An Introduction To Lathe types , Parts ,Uses ,Operations And Calculations
Introduction
The lathe is a machine tool used principally for shaping articles of metal (and sometimes wood or other materials) by causing the workpiece to be held and rotated by the lathe while a tool bit is advanced into the work causing the cutting action. The basic lathe that was designed to cut cylindrical metal stock has been developed further to produce screw threads. tapered work. drilled holes. knurled surfaces, and crankshafts. The typical lathe provides a variety of rotating speeds and a means to manually and automatically move the cutting tool into the workpiece. Machinists and maintenance shop personnel must be thoroughly familiar with the lathe and its operations to accomplish the repair and fabrication of needed parts.
Types of Lathes.
Lathes can be conveniently classified as engine lathes, turret lathes, and special purpose lathes. All engine lathes and most turret and special purpose lathes have horizontal spindles and, for that reason, are sometimes referred to as horizontal lathes. The smaller lathes in all classes may be classified as bench lathes or floor or pedestal lathes, the reference in this case being to the means of support
A- Engine Lathes.
The engine lathe is intended for general purpose lathe work and is the usual lathe found in the machine shop. The engine lathe may be bench or floor mounted; it may be referred to as a tool room-type lathe, or a sliding-gap or extension-type lathe. The engine lathe consists mainly of a head stock, a tail stock, a carriage, and a bed upon which the tail stock and carriage move. Most engine lathes are back-geared and high torque, which is required for machining large diameter workpieces and taking heavy cuts. The usual engine lathe has longitudinal power and cross feeds for moving the carriage. It has a lead screw with gears to provide various controlled feeds for cutting threads.
(1) Bench-Type Engine Lathe.
The bench-type engine lathe (figure 2 ) is generally powered by an electric motor, mounted to the bench behind the lathe head stock, and is driven by means of a flat leather belt. Some bench lathes use an underneath motor drive where the drive belt passes through a hole in the bench. This arrangement is convenient where space in the shop is limited. The bench type engine lathe is generally equipped with the necessary tools, chucks, lathe dogs, and centers for normal operation. The lathe may have a quick change gearbox for rapid change of threading feeds, or gears may have to be installed singly or in combination to achieve the proper threading feeds. The bench lathe may or may not have a power-operated cross feed drive.
(2) Floor-Mounted Engine Lathe
The floor-mounted engine lathe (figure 3) or pedestal-type engine lathe, is inherently more rigid than the bench-type lathe and may have a swing as great as 16 or 20 inches and a bed length as great as 12 feet, with 105 inches between centers. The drive motor is located in the pedestal beneath the lathe head stock. A tension release mechanism for loosening the drive belt is usually provided so that the drive belt may be quickly changed to different pulley combinations for speed changes. The head stock spindle is back-geared to provide slow spindle speeds, and a quick-change gearbox for controlling the lead screw is installed on all currently manufactured floor-mounted lathes. The floor-mounted engine lathe usually has a power-operated cross feed mechanism.
(3) Toolroom Lathe.
The toolroom lathe (figure 4 ) is an engine lathe equipped with more precision accessories and built to greater standards of accuracy than standard engine lathes. It may be either floor-mounted or a bench-mounted.
The toolroom-type lathe is usually supplied with a very precise lead screw for threading operations. It comes equipped with precision accessories such as a collet, chuck attachment, a taper attachment, and a micrometer stop. Therefore, work of a better class and of a more complete nature may be accomplished on a toolroom-type engine lathe
(4) Sliding Gap-Type Floor-Mounted Engine Lathe.
The sliding gap-type floor-mounted lathe or extension gap lathe contains two lathe beds, the top bed or sliding bed, and the bottom bed (figure 5 ). The sliding bed mounts the carriage and the tail stock and can be moved outward, away from the head stock as desired. By extending the sliding bed, material up to 28 inches in diameter may be swung on this lathe. The sliding bed may also be extended to accept between centers workpieces that would not normally fit in a standard lathe of the same size
B- Turret Lathes.
