Greetings to the whole community of steemit and steemstem, this time I will talk about the machines and their elements, this is a very broad topic but I will try to address the most important to provide as much information as possible. I hope you enjoy it.

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The machines and the apparatuses are composed of several components that are assembled to form, first, groups and mechanical subassemblies and, later, the whole machine or apparatus.

UNION AND FIXING ELEMENTS
They are responsible for keeping the pieces or groups and subassemblies of a machine or apparatus together, which allows their assembly and disassembly.

Threaded connections:
They are all those that join one or more pieces by means of a thread.
Threaded connections can only be assembled and disassembled by turning the screw with respect to the nut or vice versa, this fundamental property is due to the self-retention effect produced by the friction and ensures that these joints do not loosen by themselves.

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JOINTS BETWEEN AXLES AND WHEELS
The union between an axle and a wheel is one of the most frequent that we can observe in machines. In some cases this union only fixes the two pieces together, while at other times it must transmit important torques, as in the case of the joint between the drive shaft and the drive wheel of the cars.

The forces can be transmitted by means of shapes in the parts that impede relative movement or by means of friction forces.

Unions by Form: Cotter Pins, Striae and Pins:
The conepto of the key is simple: a longitudinal groove is made in the axis, another longitudinal slot in the wheel, and between them a piece intervenes that blocks the relative movement between the two parts.

The fluted joints are based on longitudinal grooves made on the shaft, which connect with complementary grooves in the hole of the wheel.

In some applications the splined axes allow the axial sliding of the wheels, maintaining the transmission of the rotation movement.

The pins are small cylindrical or slightly conical metallic pieces that are inserted in a through hole that crosses the two pieces that must be joined. In some cases the pins are made in sheets or wires bent at their ends to prevent them from moving out.

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Unions by force:
In these joints, the torque is transmitted by means of the frictional forces between the wheel and the shaft as they are tightened between them. there are unbreakable force connections in which the diameter of the shaft is slightly greater than that of the wheel.

FRICTION BEARINGS
They are elements of machines whose function is the guidance of rotation of a piece.
In friction bearings, guiding is achieved by direct sliding between two cylindrical surfaces, while in the bearings said function is achieved by interposition of various rolling elements between said surfaces.
Friction bearings are rings usually made of bronze or a plastic metal that slide on a steel surface of sufficient hardness, instead, the bearings are formed by one or more rows of rolling elements generalente distanced from each other by a cage, the which roll between the inner ring, which is attached to the shaft, and the outer ring, which can be attached to a wheel or to the housing of the machine.

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Given the length of this topic, in a future publication I will continue talking about the machines and their elements in a second part. I hope it has been to your liking. Greetings and thank you!

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References:

Faires V. 1970. Diseño de Elementos de Máquinas. Montaner y Simon S.A.

Revista Mecánica Popular. Edición de 1972. Editorial América, S.A.

If you want to know more about this topic you can visit the following page:

https://iesvillalbahervastecnologia.files.wordpress.com/2010/04/elementos-de-maquinas-y-sistemas.pdf