Lathe Machine

1.1 History Of Lathe Machine 

The lathe machine is said to be the mother of all machine tools. Centuries ago, from the earliest periods of human development, when the simplest form of this While many means of holding and rotating the job in the lathe machine came into existence, there were also many clumsy ways of cutting bangles with its help. In the 19th century, French watchmakers were able to cut specific pitches on wide lathes.While many means of holding and rotating the job in the lathe machine came into existence, there were also many clumsy ways of cutting bangles with its help. In the 18th century, French watchmakers were able to cut specific pitches on wide lathes.

At the beginning of the 19th century, Henry Maudsley built a sliding carriage lathe machine, on the basis of which he was able to cut 16 to 100 per inch (1.5 mm to 0.25 mm pitch) and was called the founder of the lathe machine. This lathe driven by lead screws and gears. The machine played an important role in the industrial development of that time. The interesting thing is that the invention of James Watt's Engine was also in its early stages. Total parts of Watt's engine were turned on this ancestral lathe of machine tools. Because of this it is still known as engine lathe till today.

1.2. Definition of Lathe Machine:

                        A lathe is a general purpose machine tool that is used for turning round jobs externally and internally. In this machine the job rotates on its horizontal axis. While a single-point cutting tool does the turning of the job by moving forward gradually. Apart from this, many more tasks can be done with the help of various work holding devices and tools used on the lathe machine. Such as drilling, boring, taper. Turning, screwing, turning, milling grinding, tapping and reaming etc.

        

 

1.3. Construction of Lathe Machine:

The construction of lathe machines, and  its working principle, work holding devices and functions used on it. It is a machine tool used in general industry or in vertical workshops. Such machine tools that are used for general tasks within general workshops are called general purpose machine tools. The principles of making such machines are also almost the same. In this group of machines come lathe machine and burma machine shaper, plus grinding machine and milling machine while special purpose machines can only do specific work like broaching machine, hobbing machine lapping. Machines etc. Machines of this group work according to specific needs. When modifications are made to ordinary machines for their specific purposes, these are called orthodox machine tools.
     Basically two operations of lathe machine are common, the first process is called parallel turning while the second is facing
1. Parallel Turning:
When a job is being turned in a cylindrical shape on a lathe, it is called parallel turning. In this process, the turning tool of the lathe takes a feed parallel to the machine axis. And the job turns parallel to the length direction.

2. Facing;

         When the turning tool is machining the end of the job, it is called facing. In this, the feed of the

 tool is perpendicular to the machine axis. At each cut, the distance of the tool is perpendicular to the

 central axis. If the tool takes a diagonal feed along the axis, it For facing, the cross slide of the lathe

 works perpendicular to the axis. The carriage remains stationary, while for parallel turning, the carriage

 moves parallel to the universal axis.

1.4 .Five Major Parts of Lathe Machine

     By the way, the lathe machine consists of many small and big parts. To understand the construction

 of the lathe machine, we first read about its five parts.

           1. Headstock   2. Bed   3. Tail stock   4. Carriage   5. Feeding and thread cutting system

1. Headstock:

     The headstock is located on the left hand side of the lathe. It is the most important part of the lathe. 

It has a system for holding the job, rotating it and providing multiple speeds. Its body is made 

of cast iron.

On both sides of its box-like body, spindle supporting bearings are fitted. In which the hollow spindle 

can rotate clockwise and counter-clockwise. Non-gear head stock has gears around the spindle. These

 gears are supported by levers. Different speeds are obtained from the change. These gradual speeds of

 the chuck or spindle are in Geometric The maximum number of spindle revolutions per minute is to

 machine a minimum diameter job on the machine, while the minimum number of revolutions per minute

 is to machine a diameter job greater than the maximum capacity of the lathe. Between these two limits 

The desired number of cycles per minute is set in step-by-step geometric progression. The spindle is

 made of steel. While a thick threads is cut on the outside so that the chuck or face plate can be tightened.

 On which the chuck is inserted with the help of bolts or cam nuts. In fact, there is a risk of opening the 

wide chuck by turning upside down. Only Morse Taper is cut. Older style headstocks have cone pulleys 

to achieve different speeds. These pulleys change the belt changing speed. Such headstocks also have a

 back gear which sets the spindle speed as well as being very heavy. are implemented for tasks.