The turret lathe (figure 6) is a lathe used extensively for the high speed production of duplicate parts. The turret lathe is so named because it has a hexagonal turret, or multiple tool holder, in place of the tail stock found on the engine lathe. Most turret lathes are equipped with a pump and basin for the automatic application of a coolant or cutting oil to the work piece.
(1) Floor-Mounted Horizontal Turret Lathe.
The floor-mounted horizontal turret lathe (figure 7) is intended for quick turning of bar stock and chucked workpieces with a minimum amount of adjustments between operations. The lathe uses a collet chuck and a hollow headstock spindle for feeding bar stock into the machine, or may use a universal scroll chuck for swinging the workpiece.
C. Special Purpose Lathes
Some lathes have characteristics that enable them to do certain work well. Some of these lathes are of the heavy-production type where large numbers of identical parts must be produced to make the
operation more economical. Other special purpose lathes are specialized for machining specific items and cannot be adapted to the common types of lathe operations.
(1) Bench-type Jeweler's Lathe.
The bench-type jeweler's lathe (figure 9) is actually a miniature engine lathe designed for the precision machining of small parts. The usual jeweler's lathe contains a collet-type chuck, lead screw, change gears for threading operations, and a precise manual crossfeed. Controls and feeds are calibrated in smaller increments than with the engine lathe and, as a result, workpieces of small dimensions can
be machined to a great degree of accuracy. The jeweler's lathe is belt driven by an independent motor which can be mounted above or behind the lathe.
(2) Other Special Purpose Lathes.
Other special purpose lathes (figures 10,11) include the production lathe, the automatic lathe, the automatic screw machine, the brakedrum lathe, the crankshaft lathe, the duplicating lathe, the multispindle lathe, and lathes designed for turning car axles or forming sheet metal.
Lathe parts
Figure 12 provides a general illustration of the parts normally found on a lathe.
1. Bed
It is the main body of the machine. All main components are bolted on it. It is usually made by cast iron due to its high compressive strength and high lubrication quality. It is made by casting process and bolted on floor space.
2. Tool post
It is bolted on the carriage. It is used to hold the tool at correct position. Tool holder mounted on it.
3. Chuck
Chuck is used to hold the workspace. It is bolted on the spindle which rotates the chuck and work piece. It is four jaw and three jaw according to the requirement of machine.
4. Head stock
Head stock is the main body parts which are placed at left side of bed. It is serve as holding device for the gear chain, spindle, driving pulley etc. It is also made by cast iron.
5. Tail stock
Tail stock situated on bed. It is placed at right hand side of the bed. The main function of tail stock to support the job when required. It is also used to perform drilling operation.
6. Lead screw
Lead screw is situated at the bottom side of bed which is used to move the carriage automatically during thread cutting.
7. Legs
Legs are used to carry all the loads of the machine. They are bolted on the floor which prevents vibration.
8. Carriage
It is situated between the head stock and tail stock. It is used to hold and move the tool post on the bed vertically and horizontally. It slides on the guide ways. Carriage is made by cast iron.
9. Apron
It is situated on the carriage. It consist all controlling and moving mechanism of carriage.
10. Chips pan
Chips pan is placed lower side of bed. The main function of it to carries all chips removed by the work piece.
11. Guide ways
Guide ways take care of movement of tail stock and carriage on bed.
12. Speed controller
Speed controller switch is situated on head stock which controls the speed of spindle.
13. Spindle
It is the main part of lathe which holds and rotates the chuck.
Turning
In a lathe machine work, different operations require different types of lathe cutting tools, which are as follow,
1- According to the method of using the tool
1- Turning tool.
2- Chamfering tool.
3- Thread cutting tool.
4- Internal thread cutting tool.
5- Facing tool.
6- Grooving tool.
7- Forming tool.
8- Boring tool.
9- Parting-off tool.
10- Counter boring tool
11- Undercutting tool
2- According to the method of applying feed
Applications for the cutting tools are shown in Fig 23. and include turning, facing, threading, cutoff, boring, and inside threading.
