For U Solution

When discussing engine maintenance, torque ers to the amount of force required to rotate a bolt around a fixed point or axis. In the United States, the Society of Automotive Engineers (SAE) issues standards for bolt and torque specifications; in most other countries, especially European ones, they use metric equivalents.

Metric Dimensions

In metric units, bolts are listed according to three parameters. The first reading is the major thread diameter, listed in millimeters. The second value represents the distance between the threads, in millimeters. The third value represents the bolts length in millimeters. A metric label for a bolt might look like this: M8-1.25x25.

U.S. Dimensions

U.S., or SAE, bolt dimensions are listed according to three parameters. The first value represents the major thread diameter in inches. The second value is the number of threads in the bolt per inch. The third value indicates the bolts length in inches. An SAE label for a bolt might look like this: 5/16-18 1-1/2.

Pound-Feet vs. Netwon Meters

In U.S. units, torque is generally listed in pound-feet (lb.-ft.) or less commonly in pound-inches (lb-in.). In metric units, the same values are listed in Newton-meters (nm). To convert lb-ft. to nm, multiply the value by 1.356. To convert nm to lb-ft., multiply the value by 0.738. To convert lb-in. to nm, multiply the value by 0.113. To convert nm to lb-in., multiply the value by 8.851.

Nearly every car commercial boasts about the car engines horsepower. But for people outside the U.S., or with a scientific background but not a car background, it may be unclear how much power a horsepower truly is. One horsepower is defined as 33,000 lb*ft/min (pounds times feet divided by minutes). So, converting horsepower into the metric system is simply a matter of converting the separate units of force, distance and time to arrive at a value in Nm/s (Newtons times meters divided by seconds), also known as Watts.

Instructions

1

Convert pounds to Newtons using the conversion factor 4.448 N/lb. If we take the original figure of 33,000 lb*ft/min and multiply by 4.448 N/lb, we get 146,784 N*ft/min.

2

Convert feet to meters using the conversion factor 0.3048 m/ft. If we multiply this by 146,784 N*ft/min (our figure from step 1), we get 44,740 N*m/min.

3

Convert minutes to seconds using the obvious conversion factor 60 s/min. Because minutes is in the denominator of our figure, we must divide the figure by this conversion factor to get the minutes to cancel out. 44,740 N*m/min divided by 60 s/min yields 745.7 N*m/s, or 745.7 W.

4

Calculate the metric power of an engine from its horsepower rating using this figure. Since we know that 1 horsepower = 745.7 W, we can simply multiply the horsepower of an engine by 745.7 to arrive at a value in Watts. For example, a 300 horsepower engine puts out 300 * 745.7 = 223,700 W, or 223.7 kW.

Regardless of the type of bolt, the tightness that a bolt requires -- its torque -- is essential to using a bolt properly. The torque of a bolt will vary depending upon a number of factors, which can make finding torque specs a little difficult. However, there are many ways to find out what the torque specifications are for a particular bolt.

Torque

When speaking of the tightness of a bolt, one is actually referring to the bolts torque. Torque is the amount of force that is required to rotate an object, like a bolt, around a pivot point. With bolts, the torque is the amount of tightening it requires so that the bolt and whatever the bolt is secured to are not damaged.

Metric Bolts vs. SAE Bolts

There are two major categories of bolts: SAE bolts, which are sized by their diameter, pitch thread and length and are measured in inches; and metric bolts, which are sized by their diameter, distance between threads, and length and are measured in millimeters. SAE or American bolts are used in America; metric bolts are used in most other countries. When looking at a bolt torque specification chart, it is important to check the chart for whether the specs are for SAE or metric bolts, since their torque specs will not be the same.

Bolt Grades

Not all bolts are the same. Bolts are made out of different materials that give them different strengths, uses and capabilities. All bolts have a grade, which indicates the strength of a bolt and what material it is made from. Usually the grade is stamped on the head of the bolt, but metric bolts are sometimes unmarked. Higher grade bolts have higher torque values.

Torque Specs

There are many charts available online that will give a rough estimate of a bolts torque specs based on its size and grade; however, all of these charts are approximations. The torque of a bolt will vary depending upon the manufacturer and other factors, such as whether the bolt is lubricated or dry. There are many instances in which knowing exact bolt specs is essential; for instance, preventing a bolt from breaking or a material from warping. In these cases, contacting the supplier of the bolts for their specs or looking for a chart that is specifically designed for a certain brand of bolt is very important.