5-101.bk Page 21 Friday, March 17, 2006 11:05 AM Inch Thread vs. Metric Thread Fastener Combinations Contributing to Assembly Weakness Incompatible Metric vs. Metric Fastener Systems Thread mismatch can also result when combining fasteners from incompatible metric fastener systems. The resulting faulty thread engagement typically causes thread stripping and/or assembly weakness which may lead to service failure. The following inch/metric screw and nut (or tapped hole) combinations can be fully tightened, but the resulting assembly will be 25% to 60% weaker than required. Service failure of the assembly is probable.
CONVERSION FACTORS Inch Screws Metric Nuts 1 inch = 25.4 millimeters *4-48 M3 x 0.5 1 mile = 1.61 kilometers 5-40 M3.5 x 0.6 1 pint (U.S. liquid) = .473 liter *8-36 M4 x 0.7 6-40 M3.5 x 0.6 1 quart (U.S. liquid) = .946 liter *10-32 M5 x 0.8 1 pound-foot = 1.3558 Newton-meters 1 cubic inch = .01639 liter 12-24 M6 x 1.0 1 horsepower = .746 kilowatt *1/4-28 M7 x 1.0 1 pound/square inch = 6.895 kilopascals 3/8-16 M10 x 1.5 1 pound/square inch = 27.6 inches of water/2.04 inches of mercury 7/16-14 M12 x 1.75 1/2-13 M14 x 2 degrees Fahrenheit = (1.8 x degrees Celsius) + 32 3/4-10 M20 x 2.5 1 gallon (U.S.
liquid) = .83267 imperial gallon *3/4-16 *M20 x 1.5 1 millimeter = .03937 inch 7/8-9 M24 x 3 1 kilometer = .6214 mile *Fine thread 1 liter = 2.1134 pints (U.S. liquid) 1 liter = 1.0567 quarts (U.S. liquid) Inch Nuts Metric Screws 1 liter = 61.024 cubic inches *5-44 M3 x 0.5 1 Newton-meter = .7376 pound-foot *6-40 M3.5 x 0.6 1 kilowatt = 1.34 horsepower 8-32 M4 x 0.7 1 kilopascal = .145 pound/square inch *8-36 M4 x 0.7 1 imperial gallon = 1.2009 gallons (U.S. liquid) degrees Celsius = .556 x (degrees Fahrenheit – 32) *10-32 M5 x 0.8 12-24 M5 x 0.8 000068a *12-28 M5 x 0.8 *1/2-20 *M12 x 1.25 3/4-10 M18 x 2.5 *3/4-16 *M18 x 1.5 *1-12 M24 x 2 1-8 M24 x 3 *Fine thread Page 2-21 200 SPECIFICATIONS