Common sense of basic use of standard parts

Precautions for product use: Stainless steel and carbon steel have essential differences. Stainless steel has better ductility. Improper use will cause the screw and nut to be unable to unscrew after being matched. It is commonly known as locked or bitten. The improvement of locking can mainly be considered from the following aspects:

1. Choose the right product:

(1) Before use, confirm whether the mechanical properties of the product can meet the use requirements (such as the tensile strength of the bolt and the safety load of the nut);

(2) The length of the bolt should be selected appropriately, and the screw nut shall be exposed to 1-2 pitches after tightening.

2. Reduce friction coefficient:

(1) The thread must be kept clean;

(2) Appropriately add lubricant (such as: 40# engine oil, butter) before use.

3. The correct method of operation:

(1) The nut must be screwed perpendicularly to the axis of the screw, do not tilt;

(2) During the tightening process, the force must be uniform, and the force must not exceed the safe torque value (safe torque table attached);

(3) Use torque wrenches or socket wrenches as much as possible, and avoid using adjustable wrenches or electric wrenches;

(4) It must be cooled when used under high temperature, and do not rotate fast when using, so as to avoid the rapid rise of temperature and cause lockup (such as electric wrenches, etc.). (Guide: General knowledge of wire)

4. Safety torque reference table:

(1) Equipment used: torque wrench, bench vise, matching sleeve:

(2) Performance grade of screws and nuts; A2-70, 304 material, tensile strength: 700N/mm², yield strength: 450 N/mm²;

(3) Operation mode: Clamp the screw head vertically on a bench vise, clamp a work piece, a flat washer and a spring washer in the middle, and then put on the nut to apply force evenly, as a nut When the force reaches the following value, the nut can no longer be unscrewed smoothly.

(4) Safety torque table: Unit: Nm Specification M20-2.5 M18-2.5 M16-2.0 M14-2.0 M12-1.75 Safety torque 220 180 150 100 55 Specification M10-1.5 M8-1.25 M6-1.0 Safety torque 40 40 9 Note: The above data are based on the above experimental conditions and are for reference only. The actual data is affected by the construction conditions, but the maximum torque should not be exceeded.

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