Bed:

The bed of the lathe machine is made of cast iron. Bed strength, straightness, parallelism, resistance to

 vibration during work, and scraping after grinding of bed ways are its merits, so that the headstock,

 carriage, tailstock  can be aligned and their alignment is the same. Bed ways are called the foundation of

 the machine. To increase the strength and stiffness of the bed, both sides are strengthened with ribs. 

Bed ways are of two types: external bed ways. The carriage is supported and aligned and the tailstock is

 clamped on the inner bed ways.

 Tail Stock:

The tail stock is at the right end of the bed. It can be tightened anywhere according to the length of the

 job. The tail stock supports the right end of the job with a dead center. The tail stock body consists of

 two parts. The spindle at the top moves back and forth with the screw. The tail stock wheel is turned to

 rotate the screw. There is a straight hand width on the screw. The screw is turned enough to pull out the

 center. The spindle goes in and the center is pushed out by the screw. A bolt is attached to tighten the

 spindle.

Carriage:

Between the headstock and the tailstock, the bed ways moves back and forth by hand or by automatic feed. The carriage slides on the external ways of the bed ways. The bed has an H-shaped saddle. The cross slide on the saddle is perpendicular to the machine axis. Compound slide is fitted on cross slide. Tool post on compound slide. Apron on lower side in front of saddle. Apron has feeding system and half nut.

                              

1: Apron:

It is the front part of the carriage. It is driven by the rack A attached to the bed of the lathe. the carriage moves by rotating the carriage handwheel. This is called manual feed. Also, a fine clean shaft. The feed rod passes through the apron and the feed shaft rotates with the gears attached to the main spindle. A long key way is cut on this feed shaft. Due to which the drive carriage reaches the apron. And the carriage automatically moves right or left. This is called Automatic longitudinal feed. Thanks to this feeding system, the cross slide is fed automatically. is connected to the system. And this automatic movement of the cross slide is called Automatic cross feed. There are two levers in the apron to apply the feeds. A long wide lead screw is attached to the feed. It passes through the half nut of the apron. The half nut lever is operated to engage and disengage the half nut with the lead screw. . The lead screw gets drive from the main spindle. This drive is achieved by changing several sets of gears for different pitches of the bars. So that the desired width can be cut. The half nut is assisted by the chasing dial to engage the lead screw. is achieved. Actually this dial tells the exact time to actuate the half nut lever

2: Saddle:

It is like an English letter H above the bed ways. It acts as a bridge to the ways on both sides. Below it

 are sliding ways on the bed. It moves back and forth on the outer ways of the bedways. The bed ways

 are well Gibbed to fit the gap created by the indentation process. The saddle also has a locking bolt to

 lock the carriage. The cross slide on the saddle moves perpendicular to the machine axis. This

 movement can also be combined with automatic feeding

1.5. Feeding and Threading System:

You have read about the feeding system in the article of Apron. While for threading, the lead screw is

 attached to the spindle with the help of different sets of gears. The set of gears depends on the pitch to

 be cut and the pitch of the lead screw.

Graduated Collars:

The movements of compound slide and cross slide are due to the screws inside them. When the hand 

wheel of the slide is turned round, the ends of the screws have knobs on them while the nut is tightened

 with the slide. Graduated collars are fitted as shown below. Their collar circumferences are divided 

equally into multiple sections, starting at zero. If the movement is known, it becomes very easy to make 

an accurate measurement, knowing that twice the diameter of the cut depth is reduced in one cut.

To find the measurement of the smallest part of these collars, the pitch of the screws is divided by the

 total parts of the collar. For example, if the pitch of the screws is five mm and the collar is divided into 

100 equal parts

One division of collar  =5/100 =0.5

That is, to sink the tool in 0.05 mm, the wheel will be rotated by a small portion of the collar. This will

 reduce the diameter of the job by 0.10 mm. The linear movement of the slide on rotating the wheel one

 cycle will easily keep the steel roll together. Because screw pitch is always in whole millimeters.

Centers of lathe machine:

The centers of the lathe machine are very important because the accuracy of the work depends on them.

 The shanks of the centers are ground according to the morse taper. Their point angle is 60 degree. If

 heavy work is to be turned on the lathe. This angle can be 75 or 90 degree. Generally, this point is done

 by attaching the grinder to the compound slide at 60 degree. The compound slide is attached at

 30 degree at this time. .

Live Centre:

The center which supports the rotating job in the main spindle is called live center.

Dead Center:

The center which is placed in the tail stock is called dead center