All bolts whether standard or metric are sized according to diameter thread pitch and length. An m12 15 x 50 metric bolt is 12 mm in diameter has a thread pitch of 15 mm and is 25 mm long.
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How to read bolt sizes. Determine the length of the metric bolt by looking at the third number. Read the second number. How to read screw sizes. Each part including the thread pitch is a measurement in millimeters so each may be followed by the abbreviation mm. To determine the size of a bolt first measure the diameter. It seemed to fit the best with the 10 32 model but 8 32 was pretty darn close as well.
In the unified thread standard uts system manufacturers list the diameter size as a number between 0 and 10 with 0 being the smallest and 10 being the largest. This the largest diameter. For example a standard 12 162 bolt is 12 inch in diameter has 16 threads per inch and is 2 inches long. Often this is left off from the thread pitch. Unified screw diameters are. There is an exception thoughif pitch isnt specified the fastener is coarse threaded.
Diameter is in either inchesnot decimal or millimeter. Measure in inches from the tip to where the screw head rests to get the length. This is either the number of threads per unit of the distance between threads. The first number shows you the major diameter or the diameter of the grooves on the screw shaft. Use the first number to figure out the diameter of the threads. Look on the bolt head for the number denoting the strength of the bolt.
The shank is the shaft like part of the bolt. The measurement of the screw on the thread. Second measure the pitch pitch is threads per unit. Read the first letter of the size. The bigger the number the stronger the bolt. The size of a metric screw or bolt is specified as diameter pitch and length in millimeters millimeters is abbreviated mm.
For example if the metric bolt was m14x15x25 it would have a length of 25 millimeters. Use a ruler or measuring tape to measure from here to the tip of the screw. At that point it would probably be best to get the bolt in both sizes and try them out. For nuts size will appear as diameter and pitch. In metric fasteners an x is used to seperate each of the parts of the size. Sometimes it is also left off of the other parts of the size.
Title image from basil arteomovflickr. Wherever the screw head would rest when it is fully embedded in something is where you start the measurement. How to measure bolt size step 1 measure the diameter of the shank. Also known as the. For example i overlaid a bolt onto the print out chart to see if i could figure out what size it was.
Gallery of How To Read Bolt Sizes
