How the screw works
Author: ComeFrom: Date:2020/7/2 9:09:44 Hits:123
What is a screw
It is well-known that when lifting heavy objects, it is easier to lift them vertically, use planks or iron plates, or use the inclined plane or the method of turning and moving. Also, it is easier to walk than steep and gentle slopes. In short, although the slope strength is small, the work performance is strong. So why does the inclined plane have such working performance? The vertical lift of the east and west requires more force in the opposite direction of gravity than its own gravity.
For example, when the object is placed on the inclined surface and is at rest, then gravity and force synthesis method can be considered separately as the right angle direction and the parallel direction of the inclined surface.
At a right angle to the inclined plane, the force of the same size as the surface but in the opposite direction acts to lift. Therefore, there is no need to consider the right-angle force when moving the inclined plane, only the force in the parallel direction. The force parallel to the inclined surface can lift things towards the inclined surface. If the inclined surface is smooth, the item will slip down.
If the slope is slightly uneven, friction will be generated, and the item will naturally rest on the slope. The ratio between the parallel force and the gravity of this surface is according to the force synthesis method. The height of the bottom of the horizontal plane and the right triangle are equal to the slope.
The smaller the inclination of the slope, the smaller the intensity. When the object moves along the inclined plane, it needs more force than the force parallel to the inclined plane. In this way, the use of the inclined surface can be easily moved even without gravity. However, the distance moved at this time is longer than the time it takes to lift vertically. If the slope of the slope is smaller, it can be lifted with a small force, and it takes a long distance to lift the same height. Everyone avoids the gentle right way when walking the mountain road, and chooses the narrow and steep as the near way to apply the slope function.
It is the screws and wedges that use these bevels. From the work point of view, the wedge is wrapped in a cylinder. Roll the elongated right-angled triangular paper, first sandwiching the long axis of the right-angled side into a right-angled state, the beveled side of the triangle draws a spiral on the rod. It is the screw that processes the groove shape along this spiral.
The groove part is called tooth valley, and the protrusion part is called tooth peak. The shaft of the rod is called the screw. In order to fit the peaks and valleys, it is the nut that processes the spiral groove inside the round hole. Generally, screws and nuts are matched to work. The distance that the tooth peak moves in the direction of the axis when the screw rotates once around the axis is called read. Including the cross section of the screw axis, the distance measured by the point corresponding to the adjacent tooth peaks parallel to the axis is called the pitch.
The screw has such a structure, so its working performance is the same as that of the inclined plane. That is to say, the ability to move along the inclined surface means that the rotation of the screw is consistent, and the action of the screw shaft part can be proved if it can be lifted. Therefore, increase the force in the direction of the screw rotation and increase the force in the axis direction. It can be said that the screw is wound around the inclined surface, and the inclination of the inclined surface is smaller, the corresponding pitch becomes smaller. The working performance of the small slope is strong, and the screw force of the small pitch becomes stronger. However, the excessively small pitch makes it easy to damage the screw when tightening the tooth peak, and the screw is easy to break. Therefore, the size of the pitch can be appropriately determined according to the method of use or the material and thickness of the rod.
The screws are standardized in the JIS standard. However, it does not mean that all specifications are produced or stocked. On the other hand, although there are no specifications, they will be manufactured according to demand. If the order quantity is more than hundreds of thousands, it can be specially corresponded, but if there are thousands or less, the price is more expensive. For example, boron steel for high-pressure screws for construction, upset head screws for automobiles, self-tapping screws, etc. are out of specifications but are used in mass production. On the other hand, the screw peaks used in aircraft are American specifications, and the plating is chromium passivation. These are very expensive because of the small number. The precision of the screws used in the machine is generally 6g, 6H, and the pitch is usually large screws except for the small screws used in automobiles. It is also possible that the screws used for plastic products do not use standard tooth shapes.
In addition to general screws, there are self-tapping screws.