Be careful with metric HT bolts and allen bolts (socket head cap screws).
What you get most of the time is not what you expect.
Use genuine 'UNBRAKO' socket head cap screws and specify 12.9
available from Blackwoods
http://www2.blackwoods.com.au/infoBANKProduct.aspx?SG=2000165&S=16&G=2003612&P=7119988
Check SPS Technology for tension
Below is from SPS Technology who make Unbrako
[FONT=TimesNewRoman,Bold]International and foreign standards for metric sizes[/FONT]
The International Standards Organization's ISO 898 contains a system of "property
classes" that perform a function similar to the SAE J429 grade designations. These
property classes differ in material - and have up to a 100 percent difference in strength.
The two most pertinent property classes are 10.9 and 12.9.
The numerals used in property class designations refer to the nominal ultimate tensile
strength and nominal percent yield strength. For example, a Property Class 10.9 fastener
has a 1,000 MPa nominal ultimate strength and a yield of 90 percent of ultimate. The
strength of Property Class 10.9 allows the use of plain carbon steels while Grade 8 calls
for only alloy steels.
The U.S. industry standards for metric, alloy steel socket head cap screws, ASTM
A574M, specifies one strength level. This strength level is equivalent to ISO 898
Property Class 12.9 and is similar to the strength level for inch socket heads. Although
the U.S. standard specifies only one strength level, metric socket screws are
manufactured around the world to various standards. These standards allow strength
levels and materials different from the U.S. standard. Property Class 6.8 has a nominal
tensile strength (600 MPa) only one half of Property Class 12.9 (1,200 MPa). Therefore,
there are metric socket screws in distribution that look similar but have different
strengths.
Metric socket head cap screws used in the United States are normally the 1,200-MPatype.
However, recent activities of international standards committees have resulted in
the acceptance of the 10.9 Property Class as a standard for socket heads. Pressure for this
came mostly from the continental European delegations. This property class has lower
strength than U.S.-accepted standard and may even be a different material class. The
acceptance of the 10.9 Property Class means there will be a greater influx of Property
Class 10.9 products in distribution, increasing the potential in the United States for
inadvertent substitution.
