cnc machine cutting material

Horizontal vs Vertical Milling: The Differences Explained

In the modern metal fabrication industry, milling is a popular process that offers skilled tradespeople a way of shaping and cutting materials expertly. It’s used to produce some of the most common and vital products we use every day. In this article, we’ll look at horizontal milling machines and vertical milling machines, comparing the two types and understanding their differences and uses. 

Comparing Horizontal and Vertical Mills

Milling is the process where the material is removed from a workpiece with the aid of a rotary cutter. A standard milling machine consists of a rotating spindle that is powered by a motor. The spindle is capable of movement along one or two axes and often has variable speed settings. The spindle is mounted above a worktable, where the workpiece to be cut is mounted with vises, blocks, or chucks. Depending on the type of mill, the worktable may be equipped with a power feed.

Most milling machines fall into one of two categories depending on the orientation of the rotating spindle. Vertical and horizontal milling machines both perform roughly the same operations, but the production process is different. Both types have advantages and disadvantages, and both are better suited to particular operations.

Here is an overview of horizontal vs vertical mills.

What Is a Vertical Milling Machine?

vertical milling machine is the most commonly used type and features a vertically oriented cutting head or spindle. The spindle holds a rotating cutting tool against the workpiece. The spindle moves vertically, along the Y-axis. Other machine parts shift along the X-axis or even the Z-axis to position the workpiece correctly.

Vertical mills are ideal for projects worked on a single side; this includes sectioning operations or finishing operations like end millwork. Vertical mills themselves can be further divided into two vertical milling machine types: bed milling machines and turret milling machines. Each functions a little differently from the other, and each offers unique advantages.

Turret Mill: The mill of choice for many small machine shops, turret mills feature a fixed spindle. To achieve different cuts, the bed of the mill moves both horizontally and perpendicularly. A turret mill is very versatile, given how it can manipulate the material’s position in both directions. Turret mills are often made as CNC mills, which increased their use and function to an even larger degree. Since mills benchtop moves, it requires a more complicated construction, making turret mills best suited for smaller projects.

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Bed Mill: A bed mill, on the other hand, moves the material perpendicular to the axis. The bed of the mill moves along the Y and Z axes and the spindle moves along the X-axis, providing a full, 3-axis range of movement. The spindle movement, coupled together with the horizontal movement of the table enables milling of a variety of depths and shapes. This mill is excellent for projects that need large, heavy pieces compared to turret mills.

The Best Features of Vertical Milling Machines

The CNC Supra Vertical Knee Milling Machine, available in both 9×49 and 10×54

i). Popularity: Vertical mills – often referred to as knee mills – make up most of the milling machinery in the country. In the metalworking industry,

vertical mills don’t typically require the extensive investment that heavier, more expensive mills do. Because of the low upfront cost, production costs for parts made on knee mills are also lower. And because these are the mills most commonly found in machine shops around the country, skilled operators are easier to find.

ii). Ease of Operation: The structural design of vertical mills gives operators better visibility while working. This gives the operator a higher chance of spotting and correcting potential problems. Depending on the model, digital readouts and CNC controls make tracking the position of the workpiece even easier. For CNC mills, programming is made easy through commonly-used G-code.

iii). Production Flexibility: Due to their versatility, integration with CNC, and variety of possible tooling, vertical mills are perfect for small-scale production projects or even one-off parts. Prototyping, custom jobs, or special-order product lines requiring high precision are ideal for vertical mills and are often the exact type of job likely to be sent to a local machine shop rather than a large industrial facility.

What Is a Horizontal Milling Machine?

Like vertical mills, horizontal milling machines feature a rotating spindle. This spindle is mounted horizontally above the bed. The cutting tool, often a disc resembling a saw blade or a grinder, can move along the length of the spindle. This allows the horizontal mill to remove material along the length of a workpiece, or even functioning as a planer, finishing the entire surface. When coupled with a rotary table, the horizontal mill is nearly as versatile as a vertical mill.

Compared to vertical milling machines, horizontal mills are capable of performing heavier and deeper cuts.  Typically horizontal mills have heavier horsepower motors and often larger beds, making them ideal for heavy-duty settings. Many manufacturing companies apply them to cut slots or grooves, such as t-slots, into workpieces. They can also do milling operations while positioned at different angles.


