ASTM F568M Specification

This specification covers chemical and mechanical requirements for nine property classes of carbon and alloy steel externally threaded metric fasteners in nominal thread diameters M1.6 through M100 suited for use in general engineering applications. This specification does not cover dimensional requirements for fasteners of any property class. When referencing this specification for procurement purposes, it is mandatory that size, type, style, and any special dimensions of the product be additionally specified. In case of any conflict in requirements, the requirements of the individual product specification shall take precedence over those of this general specification. The purchaser may specify additional requirements which do not negate any of the provisions of this general specification or of the individual product specification. Such additional requirements, the acceptance of which are subject to negotiation with the supplier, must be included in the order information.

Chemical Composition


Property Class
Nominal Product Diameter, mm
Material and Treatment		 Product Analysis Element (% by weight)
Tempering Temperature, °C
C Mn B P S
Min Max Min Min Max Max Min
4.6 M5-M100 low or medium carbon steel ... 0.55 ... ... 0.048 0.058 ...
4.8 M1.6-M16 low or medium carbon steel, partially or fully annealed as required ... 0.55 ... ... 0.048 0.058 ...
5.8 M5-M24 low or medium carbon steel,cold worked 0.13 0.55 ... ... 0.048 0.058A ...
8.8 M20-M80 medium carbon steel, productis quenched and tempered B 0.25 0.55 ... ... 0.048 o.058c 425
8.8 M20-M36 low carbon martensite steel,productis quenched and temperedD 0.15 0.40 0.74 0.0005 0.048 0.058 425
8.8.3 M20-M36 atmospheric corrosion resistant steel, productis quenched and tempered ... ... ... see Table 2 ... ... 425
9.8 M1.6-M16 medium carbon steel, productis quenched and tempered 0.25 0.55 ... ... 0.048 0.058 425
9.8 M1.6-M16 low carbon martensite steel,product is quenched and temperedD 0.15 0.40 0.74 0.0005 0.048 0.058 425
10.9 M5-M20 medium carbon steel,product is quenched and temperedE,F 0.25 0.55 ... ... 0.048 0.058 425
10.9 M5-M100 medium carbon alloy steel, product is quenched and temperedE 0.20 0.55 ... ... 0.040 0.045 425
10.9 M5-M36 low carbon martensite steel, product is quenched and tempered E,F 0.15 0.40 0.74 0.0005 0.048 0.058 340
10.9.3 M16-M36 atmospheric corrosion resistant steel,productis quenched and tempered E ... ... ... see Table 2 ... ... 425
12.9 M1.6-M100 alloy steel,productis quenched and temperedE,G 0.31 0.65 ... ... 0.045 0.045 380
Note:

A. For studs only, sulfur content may be 0.33 %, max.
B. At the manufacturer’s option, medium-carbon-alloy steel may be used for nominal thread diameters over M24.
C. For studs only, sulfur content may be 0.13 %, max.
D. Products made using this material shall be specially identified as specified in Section 15.
E. Steel for Classes 10.9, 10.9.3, and 12.9 products shall be fine grain and have a hardenability that will achieve a structure of approximately 90 % martensite at the center of a transverse section one diameter from the threaded end of the product after oil quenching.
F. Carbon steel may be used at the option of the manufacturer for products of nominal thread diameters M12 and smaller. When approved by the purchaser, carbon steel may be used for products of diameters larger than M12 through M20, inclusive.
G. Alloy steel shall be used. Steel is considered to be alloy by the American Iron and Steel Institute when the maximum of the range given for the content of alloying elements exceeds one or more of the following limits: manganese, 1.65 %; silicon, 0.60 %; copper, 0.60 %; or in which a definite range or a definite minimum quantity of any of the following elements is specified or required within the limits of the recognized field of constructional alloy steels: aluminum, chromium up to 3.99 %, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium, or any other alloying elements added to obtain a desired alloying effect.

Mechanical Properties for Bolts, Screws, and Studs

Property Class Nominal Diameter of Product Full Size Bolts, Screws, and Studs Machined Test Specimens of Bolts, Screws, and Studs Surface Hardness Product Hardness

Proof LoadA		 Tensile Strength, MPaA Yield Strength, MPaB Tensile Strength, MPa Elongation, % Reduction of Area, % Rockwell 30N Rockwell Vickers
Length Measurement Method, MPa Yield Strength Method, MPa Min Min Min Min Min Max Min Max Min Max
4.6 MS-M100 225 240 400 240c 400 22 35 ... 867 895 120 220
4.8 M1.6-M16 310 340 420 340 420 14 35 ... B71 895 130 220
5.8 M5-M24D 380 420 520 420 520 10 35 ... 882 895 160 220
8.8 M20-M80 600 660 830 660 830 12 35 53 C23 C34 255 336
8.8.3 M20-M36 600 660 830 660 830 12 35 53 C23 C34 255 336
9.8 M1.6-M16 650 720 900 720 900 10 35 56 C27 C36 280 360
10.9 MS-M100 830 940 1040 940 1040 9 35 59 C33 C39 327 382
10.9.3 M16-M36 830 940 1040 940 1040 9 35 59 C33 C39 327 382
12.9E M1.6-M100 970 1100 1220 1100 1220 8 35 63 C38 C44 372 434
Note:

A. Proof load and tensile strength values for full size products of each property class.
B. Yield strength is stress at which a permanent set of 0.2 % of gage length occurs.
C. Yield point shall apply instead of yield strength at 0.2 % offset for Class 4.6 products.
D. Class 5.8 applies only to bolts and screws with lengths 150 mm and shorter and to studs of all lengths.
E. Caution is advised when considering the use of Class 12.9 bolts, screws, and studs. Capability of the bolt manufacturer, as well as the anticipated in-use environment, should be considered. High-strength products of Class 12.9 require rigid control of heat-treating operations and careful monitoring of as-quenched hardness, surface discontinuities, depth of partial decarburization, and freedom from carburization. Some environments may cause stress corrosion cracking of nonplated as well as electroplated products.