Lathes are popular machining tools that consist of a high-speed rotating workpiece and a cutting tool mounted on the tool post that can be moved along X and Z axis.
These machines can be used for performing various operations such as turning, boring, threading, drilling, knurling, etc.
However, different operations require different tools, and changing the tool for each operation increases the cycle time.
Turret lathe is a modification of conventional lathes, that overcomes this issue and increases productivity by reducing the cycle time.
So what makes turret lathes special and what benefits do they offer over other lathes?
In this article, I have discussed Turret lathes in detail by talking about their parts, features, and types.
In the end, I've also compared turret lathes with capstan lathes and engine lathes to shed some light on the benefits of using turret lathes.
What is a Turret Lathe?
A Turret lathe is a modified version of traditional metal lathes, in which the tool post is replaced by a gun-like turret that can be rotated about its vertical axis. Generally, the turret holds six cutting tools that can be used to perform multiple machining operations in a single session.
Traditional lathes hold a single cutting tool that can be used to perform a particular machining operation by moving it along the lathe axes, thereby increasing the tool change time and reducing the productivity of the process.
The rotating turret eliminates the need to halt the process and change the cutting tool of lathe to perform different machining operations, thereby improving productivity.
important Parts of turret lathe
The important parts of a Turret lathe machine are:
Turret
The turret is a hexagonal tool holder that can rotate about its vertical axis and is mounted on a saddle. Every face of the turret has four tapped holes to fix the attachments.
It can hold up to six tools, and the turret can be rotated to access the tools required for different machining operations like turning, boring, knurling, etc.
Furthermore, the saddle can be moved along the horizontal axis to advance the cutting tool towards the workpiece.
For example, turning and tapping a hollow aluminum cylinder requires two different cutting tools to complete the machining process.
In this case, a turning tool is used to perform the turning operation, and then the turret can be rotated to access the tapping tool and perform the tapping operation.
The turret sits on a freely movable bearing so that it can be turned around by an operator to change the position of the tools after the clamps are released.
headstock
The headstock of the turret lathe is where all the driving mechanisms are present.
It houses all the controls of the lathe, such as start, stop, speed control, etc.
Depending upon the type of drive system, headstocks can be of two types: electric headstock and geared headstock.
In an electric headstock, the spindle speed variation is achieved by controlling the speed of the electric motor.
Electric headstock provides better speed control at the cost of torque and is generally used for applications where small workpieces are to be machined.
On the other hand, geared headstocks consist of special gear configurations to vary the spindle speed.
The geared mechanism reduces the spindle speed by increasing its torque, thereby making it ideal for machining workpieces with larger diameters.
This type of headstock is generally found in larger lathes that are used for performing comparatively deeper cuts in hard materials.
driving clutch
Similar to the clutch of an automobile, the driving clutch of turret lathe is used to couple and de-couple the prime-mover and spindle. Prime-mover can be a motor or a gear-coupled shaft.
In the ideal state, the prime mover and the spindle are de-coupled, and you can use the driving clutch to engage them before beginning the machining operation.
tool post
Tool post is used to mount the cutting tools in a Turret lathe.
It can move in the X and Y-directions and across the bed using the carriage. These movements can either be done using the handwheel or can even be automated.
Carriage
Carriage is also called the cross-slide and is present between the tool post and the saddle.
Cross-slide can move across the machine perpendicular to the movement of the saddle.
Types of turret lathe
Depending upon the orientation, operation, and number of turrets, there are six types of turret lathes.
Horizontal Turret Lathe (Manual)
This is the oldest and most common type of turret lathe.
Horizontal Turret lathe, as the name suggests, has a turret aligned in a horizontal orientation.
The axis of the turret is co-linear with the axis of the workpiece.
Vertical turret lathe
In a vertical turret lathe, the axis of the turret head is perpendicular to the base of the machine.
The turret head can move up/down and side to side along the guideways.
Apart from the vertically oriented turret, it consists of two square tool posts on the sides which can hold 4 tools each.
The tool posts can also be moved in the X and Y directions to perform the machining operation on the workpiece.
Therefore, in total, a vertical turret lathe can house 14 different tools to work on the material.
This type of Turret lathe is suitable for working on large and heavy workpieces.
automatic turret lathe
Automatic Turret lathe is a modification of the manual Turret lathe.
This type of turret provides the ability to automate the sliding and indexing of the turret using a camshaft, thereby enhancing productivity by reducing machining time.
This reduces the need for a skilled operator to control the machine.
The automation of the process enhances repeatability, making automatic turret lathes ideal for mass production.
However, the automation of sliding and indexing with the help of a camshaft is suitable for simple geometries and does not facilitate the production of complex geometries.
CNC turret lathe
CNC stands for Computer Numerical Control. CNC Turret lathes use a computer-generated G-code to control the feed rate, speed of the spindle, and motion of the turret.
Computer Numerical Control (CNC) machines use a computer program to control various machining parameters.
These machines consist of a computer system that converts a digital design into special code (G-codes).
The G-codes are then interpreted by the controller to guide the CNC turret lathe to execute the desired machining process.
These machines also support automatic changing of the tools on the turret, thereby eliminating the need for human interference during the execution of the machining operation.
The computer-controlled motion of the cutting tool makes CNC turret lathes ideal for machining complex shapes with high precision.
Twin turret lathe
A Twin-Turret lathe consists of two automated turrets that can simultaneously perform machining operations on the workpiece.
