Torque Wrenches Technical Information
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Basics of... Torque Wrenches
Torque wrenches are generally calibrated from 20% of the maximum capacity to 100% of capacity.
Torque applying wrenches should never be used to remove tightened fasteners. Calibration can be upset and/or irreparable damage may result.
Types
Direct Reading Type
Flat Beam Wrench
- Easy to operate
- When force is applied to the handle, the needle moves to the right or left, indicating the amount of (torque) pressure applied. Once the reading is taken the needle automatically returns to zero.
- Measures in both English or Metric
- Pivoted handle concentrates load at precise point on the lever to assure torque accuracy
- Wrench can be used in both left and right hand directions
- Memory is achieved by fingers that follow the track of the scale and remain in place to indicate the maximum torque applied.
- Meets or exceeds ASME B107.14M and ISO 6789
- Accuracy of all flat beams is +/- 2% of indicated value from 20% to 100% of capacity, in both directions
Dial Wrench
- Named for it's easy to read torque measurement dial, allows the operator to quickly identify the (torque) pressure applied
- Measures torque by way of a needle that moves inside the dial with graduations in both English or Metric
- Wrench can be used in both left and right hand directions
- Memory is achieved by a second needle that indicates the maximum torque applied
- Accuracy of +/- 3% meets or exceeds ASME B107.14M and ISO 6789
Digital Wrench
- Can store multiple torque values in memory
- Torque value remains on display until saved or erased
- High and low percentage tolerances may be pre-set
- Can operate in multiple units of measure
- Wrench can be used in both the left and right hand directions
- Some have data collection capabilities
- +/- 1% accuracy (+/- 2% for Import brand)
Common Uses of Direct Reading Type Torque Tools
- New product design
- Inspection of installed fasteners
- Installation of prevailing torque nuts
Use of Adapters
Use of adapters that change the leverage or length of a torque wrench will alter the tools accuracy. When using Drive Torque Adapters consult Machinery's Handbook to calculate torque offset.
Application Type
Micrometer Adjustable
- The desired torque is determined before the wrench is used, by turning the ring above thehandle to the desired setting on the shaft of the torque wrench
- Once set torque value is achieved a click can be felt and heard
- Remove the set torque by pulling the handle away from the end of the wrench until it clicks
- Scales of measurement available include, foot pounds, inch pounds and Newton Meter
- Most are designed for use in only one direction (either clockwise or counter clockwise).These should not be used to loosen tightened fasteners
- Accuracy of +/- 4%)(+/- 3% for Import brand) meets or exceeds ASME B107.14M and ISO6789
Micrometer Pre-set
- Designed specifically for use on production lines where many fasteners are to be tightened tothe same torque
- Works the same as above but is not adjustable
- A tester must be used to set torque value so most wrenches are drop shipped from the factorywith the users requirements pre-set.
- Accuracy of +/- 4% (+/- 3% for Import brand) meets or exceeds ASME B107.14M and ISO6789
Common Uses of Application Type Torque Tools
- Maintenance
- Installation
- Production
Choosing the Right Tool for the Job
Determine answers to three basic questions:
- Do I need to measure torque (see Direct Reading type) or apply it (see Application type)?
- Do I want the operator to change the settings?
- What are the most common ranges for which the tool will be used?
When Using a Torque Wrench Always:
- Apply load to center of grip
- Avoid use of cheater bars unless supplied by the manufacturer
- Apply load at a constant, steady speed
- Use the wrench in the middle range for accuracy and ergonomic considerations
- Wear safety glasses when using any hand tools
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