Whenever the 1920s are discussed in documentaries, they are first referred to as roaring and then as depressing. Too often, too little attention is paid to what happened in between these two extremes.
One key event was increased consumer demand for many products, especially automobiles. This, in turn, led automakers to invest in more machinery and tools—including making their own when needed.
“In 1924, Chrysler Corp. founder Walter P. Chrysler noticed that cylinder heads on the company’s aluminum engine blocks were being unevenly torqued,” explains Ryan Sarti, marketing director at Sturtevant Richmont. “Since there was no standard to determine how tight is tight, Chrysler invented the first deflecting beam torque wrench. This enabled engine heads to be tightened in a repeatable fashion.”
That same year, Chrysler licensed Paul Sturtevant to manufacture and sell the beam torque wrench; in essence, beginning the concept of error-proofing the fastening process. Sturtevant eventually patented the torque wrench in 1938.
Eighty-plus years later, Sturtevant Richmont still makes beam torque wrenches, as well as several other types. Its customers include manufacturers in every industry.
For the last two years, an electrical manufacturer has used Sturtevant Richmont’s 1250 Series Exacta click torque wrenches, in conjunction with its Global 400 controller, to ensure the torque accuracy of each fastener on a popular industrial product. The wrenches are radio embedded and measure both torque and angle of rotation in different combinations to provide full control over the final fastening outcome.
Prior to this, the manufacturer had one assembler tighten each fastener and check it with a standard click torque wrench from a different supplier. Another assembler would recheck each fastener with the same type of torque wrench and mark each fastener that meets torque specification. Finally, an inspector would check that all fasteners had the appropriate mark on them.
The problem, according to John Reynertson, president of Sturtevant Richmont, was that quality engineers at the manufacturer heard noise whenever they shook a box containing an assembled product. This indicated loose components and resulted in excessive warranty work by the manufacturer.
The benefit of using the torque controller, notes Reynertson, is it only recognizes work done with a paired wrench that is preset to an active parameter; in this case, a batch count. When the wrench verifies that the torque is compliant on a fastener, the batch count advances.
“Switching to our wrenches and controllers has virtually eliminated the warranty work,” says Reynertson. “It has also greatly improved profitability because the manufacturer is able to employ everyone in production, without having them check and mark work that was already done. More importantly, their reputation among end-users improved because they are no longer shipping defective products.”
Manual torque wrenches, as well as torque screwdrivers, are accurate, durable and low cost. These benefits not only make them effective to use in fastening nuts and bolts in production and auditing applications, but also as a complement to pneumatic and electric tools on the assembly line. Having power and manual tools available ensures that the line will continue to function without a costly shutdown.
A Positively Wrenching Experience
Several types of manual torque wrenches are offered by suppliers. These wrenches usually have the appearance of a socket wrench, but vary somewhat in internal mechanisms and recommended application.
The deflecting beam wrench is the simplest. In this design, a beam connects the head of the tool with the handle. A pointer is connected to the head, parallel with the beam. The pointer extends almost to the handle, but does not connect to it. At the base of the handle is a metal plate with a torque scale.
When the wrench is pulled, the beam deflects, but the pointer stays still, indicating the torque on the scale. This design is accurate and durable, but reading the scale can be difficult.
In 1948, the Australian company Warren and Brown developed the dual-signal deflecting beam torque wrench. This tool applies torque to deflecting beams, instead of standard coil springs, and it uses a dual-signal trip mechanism to read torque.
This design is said to make the wrench more accurate and provide more consistent readings than the standard deflecting beam type. End-users especially like that the wrench provides audio and visual feedback when the required torque is obtained.
Dial wrenches are easier to read. In this design, a torsion bar goes from the head of the tool to a rack-and-pinion mechanism. As the bar deflects, the mechanism turns a dial that indicates torque.
Click torque wrenches are the most common type used on assembly lines. This is because operators don’t have to read a dial or gauge; they simply pull the wrench until it clicks. In this design, the drive head is connected to a lever that, in turn, is connected to a toggle mechanism and an adjustable compression spring.
As a load is applied to the handle of the tool, the lever shifts the toggle, compressing the spring. When enough load is applied, the spring triggers the toggle with an audible click, and the tool becomes rigid.
A cam-over, or slipper, torque wrench consists of a roller and cam (or similar) mechanism. The roller pushes against the cam, which is attached to the driving head. Pressure from the roller locks the cam in place with a specific force that is provided by an adjustable spring.
