Lathe machines are used for the manufacturing of axisymmetric parts through operations such as turning, facing, threading, boring, etc.
Depending upon the type of material it can machine, lathes are generally categorized as metal lathes and wood lathes.
A wood lathe is specifically used for woodworking, whereas a metal lathe is ideal for metal turning.
But what makes them different? Why can't you use the same lathe for machining both materials? And how do you differentiate between a metal lathe and a wood lathe?
This article will answer the above questions by exploring the differences between wood lathes and metal lathes.
Difference Between Wood Lathe and Metal Lathe
The difference between wood lathes and metal lathes lies in their material capability and tool holding configuration. Wood lathes are high-speed lathes that use a hand-held tool for shaping the workpiece, whereas metal lathes are high-power lathes with the tool mounted on the tool post, moved around by hand wheels.
Although both lathes perform similar operations, there are various factors that set a wood lathe apart from a metal lathe.
|Parameters||Wood Lathe||Metal Lathe|
|Size||Comparatively Smaller||Comparatively Large|
|Torque/Speed||Low Torque/High Speed||High Torque/Low Speed|
|Tool Holding||Held by hand over tool rest||Mounted on a tool post|
|Accuracy||Comparatively lower||Comparatively higher|
|Cost||Low cost||High cost|
|Automation||Hand-held tool cannot be automated||Can be automated|
Key differences between wood lathe and metal lathe
Build and Design Differences
A typical metal lathe consists of a workpiece mounted on a high-speed rotating spindle and a movable tool post housing the cutting tool.
The tool post consists of a cross slide that allows the lateral movement of the cutting tool in X-direction, and the carriage, along with the tool post, moves in the Z-direction.
These XZ plane movements of the tool are manually controlled with the help of hand wheels.
Furthermore, these movements can be automated by using a servo motor that drives a lead screw to provide a uniform feed to the cutting tool.
Depending upon their construction, application, and processing methods, different types of metal lathes, such as Engine lathes, turret lathes, swiss lathes, capstan lathes, etc., are available on the market.
On the other hand, a wood lathe consists of a hand-held tool positioned on a tool rest.
The tool is guided by hand to plunge into the surface of the workpiece and remove the material, producing the desired shape.
This eliminates the need for various tool holding and guiding parts such as tool post, cross rail, carriage, hand wheels, lead screw, etc., thereby reducing the size of the machine.
Apart from this, both the lathes consist of a headstock, tailstock, bed, spindle, chuck, and spindle motor.
Generally, wood lathes are small, benchtop lathes that can fit a regular workshop bench, whereas metal lathes are bulky, center lathes that occupy a large workshop space.
Therefore, wood lathes offer better portability than metal lathes, which are basically stationary workstations that cannot be moved around easily.
Speed and Torque
The machining ability of a lathe is determined by its spindle speed and torque.
A lathe machine with higher torque is ideal for machining hard materials as it provides the power to cut through the hard material without halting the spinning action of the spindle.
On the other hand, a lathe with a higher speed is ideal for machining soft materials where less power is required to cut through the material.
Hence, wood lathes are also known as speed lathes.
High speed facilitates the production of a clean cut with a high surface finish.
Generally, the best wood lathes are high-speed (1200–3600 RPM) lathes with less torque, whereas metal lathes have high torque with comparatively less spindle speed (500–1500 RPM).
Mode of Operation
The mode of operation is similar in both, wood and metal lathes, where the workpiece is mounted on the headstock, and the tailstock provides support for longer workpieces.
High speed rotating spindle spins the workpiece and a stationary tool carves the desired shape.
However, the major difference between the operation of both the lathes lies in the movement of the tool.
In metal lathes, the hand wheels consist of measuring scale markings that can be used to provide precise feed and depth of cut to the cutting tool.
Whereas in wood lathes, the cutting tool is manipulated by hand and the accuracy of the machining operation is solely dependent on the skill and experience of the machinist.
A hand-held tool can be moved simultaneously along the X and Z-axis with just a deflection of the hand.
Whereas controlling the tool post of a metal lathe along the X and Z-axis requires simultaneous operation of both the handwheels, which can be difficult to perform manually.
Metal lathes provide the ability to automate the feed of the cutting tool, using a camshaft arrangement, which cannot be done on wood lathes.
These metal lathes can further be enhanced by integrating them with a computer system and turning them into CNC machines.
The ability to provide precise feed and depth of cut by using the hand wheels makes metal lathes more accurate than wood lathes.