This significantly reduces the cycle time to almost half the time taken to perform a similar machining operation on a single turret lathe.
Of the two turrets, one turret leads the other turret. This sequential operation between the two turrets allows the machine to perform roughing and finishing operations in a single pass.
You can load and unload parts from one spindle without interfering the operation of the other. Some Twin-Turret lathes can even run two separate programs on each of their spindles.
The setup of a twin-turret lathe takes longer than a single-turret lathe. Hence, twin-turret lathes are suitable for batch production, where a high volume of similar products is produced in a single sitting.
Haas Automation and CMZ are globally recognized for manufacturing twin-turret lathes and other premium CNC machines.
Comparing Turret lathe with other lathes
Turret lathe is a type of metal lathe that provides flexibility to mount multiple cutting tools on its hexagonal turret.
When compared to wood lathes, metal lathes offer more torque to rotate the heavy workpiece and deliver a strong cutting force for material removal.
Even the best wood lathes available on market offer comparatively less torque output, and therefore wood lathes are not ideal for machining metals.
Therefore, machining metal requires special metal lathes, and depending upon their features, structure, and material capabilities, metal lathes are of different types.
In this section, we will compare turret lathes with other similar metal lathes: Capstan and Engine lathes.
Turret lathe vs capstan lathe
In the table below, I have summarized the basic differences between Capstan and Turret lathe.
| Parameters | Capstan lathe | Turret lathe |
|---|---|---|
| Turret shape | Hexagonal, Square, or circular | Hexagonal |
| Speed of operation | Fast | Slow |
| Types | Horizontal only | Horizontal and vertical |
| Turret mounted on | Ram, which is mounted on saddle | Directly on saddle |
| Workpiece size | Small (up to 60mm in diameter) | Large (up to 120mm in diameter) |
| Workholding | Collet | Jaw chuck |
| Feed motion | Ram is moved | Saddle is moved |
| Size of machine | Lightweight | Heavyweight |
Summary of basic differences between Capstan and Turret lathe
Capstan lathe is a lightweight machine built to handle small workpieces of up to 60 mm in diameter.
Turret lathes, on the other hand, are larger and can handle workpieces that are almost double in size than what Capstan lathes can work on.
The non-rigid construction and the light weight of Capstan lathes make them unsuitable for performing heavy cuts on a workpiece.
Turret lathe, being heavier and more stable, can perform heavy cuts with relative ease.
The smaller workpiece handling capability of a Capstan lathe is also what makes them faster than a Turret lathe.
In Capstan lathes, the ram slides over the saddle to provide feed to the tool. This reduces the range of motion, thereby reducing the maximum length of the stock that can be machined.
In Turret lathes, the whole saddle can slide over the guideways, which provides a larger range of motion, allowing turret lathes to work on longer workpieces.
Some turret lathes allow the lateral movement of the turret head with respect to the bed, but the ram of capstan lathes do not provide the feasibility for lateral movement.
Indexing mechanisms on both the lathes are quite different. On Capstan lathes the handwheel of the ram is rotated in the reverse direction to index the tool.
Whereas in turret lathes, the turret has to be rotated manually after releasing all the clamps in order to index the tools.
Turret lathe vs engine lathe
In the table below, I have summarized the basic differences between Turret lathe and Engine lathe.
| Parameters | Turret lathe | Engine lathe |
|---|---|---|
| Speed | Faster | Slower |
| Size | Comparatively small | Large |
| Direction of rotation | Clockwise and anti-clockwise | Anti-clockwise only |
| Lead screw | Absent | Present |
| Number of tools contained | Up to six | Only one at a time |
| Price | Cheaper | Costlier |
Summary of basic differences between Turret lathe and Engine lathe
The primary difference between these lathes is the number of cutting tools that they can hold.
Engine lathes generally have a tool post that can house a maximum of 4 cutting tools, whereas the turret can house six cutting tools at a time.
Turret lathes take more time to set up, but they provide a faster machining rate, which makes them suitable for mass production.
On the other hand, Engine lathes need less time to set up, but their slow machining speed makes them unsuitable for mass production.
Turret lathes provide comparatively greater flexibility in adjusting the optimal spindle speed, allowing them to perform various machining operations on different materials.
Apart from these lathes, metal lathes are also available as Swiss lathes, CNC lathes, etc.
Benefits of turret lathe
Turret lathe has an obvious advantage over conventional lathes because they can accommodate up to six tools.
Changing tools in a conventional lathe machine takes time and makes the manufacturing process slower.
In a Turret lathe, the turret can be rotated to change the tools to work on the part. This saves time and reduces the need for skilled laborers.
Using turret lathes increases productivity by reducing tool change time, thereby reducing cycle time.
Automatic Turret lathes can manufacture duplicate parts with high repeated accuracy compared to manual Turret lathes.
Frequently asked questions
What is turret in a Turret lathe?
Turret in a Turret lathe is a gun-like tool holder that holds six tools that can be used interchangeably. The turret can be rotated about the vertical axis either manually by a handwheel or automatically by an automated mechanism.
Why is Turret lathe better than conventional lathe machines?
Turret lathes are better than conventional lathe machines because they hold multiple tools at the same time. The turret can be rotated to access the cutting tool required for the machining operation. This reduces tool-change time, thereby speeding up the manufacturing process.
What type of motor is used to control the turret of a Turret lathe machine?
Stepper or servo motors are used to control the turret of a Turret lathe machine. They offer high-precision in terms of RPM and angle of rotation which is required to align the tools exactly with the workpiece.
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