temperature → Test at 23°C ± 2°C

4. Inconsistent operator technique → Standardize training

5. Ignoring calibration → Annual calibration + weekly verification

6. Testing application instead of removal → Test both, but know the difference

7. Choosing wrong range → Match range to your application

The NLY-20A prevents all 7 mistakes with built-in safeguards, auto-statistics, and electronic data logging.

Next steps:

1. Audit your current torque testing process against this checklist

2. Identify which mistakes you're making

3. Implement the fixes (or upgrade to NLY-20A)