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Gade 8 bolts

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Be careful with Grade 8 bolts, if they have a gold color they might be cadmium coated, others may be zinc coated. Several years ago there were a multitude of "counterfit grade 8 bolts on the market" They were sold as grade 8 but did not meet the specs. The Tank Truck Magazine "Modern Bulk Transporter" ran an article on them identifying all the different counterfit bolts by their manufacture and markings about 1992 or so.


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The starting material for SAE J429 Grade 8 Bolts is usually AISI C4140 or C4150 hence .40% or .45% Carbon. Grade 8 bolts are identified by 6 radial lines on the bolt head.

Grade 5 Bolts usually start as AISI C1045 or .45% Carbon. Grade 5 bolts are identified by 3 radial lines on the head.

There are exceptions, some ASTM A325 or SAE J429 Grade 5 bolts have been made of AISI C10B22. This material has only .22% Carbon but hardens due to the addition of .003% Boron. Heat Treating this material my prove difficult without accurate temperature control.


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