METRICS

METRICS

BOLT STRENGTH IDENTIFICATION

ENGLISH SYSTEM

Grade 1 or 2 Grade 5 Grade 8

English bolts: Identification marks on the bolt head represent Rockwell hardness. Generally, the bolt’s grade is equal to the number of marks plus two. The higher the grade, the stronger the bolt.

METRIC SYSTEM

4.6 4.8 5.8 8.8 9.8 10.9

Metric bolts: Identification class numbers on bolt heads represent tensile strength. Higher numbers indicate stronger bolts. Common metric fastener bolt strength properties are 9.8 and 10.9.

HEX NUT STRENGTH IDENTIFICATION

ENGLISH SYSTEM METRIC SYSTEM

Grade 5 Grade 8

Identification dots represent Rockwell hardness. The Identification class numbers on nuts represent tensile nut’s grade is equal to the number of dots plus two. strength. Higher numbers indicate stronger nuts. Nuts The higher the grade, the stronger the nut. may also have blue finish or paint daub on hex flat.

OTHER TYPES OF PARTS

Metric identification schemes vary by type of part, most often a variation of that used for bolts and nuts. Note that many types of English and Metric fasteners carry no special identification if they are otherwise unique.

9

– Stamped U-Nuts

2 MET CLASS CLASS CLASS

10.9 9.8 8.8

–Tapping, thread forming and certain –Studs, Large studs may carry the property class number. other case hardened screws. Smaller studs use a geometric code on the end.

Revision 1, 8/10/2000