If the required torque is greater than the holding force of the roller and spring, the wrench will slip and no torque will be applied to the bolt. This type of wrench will not overtighten the fastener should the assembler continue to apply torque beyond a predetermined limit.
“The easiest way to understand torque wrenches is to categorize them as being either indicating or signaling,” notes Reynertson. “Standard beam and dial type wrenches indicate torque, whereas the click and cam-over wrenches provide a clearly audible sound, or signal. A click wrench sounds when the preset torque is reached; a cam-over when the maximum torque is reached.”
Although manual wrenches are simpler than electronic wrenches, they increasingly incorporate high-tech features. For example, many models that used a dial to measure applied torque now provide a digital readout for easier reading by the assembler.
Some click wrenches now have electronic sensors that detect the release of the toggle mechanism. The sensor communicates each click of the tool to a PLC through a cable or a wireless connection.
This feature enables engineers to error-proof the process. Consider an application where the operator is supposed to check four bolts on an assembly. If the PLC only records three clicks of the wrench, the assembly cannot be released to the next station.
Tohnichi America makes the CSPFHW series of wrenches, which are radio-frequency models with double tightening detection. Andrew Kuby, product support specialist at Tohnichi, says that the wrenches feature a built-in gyroscope that can detect a double tightening operation.
The wrenches can be set from 5 newton-meters to 280 newton-meters, and they confirm the required torque set has been achieved by sending a confirmation signal to a receiver box. The tool also counts and tracks the number of fasteners that have been tightened via a PLC or the company’s CNA-4mk3 count checker.
“Manufacturers have realistic but high expectations of today’s torque wrenches,” says Jeff Hayden, national sales manager at Crane Electronics Inc. “They want accurate tools that provide reliable power and data, while at the same time eliminating the inconsistent performance of the operator. In addition, they want tools that make the most of wireless, radio frequency and Bluetooth technologies.”
The IQWrench2 from Crane is a manually pulled, electronic transducerized beam wrench that combines high accuracy with a torque data collection system. It incorporates a vibrating handle and radio-frequency data transfer with optional bar code scanning capability. Plus, its advanced software can be upgraded at any time, increasing flexibility.
Hayden says that the tool comes with a wide selection of quick-release interchangeable heads (SR, fixed, Din), which have automatic digital identification and adjustable torque settings. The tool has a torque range of 0.5 to 1,500 newton-meters and is durable enough for harsh production environments.
“The algorithms in this wrench are able to detect and tell the operator when the fastener moves, and where it turned or relaxed,” explains Hayden. “Digital and smart, the wrench time-date stamps all data, and uses red, yellow and green lights to indicate high, low and good torque.”
Desoutter Industrial Tools’ Delta manual torque wrench comes in three versions, all of which feature a double-bridge transducer and can measure torque and angle in production and quality applications. The standard unit has a visual backlight RGB color display and a complementary vibrating sensation system for optimal operator guidance. Interchangeable heads and reversible ratchets are standard.
Six models make up the WLAN series, with the smallest model having a torque range of 3 to 30 newton-meters, and the largest at 80 to 800 newton-meters. These tools feature a bidirectional communication protocol (DeltaWrench WLAN) that easily interfaces to custom applications via communication bridge software.
The third type is the Zigbee, which allows the operator to pair the wrench to the company’s E-LIT Box on a touch screen but without a PC. Torque range is the same as the WLAN.
“It’s an interesting situation regarding current end-users of manual torque wrenches,” notes Russ Hughes, product marketing manager at Desoutter. “The tools have progressed to become the smartest they’ve ever been. Many even allow for wireless collection and downloading of data from the server. At the same time, some manufacturers prefer having a basic tool with a nice display of torque data that they can manually write down.”
Equally important and beneficial to assemblers is the availability of tools that allow for the easy interchange of wrench heads, especially smart ones. Hughes says that such heads ensure that the assembler can never apply the wrong level of torque to a fastener.
TB manual wrenches from Mountz Inc. feature a fixed head that breaks-over when preset torque is reached to eliminate overtorquing. Six models are available, each with a different aluminum handle color (black, blue, red, green, yellow or white). The series has a torque range from 25 inch-ounces to 50 inch-pounds. Torque is adjusted by removing the end cap and turning the adjustment screw with a 0.1875-inch hex key. It is then verified by using a torque analyzer.
