ISO 898-1:2013, Table 3
Stamped 4.8. Low or medium carbon steel, fully or partially annealed.
| Size range | Proof | Yield min | Tensile min | Core hardness |
|---|---|---|---|---|
| d = 1.6 mm and up; no upper bound is published by the sources read here | 310 MPa (45 ksi) | 340 MPa (49 ksi) | 420 MPa (61 ksi) | Rockwell B71 to B95 |
Inch grades are published in ksi and metric classes in MPa. The other column on every row is a conversion at 1 ksi = 6.894757 MPa, rounded to the nearest whole unit - it is arithmetic on the published figure, not a second published figure.
The class number 4.8 stamped on the head, with the manufacturer's identifier.
The two numbers are the strength, not a serial number. The first times 100 is the nominal tensile strength in MPa; the two multiplied together times 10 is the nominal yield. Class 8.8 is 800 MPa tensile and 640 MPa yield, and you can read that straight off the head. Nominal tensile 400 MPa; yield 0.8 of it, so 320 MPa nominal, 340 MPa minimum.
Count the radial lines and add two. That rule identifies exactly two grades - SAE Grade 5 with three lines and SAE Grade 8 with six - and it fails everywhere else. Grades 1, 2 and 4 carry no marking at all, so an unmarked head is not evidence of Grade 2; it is evidence of nothing, and unmarked hardware that meets no standard looks exactly the same. ASTM grades are stamped with the specification (A325, A490, BC, BD, 307A) rather than lines, and metric classes are stamped with the class number. Four marking systems share one bin.
Low or medium carbon steel, fully or partially annealed. Light-duty fasteners, often cold formed.
Metric classes are marked with a number, not a line count. There is no metric equivalent of the radial-line system.
None of the sources cross-checked here states an upper diameter for this class, so none is printed. ISO 898-1 tabulates coarse-thread fasteners from M1.6 up; above the sizes a supplier actually stocks, ask for the certification rather than reading a chart.
Over d = 1.6 mm and up; no upper bound is published by the sources read here, ISO property class 4.8 requires a minimum tensile strength of 420 MPa (61 ksi), a minimum yield of 340 MPa (49 ksi) and a proof load of 310 MPa (45 ksi).
The class number 4.8 stamped on the head, with the manufacturer's identifier.
Low or medium carbon steel, fully or partially annealed. Light-duty fasteners, often cold formed.
Twenty-two grades and classes: the SAE J429 inch grades, five ASTM specifications and the ISO 898-1 property classes. It is not every grade in circulation. Stainless classes (ISO 3506 A2 and A4, ASTM F593), the ASTM A193 and A320 high and low temperature grades, ASTM F1554 anchor rod grades and SAE grades 3, 5.1 and 8.1 are not carried here.
Dimensions are as defined by ISO 898-1:2013, Table 3. This site is an independent reference and is not affiliated with, endorsed by or approved by any standards body.
Every value on this page was cross-checked against 3 independent published sources:
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