How to Read Metric Tools

Mechanics depend on metric tools to repair foreign-made automobiles. Traditional American tools, often called standard or SAE tools, were developed according to size standards set by the Society of Automotive Engineers, with measurements given in fractions of an inch. Other countries adopted metric standards established through the System of Units, or SI, which is maintained by the International Bureau of Weights and Measures located in Paris, France. A good mechanic must be able to use both systems.

Instructions

1

To read metric measurement tools, look for the imprinted, engraved or raised lettering on the tool. For wrenches, look on the handle's flat side. For sockets, look for engraved markings in the outer side. You will see a number often followed by lettering. First determine what letters you see. The small letter "m" stands for meter, which is the unit upon which all other units of measurement are based. A meter is equal to 39.37 inches. Interpret "mm" as millimeter, which is 1,000 times smaller than a meter or .03937 inch. Read "cm" as centimeters, which is 10 times larger than a millimeter or 10 times smaller than a meter.

2

Read the number that comes just before the lettering, which will tell you the precise size of the tool. For example, a socket marked "10mm" is read as 10 millimeters. For sockets and wrenches simply marked with a number and no letter, read the size as though the "mm" lettering was included.

3

Read a metric measuring tape or ruler by first reading the unit of measurement it uses. Usually each small marking is a millimeter, and the tool will carry the marking "MM" at one end. The numbers are in centimeters, or 10 millimeters. So you read a measurement of 3 with two small marks after it as either 3.2 centimeters or 32 millimeters.

4

Read each increment as 1/10 of the unit of measurement when using gauges. Those made for making minute measurements may use micrometers, each micrometer being 1/1000 of a millimeter, or 0.001 mm. The symbol for micrometer is m.

5

To read liquid measurement tools, such as battery fillers, look for the letter "L," which stands for liters. A liter is the metric unit upon which other measurements of capacity are made and is equal to 1.056 United States liquid quarts. If you see lettering that reads "mL," the numbers before the lettering will give you the capacity or quantity in milliliters, which are 1/1000 of a liter.

6

Read the electrical rating of tools by looking for W, which stands for watts; V, which is volts; J, which is joules, a measurement of energy, work, or quantity of heat; A, which is amps; and Hz, which reads as hertz, which is frequency. You can read the amps for which your power tool is rated, multiply by the voltage it requires, and learn how many watts per hour is expended by use of the tool.