HOW TO CENTRE THE CUTTING TOOL
Before any turning takes place it is common practice to check that the point of the lathe tool is centred. This means that the lathe tool point should be the same height as the tip of the tailstock centre. If this is not done and the tool point is either above or below the centre point - usually the finish to the steel will be poor. Also, a significant amount of vibration could take place during turning.
Introduction
The lathe is a machine tool used principally for shaping articles of metal (and sometimes wood or other materials) by causing the workpiece to be held and rotated by the lathe while a tool bit is advanced into the work causing the cutting action. The basic lathe that was designed to cut cylindrical metal stock has been developed further to produce screw threads. tapered work. drilled holes. knurled surfaces, and crankshafts. The typical lathe provides a variety of rotating speeds and a means to manually and automatically move the cutting tool into the workpiece. Machinists and maintenance shop personnel must be thoroughly familiar with the lathe and its operations to accomplish the repair and fabrication of needed parts.
Types of Lathes.
Lathes can be conveniently classified as engine lathes, turret lathes, and special purpose lathes. All engine lathes and most turret and special purpose lathes have horizontal spindles and, for that reason, are sometimes referred to as horizontal lathes. The smaller lathes in all classes may be classified as bench lathes or floor or pedestal lathes, the reference in this case being to the means of support
A- Engine Lathes.
The engine lathe is intended for general purpose lathe work and is the usual lathe found in the machine shop. The engine lathe may be bench or floor mounted; it may be referred to as a tool room-type lathe, or a sliding-gap or extension-type lathe. The engine lathe consists mainly of a head stock, a tail stock, a carriage, and a bed upon which the tail stock and carriage move. Most engine lathes are back-geared and high torque, which is required for machining large diameter workpieces and taking heavy cuts. The usual engine lathe has longitudinal power and cross feeds for moving the carriage. It has a lead screw with gears to provide various controlled feeds for cutting threads.
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| FIG 1 |
(1) Bench-Type Engine Lathe.
The bench-type engine lathe (figure 2 ) is generally powered by an electric motor, mounted to the bench behind the lathe head stock, and is driven by means of a flat leather belt. Some bench lathes use an underneath motor drive where the drive belt passes through a hole in the bench. This arrangement is convenient where space in the shop is limited. The bench type engine lathe is generally equipped with the necessary tools, chucks, lathe dogs, and centers for normal operation. The lathe may have a quick change gearbox for rapid change of threading feeds, or gears may have to be installed singly or in combination to achieve the proper threading feeds. The bench lathe may or may not have a power-operated cross feed drive.
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| FIG 2 |
The floor-mounted engine lathe (figure 3) or pedestal-type engine lathe, is inherently more rigid than the bench-type lathe and may have a swing as great as 16 or 20 inches and a bed length as great as 12 feet, with 105 inches between centers. The drive motor is located in the pedestal beneath the lathe head stock. A tension release mechanism for loosening the drive belt is usually provided so that the drive belt may be quickly changed to different pulley combinations for speed changes. The head stock spindle is back-geared to provide slow spindle speeds, and a quick-change gearbox for controlling the lead screw is installed on all currently manufactured floor-mounted lathes. The floor-mounted engine lathe usually has a power-operated cross feed mechanism.
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| FIG 3 |
(3) Toolroom Lathe.
The toolroom lathe (figure 4 ) is an engine lathe equipped with more precision accessories and built to greater standards of accuracy than standard engine lathes. It may be either floor-mounted or a bench-mounted.
The toolroom-type lathe is usually supplied with a very precise lead screw for threading operations. It comes equipped with precision accessories such as a collet, chuck attachment, a taper attachment, and a micrometer stop. Therefore, work of a better class and of a more complete nature may be accomplished on a toolroom-type engine lathe
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| FIG 4 |
(4) Sliding Gap-Type Floor-Mounted Engine Lathe.