Metal lathes are used for producing metal workpieces with a tight tolerance that are used in various industries like automobile, sheet metal, etc.
Furthermore, the ability to automate the process by using a CNC machine system further enhances the accuracy of a metal lathe.
The hand-held tool, on the other hand, provides comparatively less accuracy but high flexibility to machine versatile shapes and contours.
Generally, wooden parts have a comparatively higher fit-tolerance than metals, and therefore the less accuracy of wooden lathes does not have any significant effect on the machining operation.
However, it is strongly recommended to have a highly-skilled operator to produce the best results on a wood lathe.
Generally, metal lathes are larger, heavier, and more powerful than wood lathes, and therefore are comparatively more costly.
A typical metal lathe (engine lathe) can cost around $4000-$12000 and can go further up for a multi-axis CNC metal lathe.
Wood lathes are smaller in size and a typical benchtop wood lathe generally costs around $500-$2000 and can go higher depending upon the size and power of the lathe.
Apart from the initial cost of the machine, there are various operational costs involved with a lathe.
Lathes can be used for performing different machining operations on different materials, and each operation requires a specific cutting tool.
There are various lathe cutting tools that can be selected on the operation to be performed and the type of material to be machined.
Machining of metals requires special hardened tools that are comparatively more costly than regular tools used for woodworking on a wood lathe.
Furthermore, machining of metals generates heat which can damage the workpiece and the cutting tool.
Therefore a cooling system is required for regulating the temperature and preventing the workpiece from overheating.
This further increases the overall cost associated with metal lathes making them comparatively more costly than wood lathes.
A wood lathe is used for performing various woodworking operations like carving, sanding, polishing, shaping, etc.
The hand-held tool provides the flexibility to easily carve smooth contours with variable cross-sections which can otherwise be difficult to machine on a manual metal lathe.
Wood lathes are used for carving various wooden applications such as furniture legs, vases, lamp posts, candle holders, baseball bats, wooden bowls, and other axisymmetric applications.
These lathes can be used for machining of all types of wood, but their low torque is not suitable for machining hard materials like metals.
Furthermore, machining of metal workpieces requires high cutting force which cannot be delivered effectively by a hand-held tool.
Metal lathes are used for machining metals to produce an axisymmetric part with the desired shape.
These lathes offer better control and can be used for performing various operations like turning, taper turning, knurling, threading, chamfering, boring, drilling, etc.
Metal lathes are generally used for machining common industrial metals like aluminum, steel, copper, brass, etc.
Unlike wood lathes, metal lathes can also be used for machining other materials like plastics and wood.
However, the quality of wood products produced on a wood lathe is far superior to that of a wooden part machined on a metal lathe.
As a result, metal lathes are not generally used by professionals for woodworking.
Woodworking on Metal Lathe- Is it Possible?
Metal lathes are versatile machines that provide flexible speed and power configurations for roughing and finishing operations.
A roughing operation provides greater torque to facilitate maximum material removal, whereas a finishing operation provides faster speed to produce a high surface finish with minimum material removal.
This variable speed makes them ideal for working on different materials, including wood.
That gives rise to the question of why not purchase an all-rounder metal lathe instead of a wood lathe?
The answer to this question depends upon factors such as quality, cost, and flexibility of woodworking.
A wood lathe is specially designed for working on wood and therefore produces extremely smooth wood products with a high surface finish.
Although a metal lathe can be used for machining wood, the comparatively low spindle speed results in a poor surface finish.
Woodworking on a lathe is performed by maintaining a shallow depth of cut at high speed. Using a low-speed lathe and digging into the wooden workpiece can result in cracks along the grain of the wood.
Furthermore, the tools used for wood turning cannot be readily mounted on a tool post, and using an alternative metal tool will affect the quality and might result in overheating of the workpiece, leading to burns.
Therefore, a metal lathe can be used for woodworking but at the cost of the machining quality.
Similarly, can a wood lathe be used for metal?
The answer is yes, it can be used for machining soft metals but at the cost of quality and accuracy.
Apart from the quality of woodworking output, the cost of the machine also plays an important role in opting for a wood lathe.
Wood lathes are smaller, occupy less space, and are comparatively cheaper than metal lathes.
These lathes are budget-friendly and can be used for a variety of woodworking applications.
Therefore, for professional woodworkers and for hobbyists who are primarily focused on woodworking projects, a wood lathe is a logical option that serves the purpose in budget.
A metal lathe provides precision in tool movements, but a wood lathe provides flexibility.
