What is your immediate thought when you see 1/2 - 13 X 5? Some may see an equation that needs solving while others may be confused with this all together. Do not fret, you are not alone in this confusion, but we aim to fix that!
What you see is the proper dimensioning scheme for a bolt or screw. This is how the diameter (1/2), thread pitch (13), and length (5) are correctly identified.
A good general rule is that any number or fraction is followed by a dash and another number refers to a diameter - thread pitch. In this example: 1/2-13 the diameter is 1/2 followed by a thread pitch of 13.
The second aspect of this dimensioning scheme is length. When a number follows an "X" this is referring to the length of the fastener. In this example 1/2-13 X 5 - the X 5 is referencing the length of 5".
Below, you can find additional information regarding the diameter, thread pitch, and length of screws or bolts, what they mean, and how each of these dimensions are measured. Please look at our blog Fastener Facts: Tips & Tricks for more help with defining your fastener!
Diameter – The diameter of a screw or bolt refers to the measurement of the distance across the outer surface of the threaded section. In the case of a screw, this is the distance across the threaded portion, while for a bolt, it is the diameter of the shank (non-threaded portion) since the threads are typically excluded from the measurement. For additional information please see our blog What to Know About the Threads of a Fastener.
Thread Pitch – This is the measurement of the distance between adjacent threads of a fastener. When using Standard also known as Unified Thread Standard (UTS) this is measured by the amount of complete thread revolutions per one inch, referred to as TPI. On the other hand, for a metric fastener, this measures how many millimeters separate adjacent threads at their peaks. For additional information please see our blog What to Know About the Threads of a Fastener.
Length – A good general rule is that the length of a screw or bolt is measured from where the screw would sit flush to the mating surface after installation. For additional information please see our blog on How to Measure the Length of a Screw or Bolt.
Now Let's Get Building! ®