Mills and lathes are extremely popular tools in the manufacturing industry due to their capability to machine different kinds of metals and non-metals with high precision and repeatability.
While both do subtractive machining to produce the required part, there are significant differences in their design, operation, and capabilities.
The difference between lathes and milling lies in their operations. While lathes have a rotating workpiece, milling involves a rotating tool that removes the material from the workpiece. Furthermore, lathes have a horizontal configuration, while a vertical configuration is preferable for milling.
In this article, I have laid down the differences between lathes and milling based on several parameters.
In the end, I've also discussed their applications to help you understand which machine might be suitable for your application.
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A conventional manual lathe machine consists of parts such as a bed, head stock, tail stock, carriage, and feed mechanism.
Parts of a Lathe (Source: Kingston lathes)It consists of a high-speed rotating workpiece clamped in a mounting device such as a jaw chuck, magnetic chuck, or collet, and a cutting tool that moves along the X and Z axes of the lathe to produce the desired cut.
The bed is a single piece of cast iron on which all the other components are mounted. The carriage of the lathe machine slides over the bed.
The left end of the bed houses the headstock which comprises the drive system and controls. The drive system consists of a motor and a gearbox, which facilitates variable RPM for machining different materials.
Apart from that, the headstock also houses a mounting device, such as a 3-jaw or a 4-jaw chuck, in which the workpiece can be fixed for turning applications.
The tools on a lathe are mounted on the tool post, which has a unique design depending upon the type of lathes, such as turret lathe and gang tool lathe.
On the other hand, a conventional milling machine, such as a Bridgeport mill, consists of a worktable on which the workpiece is clamped for machining.
Parts of a regular Bridgeport MillThe worktable can move along the X and Y axes, while the high-speed rotating tool can move up and down along the Z-axis.
In manual and semi-automatic milling machines, the operator can rotate the handwheels to position the workpiece or the cutting tool appropriately.
The parts of a CNC milling machine are similar to a manual mill, except for the addition of a controller system and drive motors.
In CNC milling machines, the workpiece and the tool are positioned automatically according to the toolpath set by the CNC machinist and uploaded onto the machine.
A milling machine is vertically oriented, whereas a lathe machine is horizontally oriented. As a result, milling machines have a lower footprint than lathe machines.
The main difference between a lathe and a mill is the relative rotation of the workpiece and the cutting tool.
In a milling machine, the workpiece is clamped on the workbench and the cutting tool, which can move up and down, rotates to remove material from the surface.
The clamped workpiece can move along the X and Y axes to get the desired cut.
CNC routers can also be used for milling soft materials, but instead of a moving workbed, these machines consist of a cutting tool that can move along the X, Y, and Z axes.
On the other hand, a lathe machine has a rotating workpiece that is clamped in a holding device such as a chuck or collet while the cutting tool, mounted on the tool post, moves along the X and Z axes to make the desired cut.
Lathes, such as Turret and Capstan lathes, have a toolpost that can hold six tools at once and can be easily indexed to use different tools during the machining process.
Lathe machines primarily use single-point cutting tools to turn, chamfer, thread, groove, face, and bore a workpiece.
Lathe Cutting toolsTurning tools are used to remove material from the outer surface of a cylindrical workpiece.
Chamfering tools are used to chamfer the edges at an angle, whereas a boring bar is used to enlarge an already drilled hole.
A single lathe can be used for turning, boring, and knurling operations on various sizes of workpeices.
On the other hand, milling tools are multi-point cutting tools such as end mills, router bits, face mills, ball cutters, fly cutters, thread mills, and slab mills.
End millsEnd mills and face mills are similar except that in an end mill, both the ends and sides are utilized, whereas a face mill is designed to machine a surface only from the end.
Fly cutters also function like face mills, but they are used to achieve higher precision than face mills.
Slab mills are more commonly used in manual milling machines to machine large surfaces quickly. Hence they are also called surface mills.
Thread mills, as the name suggests, are used to create internal or external threads on a workpiece, also known as thread milling.
Due to the differences in the construction of the two machines, their machining operations are different from one another.
The most common operations of a milling machine are drilling, boring, and facing.
Drilling is performed to make a hole in a part, and a boring operation is performed to enlarge that hole larger with high precision.
Solid parts with uneven surfaces can be faced with a milling machine to provide a smooth, uniform surface for further machining operations.
