10 KEY DIFFERENCES BETWEEN HORIZONTAL AND VERTICAL MILLS

10 KEY DIFFERENCES BETWEEN HORIZONTAL AND VERTICAL MILLS
In the modern metal fabrication industry, manual and CNC milling are essential operations that allow a skilled machinist to cut a workpiece and turn it into a high precision component or product. Whether you're using a manual or CNC milling machine, machine shops choose between two basic types of milling machines: vertical and horizontal.
In this guide, we will compare horizontal and vertical milling machines to better understand their differences and uses.
In both machines, material is removed from a workpiece using an end mill or other cutter fixed to the milling head. Unlike a metal lathe where the part rotates and the cutting tool is fixed, the milling machine has a rotating spindle for the cutting tool. At the same time, the workpiece is fixed to the workbench with a mounted vise or by clamping the workpiece directly to the workbench.
The spindle can move up and down along one or two axes on a vertical milling machine and often has variable, high speed settings. Depending on the mill type, the workbench can usually be equipped with a power feed for longitudinal feed and a digital readout (DRO) for accurate sizing. Many mills also have a cooling system.
Most milling machines fall into one of two categories, depending on the direction of the rotating spindle. Vertical and horizontal milling machines perform roughly the same operations, but the manufacturing process is different. Although each has its advantages, the vertical milling machine is the much more versatile of the two.
Here are ten key differences between horizontal milling machines and vertical milling machines and a brief explanation of each.
1. Spindle Orientation
As the name of each suggests, horizontal machining centers have a horizontal spindle that runs parallel to the surface of the workbench. The machine's cutting tool removes material from the workpiece as it rotates around this horizontal axis.
In vertical machining centers, a vertical head runs perpendicular to the surface of the workbench and the cutting tool rotates in a vertical spindle to remove material from the workpiece.
2. Team Geometry
The shape and characteristics of the milling tools and cutting tools are different for the two types of milling machines. Horizontal milling machines have shorter and thicker tools that can make deeper cuts and remove more material than vertical milling machines.
Vertical milling machines use long cylindrical tools, often called end mills, for more precise but shallower cuts in smaller workpieces.
3. Cut Properties and Accuracy
The geometry of the cutting tool directly affects the cutting characteristics and results. Because they are shorter and thicker, horizontal tools have the stability to support them during deep, heavy cuts. On the other hand, vertical tools cannot produce deeper cuts because they vibrate, affecting the accuracy of the cut and sometimes breaking.
4. Versatility
Vertical milling machines win the award for versatility. Machinists use them as boring mills, but they can quickly turn into a drill press which is an awkward operation on a horizontal mill. Both machines can butt and slot, but the vertical mill is more adept at prototyping, custom work and engraving.
5. Machine Cost
Vertical milling machines typically have lower initial cost, such as operating and maintenance expenses, than horizontal milling machines, making them the more popular choice between the two, especially among smaller shops. More machine operators are familiar with vertical machines, making them easier and less expensive to operate than horizontal models.
6. Material Removal Rate
Horizontal milling machines have a much higher metal removal rate than vertical mills because they are more stable and can make deeper cuts. Machinists typically choose vertical milling machines for operations such as facing and grooving because the cuts are not that deep and they are precise. However, this limited cutting potential results in a lower removal rate for vertical milling.
7. Overarm and Arbor Support
The horizontal milling machine has two elements that the vertical mill does not have: the upper arm and the spindle support. The upper arm is a horizontal beam at the top of the column. Depending on the type of machining needed, horizontal cutters can hold either a cutting tool or a spindle. If the spindle is used for a particular type of milling, it requires a spindle support to align and support the spindle. The arbor supports are fixed to the upper arm. Both of these parts are specific to the horizontal mill.
8. Number of Edges for Machining
Horizontal milling machines allow the operator to approach the workpiece from several angles and sides, while vertical milling machines operate in a single plane. Also, a horizontal mill is better suited for customizable jobs, as certain add-ons and features for horizontal installation are not available in a vertical mill..
9. Chip Evacuation
During machining, the metal chips produced tend to remain on the workpiece surface of the vertical mill, causing melting and defects that may require post-processing. Horizontal cutters throw chips away from the work table and towards the floor, leaving a better machined surface.
10. Finding Trained Operators
In addition to the high initial, operating and maintenance costs, another difference between the two types of mills is finding trained operators with experience and expertise in the horizontal milling machine. Because these machines are scarce, only a few machinists have hands-on experience with them.
What is Vertical Milling Machine?
You will see a vertical milling machine in almost every machine shop. As the name suggests, it has a vertically oriented cutting head or spindle. With the aid of a drawbar, the R8 spindle holds the rotating cutting tool used to machine the workpiece, and on some machines, a feather moves the spindle vertically along the Z axis. The machine moves up and down along the X-axis, Y-axis, and sometimes along the Z-axis, depending on the machine.