The sliding gap-type floor-mounted lathe or extension gap lathe contains two lathe beds, the top bed or sliding bed, and the bottom bed (figure 5 ). The sliding bed mounts the carriage and the tail stock and can be moved outward, away from the head stock as desired. By extending the sliding bed, material up to 28 inches in diameter may be swung on this lathe. The sliding bed may also be extended to accept between centers workpieces that would not normally fit in a standard lathe of the same size
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| FIG 5 |
B- Turret Lathes.
The turret lathe (figure 6) is a lathe used extensively for the high speed production of duplicate parts. The turret lathe is so named because it has a hexagonal turret, or multiple tool holder, in place of the tail stock found on the engine lathe. Most turret lathes are equipped with a pump and basin for the automatic application of a coolant or cutting oil to the work piece.
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| FIG 6 |
(1) Floor-Mounted Horizontal Turret Lathe.
The floor-mounted horizontal turret lathe (figure 7) is intended for quick turning of bar stock and chucked workpieces with a minimum amount of adjustments between operations. The lathe uses a collet chuck and a hollow headstock spindle for feeding bar stock into the machine, or may use a universal scroll chuck for swinging the workpiece.
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| FIG 7 |
C. Special Purpose Lathes
Some lathes have characteristics that enable them to do certain work well. Some of these lathes are of the heavy-production type where large numbers of identical parts must be produced to make the
operation more economical. Other special purpose lathes are specialized for machining specific items and cannot be adapted to the common types of lathe operations.
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| FIG 8 |
(1) Bench-type Jeweler's Lathe.
The bench-type jeweler's lathe (figure 9) is actually a miniature engine lathe designed for the precision machining of small parts. The usual jeweler's lathe contains a collet-type chuck, lead screw, change gears for threading operations, and a precise manual crossfeed. Controls and feeds are calibrated in smaller increments than with the engine lathe and, as a result, workpieces of small dimensions can
be machined to a great degree of accuracy. The jeweler's lathe is belt driven by an independent motor which can be mounted above or behind the lathe.
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| FIG 9 |
(2) Other Special Purpose Lathes.
Other special purpose lathes (figures 10,11) include the production lathe, the automatic lathe, the automatic screw machine, the brakedrum lathe, the crankshaft lathe, the duplicating lathe, the multispindle lathe, and lathes designed for turning car axles or forming sheet metal.
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| FIG 10 |
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| FIG 11 |
Figure 12 provides a general illustration of the parts normally found on a lathe.
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| FIG 12 |
1. Bed
It is the main body of the machine. All main components are bolted on it. It is usually made by cast iron due to its high compressive strength and high lubrication quality. It is made by casting process and bolted on floor space.
It is bolted on the carriage. It is used to hold the tool at correct position. Tool holder mounted on it.
3. Chuck
Chuck is used to hold the workspace. It is bolted on the spindle which rotates the chuck and work piece. It is four jaw and three jaw according to the requirement of machine.
4. Head stock
Head stock is the main body parts which are placed at left side of bed. It is serve as holding device for the gear chain, spindle, driving pulley etc. It is also made by cast iron.
5. Tail stock
Tail stock situated on bed. It is placed at right hand side of the bed. The main function of tail stock to support the job when required. It is also used to perform drilling operation.
6. Lead screw
Lead screw is situated at the bottom side of bed which is used to move the carriage automatically during thread cutting.
7. Legs
Legs are used to carry all the loads of the machine. They are bolted on the floor which prevents vibration.
8. Carriage
It is situated between the head stock and tail stock. It is used to hold and move the tool post on the bed vertically and horizontally. It slides on the guide ways. Carriage is made by cast iron.
9. Apron
It is situated on the carriage. It consist all controlling and moving mechanism of carriage.
10. Chips pan
Chips pan is placed lower side of bed. The main function of it to carries all chips removed by the work piece.
11. Guide ways
Guide ways take care of movement of tail stock and carriage on bed.
12. Speed controller
Speed controller switch is situated on head stock which controls the speed of spindle.
13. Spindle
It is the main part of lathe which holds and rotates the chuck.