Due to the vertical orientation of a milling machine, they can be used to cut gear profiles with high precision and repeatability, which is not possible using a lathe machine.
Lathe machines have a horizontal orientation that allows the workpieces to be threaded, turned, faced, and drilled.
Threading is one of the operations exclusive to a lathe machine. In this, the billet is machined by a sharp tool to cut threads on the outer or inner surface of the workpiece.
Lathe machines provide the ability to cut different types of threads such as screw threads, acme threads, taper threads, etc.
Drilling and facing are common operations that can be done by a milling machine also, although the orientation of the work axis is different in both machines.
Lathe machines are best suited for turning cylindrical workpieces with high accuracy. This is used to condition non-uniform billets for further machining operations.
Both lathe and milling machines can work on different types of metals and non-metals (mainly wood), but the shape of the workpieces differ.
Milling machines require the workpieces to be a block or roughcast.
When milling an upright cylindrical workpiece, it must be ensured that the workpiece is clamped firmly and has a small length-to-diameter ratio to avoid buckling of the workpiece under the cutting force.
Lathe machines work on billets or workpieces with a higher length-to-diameter ratio.
Workpieces used in a lathe machine are machined along the axis and the tailstock of the lathe provides the required counter support to hold long workpieces firmly.
A lathe is a machine that is generally used for the machining of axisymmetrical workpieces.
It is a horizontal machining center, where the workpiece rotates at high speed and the cutting tool moves around to make the desired cut.
Lathe machines are available in different sizes, such as benchtop, mini, midi, and full-size lathes.
Apart from that, lathe machines are also specified based on the material they can work on, i.e., wood lathes and metal lathes.
While wood lathes use a hand-held cutting tool, metal lathes consist of a tool post and are readily available as manual and CNC variants.
Lathe machines are majorly used for working on cylindrical workpieces. They can be turned, threaded, faced, and drilled.
These operations are useful in creating parts that can be used as tools, screws, furniture stands, cylindrical machining parts, etc.
Hard materials are usually turned with a special tool type called PCNB (polycrystalline cubic boron nitride) tools.
These tools don’t undergo extensive wear and tear as other tool types when used for machining hard materials.
However, machining hard metals require a constant flow of lathe coolant to minimize heat generation.
Milling is the process of using a high-speed rotating tool to remove material from a workpiece held stationary on the worktable. Milling machines are vertical machining centers and have a lower footprint than lathe machines.
Unlike lathe machines, milling machines can be used for machining different shapes and provides the flexibility to easily clamp the workpiece in different orientations on the worktable.
The rotating cutting tool in milling machines makes it easier to adjust the position of the cutting tool. This makes milling machines more versatile than lathe machines.
The rotating cutting tool of milling machines makes it ideal for flat profiles, which is not very suitable for a lathe machine.
Milling machines are suitable for machining gears with great precision, which is not possible in a lathe machine.
They are also useful in smoothening out uneven surfaces for further machining operations on that workpiece.
Other than that, milling machines can create grooves, bores, internal threading, and chamfers very effectively.
Lathe and milling machines differ from each other in many aspects, primarily in the orientation of the work axis and the type of workpieces they can process.
Lathe machines are horizontally oriented, hence they tend to take up a lot of space, whereas milling machines are vertically oriented which makes them more compact.
Although both machines are versatile in terms of machining capabilities, milling machines can work of workpieces of almost any shape, providing a broader application.
However, lathe machines are one of the most widely used machines for DIY and industrial operations due to the specific machining operations they can perform, which is not possible with a milling machine.
The main difference between a CNC mill and a CNC lathe is the relative movement of the workpiece and the tool. Although both CNC mill and CNC lathe are automated machines with the help of G-code, in a CNC mill the tool rotates and the workpiece is fixed, whereas in a CNC lathe, the workpiece rotates and the tool is stationary.
The similarities between a milling machine and a lathe machine are that both of them are subtractive manufacturing machines, meaning that they remove material from a workpiece to achieve the desired shape and features. Additionally, both machines can make grooves, drill holes, chamfer, and face workpieces.
The difference between a horizontal and a vertical machining center is the direction of the tool axis. In a horizontal machining center, the tool machines the workpiece parallel to the work bed, whereas in a vertical machining center the tool operates perpendicular to the workpiece.
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