The Best Features of Horizontal Milling Machines

i). Chip Evacuation: Due to the horizontal mills’ layout, gravity aids in pulling the chips out during cutting. Better chip evacuation results in cleaner surface finishes and less overall work required.

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ii). Solid Construction: Horizontal mills are found most often in heavy industrial settings for large production runs. Most are built accordingly, with a rigid construction that translates to the machine vibrating less, deflecting less, and functioning more smoothly than vertical mills

iii). Productivity: Integrated pallet changers, variable spindle speeds, and heavy-duty jigs make many horizontal mills perfect for large quantities and complex workloads. Vertical machining centers offer more flexibility, but horizontal mills provide stability, durability, and power.


What Are Milling Machines Used For?

Milling machines are versatile devices. They come in varying sizes ranging from small ones used in homes or garages to larger ones needing warehouse space to function. At their core, milling machines use a selection of tools to carve and drill into raw materials to make shapes and nearly finished products. They can add threads for bolts, drill holes or create precise shapes from any material.

Cutting Tools

Different tools are used depending on the cuts required and the material involved. Cutting tools are held in the collet at the end of the spindle. While rotating, the head is brought into contact with the material being milled.

Taps are used to cut threads. When a tap has been used on a hole, you thread a bolt into it. A mill will be used for cutting the material through and around the workpiece. Various types and sizes are used for varying purposes.

Machining Parts

To program the computer or make parts, a machinist will follow a blueprint. By choosing the correct tools and following the right sequence of operations, a machinist can transform raw material into a precise part within acceptable tolerances.

Precise Computer Numerical Control

A computer numerically controlled mill can make concise production parts with little operator involvement. Special motors and precise measuring tools called stepping motors choose tools, move the table and head, and machine the parts to exact dimensions that are either difficult or time-consuming to perform manually.

Machinists train in G-code programming to program the right sequence for CNC machines. Even operators without advanced programming knowledge can often use CAD programs and conversational programming tools to create the correct programs.

Popular Products Made With Milling Machines

Without a doubt, you use products made and formed by milling machines every day. Here are some of the most common and unknown products made by milling machines.

Pens and Pencils. Ever been in class, taking notes, or signing a document at the office, and wondered where the writing utensil you are using came from? A milling machine is needed to make the parts of a machine that will produce your pencils or make the molds that will produce your pens.

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Guitars. The operating system of a CNC machine is ideal for creating the exact cuts, which gives the instrument its attributes and unique looks. For the wooden clock to function properly, numerous separate and tiny parts are required to be cut precisely. And milling machines cut these clock parts.

Police Badges. The design of the badge will be inputted in the CNC milling machine operating system, which will then make unique small cuts representing the police emblem.

Surgical Tools. From scalpels to stretchers and advanced imaging equipment, milling machines produce intricate parts for the medical community.

Choosing between Vertical and Horizontal

Both types of milling machines have their merits. The choice between the two depends entirely on the kind of milling that needs to be done. The number of planes on which a piece needs to be worked, as well as the shape and size of the piece, are major factors in deciding whether the milling is more suited to vertical or horizontal processes. Heavier items and those that need to be worked on multiple sides lend themselves more readily to horizontal milling, while work such as sinking dies is best suited for a vertical milling machine. Many items, however, can be worked on either type of milling machine by using the correct techniques.

Both vertical and horizontal milling machines can make use of CNC (computer numerical controlled) technology to automate milling for fine control, especially on complex milling jobs or when exact repetition is needed. There are also various types of add-on parts and cutting heads that can be used to modify a horizontal mill to do vertical milling or vice versa. This is a great advantage to a small shop that usually needs one type of mill because it allows a wider range of milling on a single machine, especially for applications that are not often needed.

If you’re not sure which process you need, vertical mills are often the most flexible and offer the best value. Even a simple benchtop CNC vertical mill can perform complicated and intricate cuts, adding immense value to any workshop.

About Peter Jacobs

Peter Jacobs is the Senior Director of Marketing at CNC Masters, a leading supplier of CNC mills, milling machines, and CNC lathes. He is actively involved in manufacturing processes and regularly contributes his insights for various blogs in CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general. You can connect with him on his LinkedIn.

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