Gear Wrench Electronic Torque Wrenches
by Hib Halverson
This is our first experience with “electronic torque wrenches”. Admittedly, that’s a bit odd considering the amount of coverage the V-Net’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, brake caliper bracket bolts and other critical fasteners, the go-to tool in our shop was a dial-type torque wrench which has been in 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 one of each (⅜-drive PN 85076, ½-drive PN 85077).
The GrearWrench ⅜-drive Electronic Torque Wrench’s measurement range is 7.4-99.6-ft/lbs (10-135-Nm) and the ½-drive unit’s measurement range is 25-250 foot-pounds (34-340 Newton-meters). Both are accurate to ±2%, clockwise and ±3%, counterclockwise from 20% to 100% of their scale. Both come in blow-molded cases with instructions and an accuracy certificate. Each is covered under a limited one-year warranty. Additionally, GearWrench ETW calibrations are warranted for 90-days.
That ½-drive tool goes to 250-ft/lb. is why it has such a long handle. It’s length makes tightening fasteners which need 140-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 in which you could go past the intended torque with very little effort. There is a solution. Try the smaller GearWrench ETW because the ⅜-drive tool is much easier to use when the require tightness is less than, say–40-ft/lbs.
How does an 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 strain 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.
The first time we used one of these ETWs, it didn’t work. Figuring 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. Silly us…they’re inside the end of the handle. We unscrewed the cap and, viola! No batteries.
Once we dropped in a pair of AAs, 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 140-ft/lbs then used it to tighten a new set of McGard Wheel Locks we added to the V-Net’s ATS-V Coupe.
We tightened the five nuts in three passes using a star pattern and, on the final pass, when we hit 140, heck–the ETW vibrated. Imagine our surprise. This use of haptic technology is pretty neat.
On today’s engines, such as the 3.0 and 3.6-liter “High-Feature V6” engines used in many Cadillacs such as the ATS-V and CTS-V-Sport there are a lot of fasteners for which using a 1/2-drive torque wrench is not be a good choice. For example, say you are replacing an LF4 engine’s oil pressure sensor. To safely tighten that, you need a shorter torque wrench and that’s were the GearWrench ⅜-drive ETW comes in. The torque spec. for that sensor is 15-ft/lbs. Not so easy with the big ½-drive ETW but the ⅜ unit is perfect for that. When you near 15-ft/lbs then hit the number, you get the same aural and haptic warnings.
Handle vibration is just part of a clever system of advising the user when he/she is reaching the desired torque level. Simply signaling 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 ½-drive ETW’s length, which makes torques in the 150- to 250-ft/lb. range easier to attain and we like the feel the handles on both tools
GearWrench’s Electronic Torques are a welcome addition to our tool box. We’re going to put our trusty old 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.