Driven to Accuracy
Manual torque screwdrivers are another important tool that assemblers rely on to ensure proper torque. The first such screwdriver was patented by Frank Livermont in 1961 and featured a limited-slip clutch. Most of today’s torque screwdrivers feature a torque-limiting clutch that disengages once the proper torque has been reached. Low-, mid- and high-torque range screwdrivers are available.
“Some common examples of manual torque screwdrivers are cam-over, limited-slip, dial-indicating and digital,” says Kuby. “Dial-indicating screwdrivers are primarily for inspection and auditing purposes. Digital models are used for data collection, which is increasing in importance.”
Preset and adjustable torque screwdrivers are also available, according to Dave Cash, a technical application specialist at Mountz. The former is preset to the required torque value for the application and then signals the operator when the torque is reached. This tool has an internal adjustment mechanism for setting torque value, and it must be preset using a torque tester.
Preset screwdrivers are typically used in production applications where there is one torque setting required and the manufacturer needs to prevent incidental or operator tampering of the torque setting. However, if the torque specification changes or a new project requires a different torque setting, the preset torque screwdriver is still flexible enough that a new torque can be set internally using a torque analyzer.
Adjustable torque screwdrivers offer different setting options for applications that require more than one torque value. It features an external adjustment scale, as well as a ring or bezel device. The operator presses down the device to adjust the torque setting and lock it into place to prevent incidental torque adjustment. These tools are ideal for field service or production applications due to their flexibility.
Sarti points out that applied thrust force can change the output of a torque screwdriver. The tool may have one reading in the calibration lab and appear to be within tolerance. Out in the production area, however, the tool’s applied force reading may be quite different.
This past August, Mountz introduced its FG preset hand screwdrivers that offer accuracy, repeatability, precision, durability and a calibration life of more than 20,000 cycles. Service is not required until more than 100,000 cycles.
One key feature is advanced cam-over technology that provides a completely smooth reset, reducing the risk of loosening or breaking fasteners. In addition, a patented secure bit-locking mechanism with one-touch release can only be activated by the user for applications that require greater flexibility and efficiency on the line. This design also prevents the operator from incidentally applying axial load on the fastener.
“You can give this to tool operators of all skill levels and feel confident that the correct torque is being applied,” says Brad Mountz, CEO of Mountz. “The chances for errors and breakage are greatly reduced. These preset drivers are designed to improve overall product quality, and worker productivity and safety in precision industrial applications.”
The FG line has a torque range from 0.8 up to 125 inch-pounds. Plus, the tools exceed the accuracy and repeatability requirements of ISO6789: 2017.
According to Mountz, the sleek tool feels great in the operator’s hand because the handle has few flutes and large recesses. He says that this design makes them more comfortable to hold, less likely to cause hand fatigue and easier to clean.
The tools are backed by a two-year unconditional manufacturer’s warranty. They also have a lifetime guarantee against manufacturing defects, and the initial recalibration in the first year is included.
“We don’t care if you run it over with a forklift,” says Mountz. “If it breaks, we’ll fix it or replace it for free.”
Preset RNTDLS screwdrivers by Tohnichi are error-proofing tools that feature a relay signal cable to confirm and count each tightening click on a fastener. The driver’s toggle is activated when the set torque is achieved. Rotary slip occurs simultaneously with output of a contact signal from the limit switch.
According to Kuby, these tools do require torque to be set with a tester and key, so that torque is set to one value and secured from unauthorized changes. Wired and wireless versions are available.
Sturtevant Richmont’s SR PM series of preset torque screwdrivers are ideal for any application requiring high repeatability at low torque. The screwdrivers use standard 0.25-inch bits, adapters and sockets, and have a bidirectional accuracy of ±6 percent of the preset value.
“The operator cannot over-torque the screw because the clutch automatically releases when the desired torque has been achieved,” says Sarti. “Also, the tool can be set in any unit of torque measurement, and its short dwell time prevents repetitive motion injuries.”
Desoutter has offered torque screwdrivers since 2003. Its popular TS dial-indication series can be operated in either normal or memory mode. The four models in the series have a torque range of 50 to 500 centinewton-meters.
Hughes says that regular users of Desoutter manual torque screwdrivers include Bose, in its engineering test labs; Raytheon, for missiles; Harman Becker Automotive Systems, on JBL electronic products; and Keurig, for low-torque screws in coffee makers.