SPECIFICATION OF LATHE
The size of a lathe is generally specified by the following means:
(a) Swing or maximum diameter that can be rotated over the bed ways
(b) Maximum length of the job that can be held between head stock and tail stock centres
(c) Bed length, which may include head stock length also
(d) Maximum diameter of the bar that can pass through spindle or collect chuck of capstan lathe.
Figure 13. illustrates the elements involved in specifications of a lathe. The following data also contributes to specify a common lathe machine.
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| FIG 13 |
(i) Maximum swing over bed
(ii) Maximum swing over carriage
(iii) Height of centers over bed
(iv) Maximum distance between centers
(v) Length of bed
(vi) Width of bed
(vii) Morse taper of center
(viii) Diameter of hole through spindle
(ix) Face plate diameter
(x) Size of tool post
(xi) Number of spindle speeds
(xii) Lead screw diameter and number of threads per cm.
(xiii) Size of electrical motor
(xiv) Pitch range of metric and inch threads etc.
LATHE OPERATIONS
Operations, which can be performed in a lathe either by holding the workpiece between centers or by a chuck are :
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| FIG 14 |
1. Straight turning 2. Shoulder turning 3. Taper turning
4. Chamfering 5. Eccentric turning 6. Thread cutting 7. Facing
8. Forming 9. Filing 10. Polishing 11. Grooving 12. Knurling
13. Spinning 14. Spring winding
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| FIG 15 |
Operations (figure 15 ) which are performed by holding the work by a chuck or a face plate or an angle plate are:
1. Undercutting 2. Parting-off 3. Internal thread cutting 4. Drilling
5. Reaming 6. Boring 7. Counter boring 8. Taper boring 9. Tapping
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| FIG 16 |
Operations which are performed by using special lathe attachments are:
1. Milling 2. Grinding
Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates.
Tapering
Tapering is to cut the metal to nearly a cone shape with the help of the compound slide. This is something in between the parallel turning and facing off. If one is willing to change the angle then they can adjust the compound slide as they like.
Tapering
Tapering is to cut the metal to nearly a cone shape with the help of the compound slide. This is something in between the parallel turning and facing off. If one is willing to change the angle then they can adjust the compound slide as they like.
Chamfering
Chamfering is a cut on the edge or corner of something that makes it slope slightly rather than being perfectly square
Parting
The part is removed so that it faces the ends. For this the parting tool is involved in slowly to make perform the operation. For to make the cut deeper the parting tool is pulled out and transferred to the side for the cut and to prevent the tool from breaking.
Eccentric turning
Eccentric turning is one when a work is turned not on the normal center axis, instead it is done at an offset (as per the requirement). An engine crankshaft is the immediate example we can think of. Usually, general purpose lathe will have a three jaw chuck - which will take
care regular turning operations.
The part is removed so that it faces the ends. For this the parting tool is involved in slowly to make perform the operation. For to make the cut deeper the parting tool is pulled out and transferred to the side for the cut and to prevent the tool from breaking.
Eccentric turning
Eccentric turning is one when a work is turned not on the normal center axis, instead it is done at an offset (as per the requirement). An engine crankshaft is the immediate example we can think of. Usually, general purpose lathe will have a three jaw chuck - which will take
care regular turning operations.
Drilling
For producing holes in jobs on lathe, the job is held in a chuck or on a face plate. The drill is held in t
he position of tailstock and which is brought nearer the job by moving the tailstock along the guide
ways, the thus drill is fed against the rotating job
Thread cutting
Thread cutting on the lathe is a process that produces a helical ridge of uniform section on the workpiece. This is performed by taking successive cuts with a threading toolbit the same shape as
the thread form required.
Facing
Facing is the process of removing metal from the end of a workpiece to produce a flat surface. Most often, the workpiece is cylindrical, but using a 4-jaw chuck you can face rectangular or odd-shaped
work to form cubes and other non-cylindrical shapes.