The vertical milling machine can function like a drill press if the stylus moves vertically on the Z-axis. These machines are ideal for projects where work is one-sided, including cutting operations or finishing operations such as chamfering. Vertical mills can also be divided into two types of vertical milling machines: knee mills (sometimes referred to as Bridgeport type machines or turret milling machines) and bed milling machines (commonly referred to as bed mills). Each functions differently from the other and each offers unique advantages.
Machinists may use different tools depending on the type of cut and the material involved. The cutting tools are held in the collet or directly on the milling head, and the milling head moves into the workpiece as the cutting tool rotates.
Drills and taps can also be used to create holes and internal threads. A variety of end mills and cutting tools are available for machining materials from aluminum to titanium.
Knee Milling: The machine tool of choice for many machine shops, knee mills have a fixed spindle. The knee moves vertically on the Z-axis and the table moves on a longitudinal X-axis and an input-output Y-axis. As mentioned earlier, the rotating shaft inside the pen provides another Z-axis.
Many CNC mills today are knee mills and their versatility has been developed as a standalone or benchtop model. Depending on table dimensions, a variable speed vertical mill has an almost endless amount of machining uses. Many knee grinders have an R8 spindle taper and are available in single phase for home shops and hobbyists; this is perfect for home machinists with a machine tool and a band saw for producing small parts.
Bed Mill: The table of the bed mill does not move up and down along the Z axis. Instead, vertical motion comes from the spindle. Unlike the knee mill, where the pencil moves but the motor does not, the entire head and motor of the bed mill move up and down on the Z axis. But just like the knee mill, the work table of the bed mill moves along the X-axis and Y-axis.
Sleeper cutters work well when large and heavy workpieces need to be machined.
What are Vertical Milling Machines Used for?
Due to their versatility, vertical milling machines are suitable for almost any industry. In fact, the vertical knee router is sometimes referred to as a "mill drill" because it can perform milling and drilling operations. Here are a few of the many components and products from vertical milling machines and the industries that use them:
• Shafts, gears, pins etc. It is an excellent choice for the manufacture of automotive parts, as it requires many vertical milling operations.
• The transportation industry relies on parts produced by the CNC vertical milling machine. Many of these components help keep their products and personnel safe during shipping.
• Agriculture depends on vertical CNC mills to make parts such as livestock gates and various farm equipment components.
• Vertical CNC milling machines can face, slot, drill and bore, making them invaluable in machines specific to the manufacturing industry and tooling used in many manufacturing processes.
• Perfect for prototyping, custom work or engraving
• With variable spindle speeds and other features, vertical CNC mills can complete simple and complex metalworking projects and can even be used as a router to machine large, flat plates in a variety of industries.
• They are so versatile that vocational schools and science labs purchase them as a valuable teaching tool for students to understand the grinding process..
What is Horizontal Milling Machine?
Like vertical mills, horizontal milling machines have a rotating spindle. However, this spindle is mounted horizontally. The cutting tools used in these machine tools are typically shorter and thicker, often similar to a grinding wheel, rather than the long, thin end mills you would see on a vertical milling machine.
While not as versatile as a CNC vertical knee router, horizontal cutters can make heavier and deeper cuts. The motors on these machines often have more horsepower to move larger bearings and heavy workpieces.
What are Horizontal Milling Machines Used for?
Horizontal milling machines are mainly used in the following machining operations:
• Machining grooves on a workpiece
• Machining slots
• Multi-sided face milling operations
• Machining jobs involving extremely heavy workpieces and difficult materials
• Horizontal milling machines are an excellent choice for certain complex projects such as the manufacture of scalpels and diagnostic imaging equipment for the medical industry.
• Drilling, tapping and boring in the horizontal plane.
Choosing between Portrait and Landscape
Both milling machines may have their advantages, but the vertical milling machine will always stand out in terms of overall versatility, reliability and affordability. Unless your company has special needs, such as handling large, bulky or heavy parts, the choice is clear. You can use the vertical milling machine for so much more: high-volume production work, repair work, tool and die, metal dies, engraving and the list goes on!
Adding Precision Computer Numerical Control (CNC) to a Vertical Milling Machine
A computer numerically controlled (CNC) mill can produce high quality parts with minimal operator intervention. Special motors and precision measuring tools, called stepper motors, select tools, move the table and head, and machine parts to precise and repeatable sizes. Many parts produced on machines such as the CNC Supra Vertical Knee Mill are too complex and time consuming to try on a manual mill.
A CNC machinist or programmer follows a drawing to machine parts on a machining center. By choosing the right tools and following the correct sequence of operations, a machinist can turn raw material into a precision part within acceptable tolerances.
Machinists trained in G-code programming create the appropriate sequence for CNC machines. Even operators without advanced programming knowledge can quickly become familiar with and comfortable with the user-friendly CAM software by tweaking the program or even creating some basic programs.