Solutions for Static Bolted Connections

Property Classes & Codes

A quick insight into the various strength designations (for example 8.8 or 12.9) for steel bolts, threaded rods etc has some useful information embedded in it.
The code is made up of two digits separated by a dot/point. This is just a way of separating the two parts of the code. The number to the left when multiplied by 100 gives you a good estimate of the Tensile Strength of the fastener's base metal in MPa (Mega Pascals), while the number to the right when multiplied by 10 times the first/left hand/preceding number gives the Yield Strength also in MPa.

Worked Example

Let's apply the two formulae to the 8.8 designation, so that we can quickly derive a good working estimate for the Tensile and Yield Strengths.

Tensile Strength estimate takes the left hand / first digit and multiplies this by 100.
which is 8 x 100 = 800 MPa,
and the Yield Strength takes the left hand number multiplies it by the righthand / second number and that product by 10
which is 8 x 8 x 10 = 640 MPa
Likewise 12.9 tells us that the Tensile Strength is 12 x 100 = 1200 MPa, and the Yield Strength is 12 x 9 x 10 = 1080 MPa.

Nuts and Proof Load stressYield Strengths

You will have noticed that nuts only have a single digit? Well this is useful too. This single digit code gives us the Proof Load Stress (also in MPa). We derive this from the left hand digit of the Property Class Code / Grade of the bolt, which when multiplied by 100 for an 8 gives us the Proof Load Stress for the Nut of 8 x 100 = 800 MPa.

Solutions for Static Bolted Connections

This is a summary of the key technical data for the fasteners associated with static Bolted Connections that we manufacture, for additional information, please do not hesitate to ask.