Basic knowledge of standard parts

Precautions for product use:

Stainless steel is essentially different from carbon steel. Stainless steel has good ductility. Improper use will cause the screw and the nut to be unable to unscrew after being matched. It is commonly known as "locked up" or "killed".

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, based on the 1-2 pitch of the exposed nut 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 perpendicular to the axis of the screw, and 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 rapidly during use, so as to avoid the rapid rise of temperature and cause lockup (such as electric wrenches, etc.).

4. Safety torque reference table:
(1) Use equipment: torque wrench, bench vise, matching sleeve:
(2) Performance grade of screws and nuts;
A2-70, 304 material, tensile strength: 700N/mm2, yield strength: 450N/mm2;
(3) Operation mode: Clamp the screw head vertically on a bench vise, clamp a workpiece, a flat washer and a spring washer in the middle, and then put on the nut to apply force evenly, as the force applied to the nut reaches the following At the value, the nut can no longer be unscrewed smoothly.

(4) Safety torque table: unit: N.m
Specifications M20-2.5M18-2.5M16-2.0M14-2.0M12-1.75
Safe torque 220 180 150 100 55
Specification M10-1.5M8-1.25M6-1.0
Safe torque 40409