Let’s say that you want to torque a bolt to 40 ft-lbs, but you’re using a 2-inch-long wrench extension. For the sake of example, the length of the torque wrench is 14 inches (from center of the handle to center of the drive). Adding the 2-inch wrench extension makes the total length (center of grip to bolt-engaging wrench) 16 inches. In this case, you divide the length of the torque wrench (L, from the center of the handle to the center of the drive) by L+E, then multiply that ratio by the desired value.
In this example, the formula works out to: 14 ÷ 16 × 40 = .875 × 40 = 35.
In this example, where you want to tighten at 40 ft-lbs, using a 2-inch extension, you set the torque wrench at 35 ft-lbs.
It’s important to orient the wrench extension in-line with the torque wrench itself, to achieve a straight shot from the torque wrench body to the extension. If you angle the extension off-parallel to the torque wrench, this inaccurately affects the applied torque.
If, due to required access of the bolt, the wrench extension needs to be placed 180 degrees (still in line with the torque wrench but effectively making the total wrench reach shorter), and you still want to achieve 40 ft-lbs of torque, you need to compensate for this shorter distance my modifying the formula as TW = L ÷ L - E, × DESIRED TE.
If the torque wrench length (center of grip to center of head) is 14 inches, and the wrench extension is 2 inches long, with the extension effectively reducing grip-to-bolt engagement distance, and you still want to achieve 40 ft-lbs of torque, the new formula is as follows:
For areas that are difficult to reach that prevent you from using only a socket on the torque wrench, an offset wrench extension may be used. When using an extension that effectively increases the length of the torque wrench, you must adjust the applied torque to compensate. Otherwise you overtighten beyond the desired torque value. The length of the extension must be factored to properly adjust your torque. A wrench extension is marked for its length.
When using a wrench extension on your torque wrench, always keep the extension parallel to the torque wrench body. If it is not parallel/straight, it results in an inaccurately applied torque.
14 ÷ 14 - 2 × 40 = 46.6
Because the leverage of the setup has decreased, to achieve 40 ft-lbs, you adjust the torque wrench at 46.6 ft-lbs.
• If the adapter makes the wrench longer, you must back off on the torque wrench setting.
• If the adapter makes the wrench shorter, you must increase the adjustment on the torque wrench.
Special Torque/Angle Torque Wrenches
Thanks to advancements in technology, torque wrenches are now available that allow you to achieve both torque value and applied rotation angle without the need for a separate angle gauge.
One example is Snap-on’s Techangle series of wrenches. Featuring sensor electronics and digital control and readout, you can preset (program) the torque value you want; or both torque value and final applied angle, depending on your needs. The electronic control allows you to also choose between in-lb, ft-lb, or Nm, plus angle.
An internal gyroscope provides the desired angle sensing.
Here’s how it works: you program the desired torque value, and tighten the fastener. When you reach the programmed torque value, the wrench beeps and vibrates.
Then, if you need additional angle rotation, you program the desired angle.
When you continue to apply pressure and reach the programmed angle, the wrench again beeps and vibrates.
The preset angle range is 5 to 360 degrees, with a resolution of 1 degree and accuracy of +/- 1 degree. Unlike the use of a separate angle gauge, where you can’t ratchet (with an angle gauge you must start and continue the angle rotation in a steady, one-direction sweep), this tool allows you to ratchet without “losing” the angle memory. Pretty cool.
Two models are currently available, including ATECH2FR100, with a torque range of 5 to 100 ft-lbs; and ATECH3FR250, with a torque range of 12.5 to 250 ft-lbs.
Prior to the installation of lifters and pushrods, a camshaft lobe gauge can be used to accurately determine the position of an individual camshaft lobe (for instance, when positioning a cam with a specific intake or exhaust lobe at its base circle, or determining a lobe at its peak, or measuring a lobe from base circle to peak to verify the lobes against published lift specs). This tool features an aluminum tubular body with an adjustable plastic section that expands to lock the body into the lifter bore (adjustable for various lifter bore diameters). At the lower tip is a spring loaded, rounded plastic plunger that contacts the cam lobe. At the top is a gauge. Rotate the camshaft until the lowest reading is obtained (with the cam lobe on its base circle). Zero the gauge needle. As you rotate the camshaft, the gauge shows the lobe ramp and maxes out at peak lift. For instance, if the camshaft lift (not valve lift) is specified at .500 inch, when the lobe has reached maximum lift, the gauge shows the existing amount of lift. You then compare this to published lobe lift. This is a very easy tool to use and offers several applications when you need to monitor the position or base-to-peak travel.
The indicator is zeroed after the camshaft is rotated so that the gauge plunger contacts the camshaft base circle. This gauge allows you to not only locate the base circle, but to measure the cam lobe ramp and peak as the camshaft is rotated. A camshaft lobe checker gauge features an aluminum body, a dial indicator, and a spring-loaded plunger. The plunger is a plastic composite material, placed directly onto a camshaft lobe. The gauge body features an expandable collar that allows you to rotate the body to lock the tool into the lifter bore.
Conversions
Metric
1 Newton Meter = .741 ft-lb
1 Newton Meter = 8.892 in-lb
1 mKg = 7.25 ft-lb
1 cmKg = .870 in-lb
1 nKg = 9.8 Newton Meter
1 Meter = 100 centimeters
1 Meter = 39.37 inches
1 Meter = 3.2808 feet
1 Kilogram = 1,000 grams
1 Kilogram = 2.2046 pounds
1 Newton = .2258 pounds
English
1 in-lb =1.15 cm.Kg
1 ft-lb = 1.35 Newton Meter
1 in-oz = 28.35 in. gram
1 in-lb = 16 in-oz
1 ft-lb = 12 in-lb
1 foot = 12 inches
1 pound = 16 ounces
1 pound = 453.59 grams