Forming
The forming is an operation that produces a convex, concave or any irregular profile on the workpiece.s
Filing
Filing is a material removal process in manufacturing. Similar, depending on use, to both sawing and grinding in effect, it is functionally versatile, but used mostly for finishing operations, namely in deburring operations. Filing operations can be used on a wide range of materials as a finishing operation. Filing helps achieve workpiece function by removing some excess material and deburring
the surface. Sandpaper may be used as a filing tool for other materials, such as wood.
Knurling:
The knurling is a process of embossing (impressing) a diamond-shaped or straight-line pattern into the surface of workpiece. Knurling is essentially a roughening of the surface and is done to provide a
better gripping surface.
Reaming:
Reaming: The holes that are produced by drilling are rarely straight and cylindrical in form. The reaming operation finishes and sizes the hole already drilled into the workpiece.
Boring:
Boring: The boring operation is the process of enlarging a hole already produced by drilling.
Polishing
Polishing is finishing processes for smoothing a workpiece's surface using an abrasive and a work wheel or a leather strop. Technically polishing refers to processes that use an abrasive that is glued to the work wheel, while buffing uses a loose abrasive applied to the work wheel. Polishing is a more aggressive process while buffing is less harsh, which leads to a smoother, brighter finish. A common misconception is that a polished surface has a mirror bright finish, however most mirror bright finishes are actually buffed.
Grooving
The term grooving usually applies to a process of forming a narrow cavity of a certain depth, on a cylinder, cone, or a face of the part. The groove shape, or at least a significant part of it, will be in the
shape of the cutting tool. Grooving tools are also used for a variety of special machining operations.
Spinning
Metal spinning is a form of symmetrical metalworking where a flat circle, or circular, piece of metal is fitted into a hand lathe or CNC lathe. Held in place by a pressure pad, the metal disk is spun at an appropriate speed. A localized force utilizing a variety of rollers or tools is applied either by hand or by machine to gradually form the metal over a “chuck” or mandrel. In complex spinnings, multiple chucks may be used to accomplish a specific shape. Chucks are made from hardened metals or wood
For producing holes in jobs on lathe, the job is held in a chuck or on a face plate. The drill is held in t
he position of tailstock and which is brought nearer the job by moving the tailstock along the guide
ways, the thus drill is fed against the rotating job
Thread cutting
Thread cutting on the lathe is a process that produces a helical ridge of uniform section on the workpiece. This is performed by taking successive cuts with a threading toolbit the same shape as
the thread form required.
Facing
Facing is the process of removing metal from the end of a workpiece to produce a flat surface. Most often, the workpiece is cylindrical, but using a 4-jaw chuck you can face rectangular or odd-shaped
work to form cubes and other non-cylindrical shapes.
Forming
The forming is an operation that produces a convex, concave or any irregular profile on the workpiece.s
Filing
Filing is a material removal process in manufacturing. Similar, depending on use, to both sawing and grinding in effect, it is functionally versatile, but used mostly for finishing operations, namely in deburring operations. Filing operations can be used on a wide range of materials as a finishing operation. Filing helps achieve workpiece function by removing some excess material and deburring
the surface. Sandpaper may be used as a filing tool for other materials, such as wood.
Knurling:
The knurling is a process of embossing (impressing) a diamond-shaped or straight-line pattern into the surface of workpiece. Knurling is essentially a roughening of the surface and is done to provide a
better gripping surface.
Reaming:
Reaming: The holes that are produced by drilling are rarely straight and cylindrical in form. The reaming operation finishes and sizes the hole already drilled into the workpiece.
Boring:
Boring: The boring operation is the process of enlarging a hole already produced by drilling.
Polishing
Polishing is finishing processes for smoothing a workpiece's surface using an abrasive and a work wheel or a leather strop. Technically polishing refers to processes that use an abrasive that is glued to the work wheel, while buffing uses a loose abrasive applied to the work wheel. Polishing is a more aggressive process while buffing is less harsh, which leads to a smoother, brighter finish. A common misconception is that a polished surface has a mirror bright finish, however most mirror bright finishes are actually buffed.
