The head of a cross-recessed countersunk head screw is flat, countersunk, or semi-countersunk. Generally, countersunk head screws are cross-recessed. Countersunk head screws are generally used in electrical equipment, electronic machinery, mechanical equipment, household appliances, digital products, water conservancy projects, furniture, etc. In terms of materials, cross recessed countersunk head screws can be made of a variety of materials, such as carbon steel, stainless steel, alloy steel, etc. The choice of these materials depends on the specific application environment and requirements of the screw. For example, where higher strength and corrosion resistance are required, stainless steel or alloy steel materials are often chosen. Cross recessed countersunk head screws are available in different surface treatments, such as galvanized, nickel plated or phosphated, etc. to improve their corrosion resistance and service life. SCM435 belongs to alloy steel, belongs to the medium carbon steel series, and is a Japanese material grade.
The Specification Form of GB819 is as bellow
| GB819 | M | |||||||||||||
| D | 1.6 | 2 | 2.5 | 3 | 3.5 | 4 | 5 | 6 | 8 | 10 | ||||
| P | Pitch | 0.35 | 0.4 | 0.45 | 0.5 | 0.6 | 0.7 | 0.8 | 1 | 1.25 | 1.5 | |||
| a | max | 0.7 | 0.8 | 0.9 | 1 | 1.2 | 1.4 | 1.6 | 2 | 2.5 | 3 | |||
| dk | theor. | max | 3.6 | 4.4 | 5.5 | 6.3 | 8.2 | 9.4 | 10.4 | 12.6 | 17.3 | 20 | ||
| Actual | max=nominal size | 3 | 3.8 | 4.7 | 5.5 | 7.3 | 8.4 | 9.3 | 11.3 | 15.8 | 18.3 | |||
| min | 2.7 | 3.5 | 4.4 | 5.2 | 6.94 | 8.04 | 8.94 | 10.87 | 15.37 | 17.78 | ||||
| k | max=nominal size | 1 | 1.2 | 1.5 | 1.65 | 2.35 | 2.7 | 2.7 | 3.3 | 4.65 | 5 | |||
| r | max | 0.4 | 0.5 | 0.6 | 0.8 | 0.9 | 1 | 1.3 | 1.5 | 2 | 2.5 | |||
| x | max | 0.9 | 1 | 1.1 | 1.25 | 1.5 | 1.75 | 2 | 2.5 | 3.2 | 3.8 | |||
| Socket No. | 0 | 0 | 1 | 1 | 2 | 2 | 2 | 3 | 4 | 4 | ||||
| M1 | Ref. | 1.6 | 1.9 | 2.9 | 3.2 | 4.4 | 4.6 | 5.2 | 6.8 | 8.9 | 10 | |||
| M2 | Ref. | 1.6 | 1.9 | 2.8 | 3 | 4.1 | 4.4 | 4.9 | 6.6 | 8.8 | 9.8 | |||
| Penetration depth |
Type H | max | 0.9 | 1.2 | 1.8 | 2.1 | 2.4 | 2.6 | 3.2 | 3.5 | 4.6 | 5.7 | ||
| min | 0.6 | 0.9 | 1.4 | 1.7 | 1.9 | 2.1 | 2.7 | 3 | 4 | 5.1 | ||||
| Type Z | max | 0.95 | 1.2 | 1.73 | 2.01 | 2.2 | 2.51 | 3.05 | 3.45 | 4.6 | 5.64 | |||
| min | 0.7 | 0.95 | 1.48 | 1.76 | 1.75 | 2.06 | 2.6 | 3 | 4.15 | 5.19 | ||||
①The diameter of the unthreaded portion is approximately equal to the diameter of the pitch or allowed to equal the major diameter of the thread.
Product standard of this physical picture: GB819
Spec:M3-0.5*8 Strength Class：12.9Grade Material:SCM435 Surface treatment :heat treatment,Zinc Plated
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