Gear Wrench ½-inch Drive Electronic Torque Wrench
by Hib Halverson
This is our first experience with an "electronic torque wrench". Admittedly, that's a bit odd considering the amount of coverage the CAC's product evaluation staff has given technology in tools such as scan testers, wideband oxygen sensors, tuning software and the like.
Up to now, when we needed to torque wheel nuts, head bolts, brake caliper bracket bolts and other critical fasteners, the go-to tool in our shop was a Snap-On dial-indicator torque wrench which has been on our tool box for longer than we care to admit.
Obviously, we were overdue to try an "ETW" so, when we saw GearWrench's new ⅜-inch and ½- inch drive Electronic Torque Wrenches at the 2015 SEMA Show, we took the plunge and ordered the ½-drive version (PN 85077) as that is the drive size we use most when we need a torque wrench.
The GearWrench ½-drive Electronic Torque Wrench's measurement range is 25-250 foot-pounds (34-340 Newton-meters). Its accuracy is ±2% for clockwise tightening from 20% to 100% of their scale. It comes in a blow-molded case. It is covered under a limited one-year warranty. Additionally, the ETW's calibration is warranted for 90-days.
That this wrench goes to 250-ft/lb. is why it has such a long handle. It's length makes tightening fasteners which need 150-lbs/ft and above, easier. Conversely, the length of the tool might make using it a little difficult on fasteners which torque to 25-50-ft/lb. because of the ease of which you could go past the intended torque with very little effort. Gear Wrench has a solution for that: the "target torque alert". More on that in a bit.
How does the Gear Wrench Electronic Torque Wrench Work? Its key component is a "strain gauge", a strip of conductive metal that has a voltage applied such that current flows though it longitudinally. The strain gauge is connected to the head of the wrench which deforms slightly when torque is applied. That small deformity is transferred to the stain gauge and when it stretches, its electrical resistance increases.
From change in resistance, the ETW computes the amount of torque per unit that was applied to the wrench head. That data goes to a transducer which converts it to a small current. The ETW uses that current to drive the LCD display screen and to enable the red LED, the tone generator and a haptic warning generator in the handle.
At first, the ETW didn't work. Figuring this was a battery issue, we looked over the tool and could not see a battery compartment. When in doubt, RFM. The last paragraphs on the backside of the instruction sheet covers batteries. They're inside the end of the handle. We unscrewed the cap and, viola! No batteries. Unbeknownst to users who don't read the manual first, GearWrench ETWs ship with no batteries.
Once we put a pair of AAs inside the handle, we powered-up the tool. Using the "units" key, we set the wrench to read in foot-pounds but it can also be set to read in inch-pounds and newton-meters. With the arrow keys and the "set" button, we programmed the Electronic Torque Wrench for 100-ft/lbs then used it to tighten a set of Katech's titanium lug nuts we added to the "Blue Bullet 2", the CAC's 2012 Z06 test car.
We tightened the five nuts in three passes using a star pattern and, on the final pass, when we hit 100-lbs/ft., heck–the ETW vibrated. Imagine our surprise. This use of haptic technology is pretty neat. In fact handle vibration is just part of a clever system of advising the user when he/she is reaching the desired torque level.
Simply advising the user that the desired tightness has been reached can result in the torque target being exceeded, so it's also good to let the user know when the desired torque is being approached. The Gear Wrench Electronic Torque Wrench does both. Its programming was written such that not only can the tool be configured to alert the user that the fastener's desired torque number has been reached, but it can, also, be set for a "target torque alert" which warns that fastener tightness is approaching the desired torque.
The target torque alert is set by pushing the "%" key, using the arrow keys to select the tolerance, then saving the entry by pushing the "%" key a second time. Ten percent below the desired torque is common value to set for the torque alert.
Once you have the alert set, as fastener torque gets within 10% of the target, the tool makes a pulsing tone. When the desired torque is reached, not only is it shown on the tool's display, but a red LED comes on, the tone sounds continuously and the handle vibrates.
We like the intuitive way the GearWrench Electronic Torque Wrench advised the user of both approach and arrival at the desired torque. We like the ETW's length, which makes torques in the 150- to 250-ft/lb. range easier to attain and we like the handle's feel.
GearWrench's Electronic Torque is a welcome addition to our tool box. We're going to put our trusty old Snap-On dial indicating torque wrench on eBay. Maybe someone who buys antique tools will take an interest.
For more information on these ETWs, visit GearWrench's web site.