Tips on the use of screws and nuts

Precautions for product use: Stainless steel and carbon steel have essential differences. Stainless steel has better ductility. Improper use will cause the screw and the 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 correct product:

(1) Confirm whether the mechanical properties of the product can meet the requirements before use

(2) The length of the bolt should be selected appropriately, based on the 1-2 pitch of the exposed nut after tightening.

2. Reduce friction coefficient:

(1) The thread must be kept clean;

(2) Add lubricant appropriately before use

3. The correct method of operation:

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

(2) During the tightening process, the force must be even, and the force must not exceed the safe torque value

(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 quickly when used, so as to avoid the rapid rise of temperature and cause lockup.

4. Safety torque reference table: (Guide: Hydrogen embrittlement after heat treatment of fasteners)

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

(2) Performance grade of screws and nuts; A2-70, 304 material, tensile strength: 700N/m㎡, yield strength: 450N/m㎡;

(3) Operation mode: Clamp the screw head vertically on a bench vise, clamp a piece of work, a flat washer and a spring washer in the middle, and then put on the nut to apply force evenly, which is used as a nut for the 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 40409 Note: The above data is based on the above experimental conditions and is for reference only. The actual data is affected by the construction conditions, but the maximum torque should not be exceeded.

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