Grooving
The term grooving usually applies to a process of forming a narrow cavity of a certain depth, on a cylinder, cone, or a face of the part. The groove shape, or at least a significant part of it, will be in the
shape of the cutting tool. Grooving tools are also used for a variety of special machining operations.
Spinning
Metal spinning is a form of symmetrical metalworking where a flat circle, or circular, piece of metal is fitted into a hand lathe or CNC lathe. Held in place by a pressure pad, the metal disk is spun at an appropriate speed. A localized force utilizing a variety of rollers or tools is applied either by hand or by machine to gradually form the metal over a “chuck” or mandrel. In complex spinnings, multiple chucks may be used to accomplish a specific shape. Chucks are made from hardened metals or wood
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| FIG 17 |
Lathe Cutting Tools
A lathe is a machine that rotates the workpiece about an axis of rotation to perform various operations such as turning, undercutting, knurling, drilling, facing, boring and cutting, with lathe cutting tools that are applied to the workpiece to create an object with symmetry about that axis.
For general purpose work, the tool used in is a single point tool, but for special operations, multipoint tools may use.
A lathe is a machine that rotates the workpiece about an axis of rotation to perform various operations such as turning, undercutting, knurling, drilling, facing, boring and cutting, with lathe cutting tools that are applied to the workpiece to create an object with symmetry about that axis.
For general purpose work, the tool used in is a single point tool, but for special operations, multipoint tools may use.
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| FIG 18 |
1- According to the method of using the tool
1- Turning tool.
2- Chamfering tool.
3- Thread cutting tool.
4- Internal thread cutting tool.
5- Facing tool.
6- Grooving tool.
7- Forming tool.
8- Boring tool.
9- Parting-off tool.
10- Counter boring tool
11- Undercutting tool
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| FIG 19 |
A Left-hand turning tool
B Round-nose turning tool
C Right-hand turning tool
D Left-hand facing tool
E Threading tool
F Right-hand facing tool
G Cutoff tool
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| FIG 20 |
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| FIG 21 |
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| FIG 22 |
Applications for the cutting tools are shown in Fig 23. and include turning, facing, threading, cutoff, boring, and inside threading.
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| FIG 23 |
HOW TO CENTRE THE CUTTING TOOL
Before any turning takes place it is common practice to check that the point of the lathe tool is centred. This means that the lathe tool point should be the same height as the tip of the tailstock centre. If this is not done and the tool point is either above or below the centre point - usually the finish to the steel will be poor. Also, a significant amount of vibration could take place during turning.
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| FIG 24 |
Turning operation calculations
Cutting speed. Cutting speed is given in surface feet per minute (sfpm) and is the speed of the workpiece in relation to the stationary tool bit at the cutting point surface. The cutting speed is given by the simple relation
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| FIG 25 |
and
where
S = cutting speed, sfpm or m/min
df = diameter of work, in or mm
rpm = revolutions per minute of the workpiece
When the cutting speed (sfpm) is given for the material, the revolutions per minute (rpm) of the workpiece or lathe spindle can be found from
and
Lathe cutting time. The time required to make any particular cut on a lathe may be found using two methods. When the cutting speed is given, the following simple relation may be used:
and
where
T = time for the cut, min
df = diameter of work, in or mm
L = length of cut, in or mm
F = feed, ipr (inches per revolution) or mmpr (millimeters per revolution)
S = cutting speed, sfpm (surface feet per minute) or m/min
Volume of metal removed. The volume of metal removed during a lathe cutting operation can be calculated as follows:
and
where
Vr = volume of metal removed, in³ or cm³
Cd = depth of cut, in or mm
F = feed, ipr or mmpr
S = cutting speed, sfpm or m/min
Machine power requirements
The following formula is for approximating machine power requirements for making a particular cut:
hp = dfSC
where
hp = required machine horsepower
d = depth of cut, in
f = feed, ipr
S = cutting speed, sfpm
C = power constant for the particular material
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