Generally, woodworking is used for making artwork, furniture, and other decorative items, that require a skillful operator with creative ideas.
A hand-held tool provides better flexibility in shaping the idea into a craft by gliding the tool freely along the XZ plane.
Whereas, a metal lathe cannot provide the same level of flexibility in tool movements unless using a very expensive CNC metal lathe.
Characteristics of a Wood Lathe
A wood lathe is a benchtop lathe with a simple operation in which a spindle motor spins the workpiece at high RPM and a hand-held tool removes the material.
In wood lathes, the tool post is replaced by a tool rest mounted on the bed and consists of parts such as banjo, banjo lock, and tool rest lock.
The banjo consists of an O-shaped or a rectangular clamp bolt underneath, that slides into the guide rail on the bed, providing flexibility to move the tool rest along Z-axis.
After placing the tool rest along Z-axis, you can use the banjo lock to tighten the clamp bolt and hold the tool rest securely in place.
The tool rest lock is used to adjust the height and orientation of the tool rest, and tightening the tool rest lock holds it firmly in the desired orientation.
Apart from mini and midi formats, wood lathes are also available as full-size lathes that do not require a bench to support them.
Wood lathes generally have a low power–high spindle speed configuration and use a belt-drive transmission to power the spindle.
The low power of wood lathes makes them beginner-friendly, but careless use of the hand tool at high RPM can result in severe injuries to the operator.
Characteristics of a Metal Lathe
Metal lathes are generally full-size lathes that consist of a headstock, tailstock, bed, tool post, carriage, lead screw, feed rod, traversing wheels, legs, etc.
These lathes are also available in the bench lathe format, such as Proxxon PD 400, ideal for working on small-size metal workpieces.
Unlike wood lathes, the cutting tool of a metal lathe is mounted on the tool post and moved around by moving the traversing wheels.
The tool post of a metal lathe can be of four types: Single screw, Open side, Four bolt, and Four way toolpost.
Single screw toolpost, as the name suggests, consists of one screw that clamps the cutting tool in place.
This type of tool post is not recommended for applications where a strong cutting force is to be delivered.
Open side tool post is one of the most commonly used tool posts that consists of two or more bolts holding the cutting tool in place to ensure firm clamping for delivering a strong cutting force.
Four bolt tool posts can hold two cutting tools, with two bolts for clamping each tool.
Four way tool post is accessible from all four sides and can hold a total of four tools, one on each side.
Having multiple tools mounted on the tool post increases the productivity of the process by reducing the tool change time.
Metal cutting requires high torque, and therefore metal lathes have high power and low-speed configuration.
Generally, metal lathes use a belt drive or direct drive system to power the spindle.
Direct drive provides higher power output and quick speed variation, making it ideal for high-precision industrial lathes.
Metal lathes are comparatively more complex and pose a higher risk of injuries than wood lathes, therefore requiring an experienced machinist to operate.
Wood lathes are comparatively smaller and less powerful and are ideal for working with soft materials.
Metal lathes are generally bulky machines drawing high power, suitable for working on hard materials.
While metal lathes provide better tool control for precision carving, wood lathes provide greater flexibility to carve complex shapes with smooth contours.
The high power and variable speed of metal lathes enable them to be used for machining of metals, plastics, and even wood.
Although wood lathes provide variable speed control, it is not recommended to use them for machining metals due to various design and performance limitations such as low torque, hand-held tools, less rigidity, etc.
Overall, both the machines excel in their individual applications, but the versatility and availability of automatic CNC variants make metal lathes a better option for an all-purpose lathe.
Frequently Asked Questions (FAQ)
What are mini, midi, and full-size lathes?
Mini, midi, and full-size are the classification of wood lathes depending on their size and power.
Mini lathes are the smallest lathes that can handle workpieces with a maximum length and diameter of around 20" and 10", respectively. Where Midi lathes can handle a workpiece with a maximum length and diameter of around 20" and 12", respectively. But provides a higher power output of around 1HP.
Similarly, full-size lathes can handle workpieces having a length and diameter above 14" and 20", respectively. These lathes can have a spindle motor with a power rating ranging from 0.5HP to 5HP.
Are metal lathes available in bench lathe formats?
Yes, metal lathes are also available in bench lathe formats. These small lathes are generally used for machining small-size metal objects (watch-making) and performing other miscellaneous operations like grinding, sanding, etc.
Can we use a wood lathe for grinding metal?
Yes, a wood lathe can be used for grinding metal. However, it is not recommended to use them for metal operations where a high volume of material is to be removed.