Fasteners Tips

Screws and bolts

Under normal circumstances the nominal diameter of less than 6mm screw means, and are presented with a screw thread integral (special cases up diameter 12mm), this is known as the screw thread means.

Nominal diameter greater than 6mm, and in a part of the threaded rod, the length of the threaded portion is generally twice the diameter of the rod, the screw means is typically referred to as a bolt.

2. Mechanical properties of fasteners rating

Bolt Intensity 3.6,4.6,4.8,5.6,5.8,6.8,8.8,9.8,10.9,12.9 ten levels.

Nuts Intensity 4,5,6,8,9,10,12 seven grades.

Bolts performance level code meaning: Digital tensile bolts left of the decimal representation of 1/100; digit after the decimal point (including decimal point) represents the ratio of the yield strength and tensile strength of the bolt. The yield strength and tensile strength of the unit is MPa (N / mm2).

Yield strength: The specimen during the tensile load does not increase or decrease the stress began to be able to continue to elongate the sample (deformation) when. The lower the yield strength of the steel, the force required for permanent deformation smaller, Jiyu easy forming.

Tensile strength: The tensile specimens, before pulling off withstand maximum stress. When the stress is greater than the tensile strength of the material suffered, will fracture, therefore, the greater tensile strength material, then it is better able to withstand large external stress without breaking.

3. strength bolts and nuts matching table:

Standard nut that nominal height ≥0.8D (nominal diameter)

4. Bolt performance rating and the materials and heat treatment

Performance

Grade material and heat treatment performance

Grade material and heat treatment

3.6 8.8 carbon steel or low carbon steel, carbon steel, hardened and tempered.

Mild steel or carbon steel 4.6 9.8

4.8 10.9 or low carbon steel, carbon steel or alloy steel, hardened and tempered.

5.6

5.8 12.9 alloy steel, hardened and tempered.

6.8

5. Mechanical properties of flat washers and spring washers

Mechanical properties of flat washers and spring washers are used to indicate the size of the hardness, flat washers with Vickers hardness (HV) expressed divided into Class C 100HV, A grade 140HV, 200HV, 300HV; spring washer is Rockwell Hardness (HRC) represented by (spring washer hardness range HRC42 ~ 50), under the same nominal diameter as the spring washers of different thickness, width and hardness divided into standard spring washer, spring washer light and heavy spring washer. For flat washer for surface treatment without treatment or zinc passivation; for spring washer for surface oxidation treatment, phosphate or zinc passivation.

Hardness is the resistance of material to imprint, scratches and other external forces. According to the test method Shore (Shore) Hardness (Sh A, etc.), Brinell (Brinell) Hardness (HB), Rockwell (Rockwell) hardness (HRC, etc.), Vickers (Vichers) hardness (HV) different. Durometer hardness values ​​and the type of Shore hardness tester is used to measure the hardness of the rubber.

6. Common hex bolts, nuts on the side of the old and new standard control width S

Thread S (mm)

The new standard within the old standard hex flange hexagon socket head

M3 5.5 5.5 / 2.5

M4 7 7/3

M5 8 8 8 4

M6 10 10 10 5

M8 14 13 13 6

M10 17 16 15 8

M12 19 18 18 10

M14 22 21 21 12

M16 24 24 24 14 (the old standard 12)

M18 27 27 / /

M20 30 30 30 17 (the old standard 14)

M22 32 34 / /

M24 36 36/19 (the old standard 17)

M30 46 46/22 (the old standard 19)

M36 55 55/27 (the old standard 24)

Note: The "old standard" means a standard promulgated in 1976.