Drilling Machines - Parts, Types, and Uses

A drilling machine is a power tool that is used to create cylindrical holes in a workpiece. The tool bit is rotated at high speed and pressed into the workpiece to create a cylindrical hole that passes either partway (blind hole) or all the way through (through hole) the part. A drilling machine's speed is adjustable, and the feed rate into the workpiece can be either manually or automatically. Drilling machines can be mounted directly to a concrete floor, to a work table, or can even be portable. Figure 1 below is an example of an industrial drilling machine:

A drilling machine is a tool used for drilling holes in various materials, such as metal, ceramic wood, or plastic. It can be either portable or stationary. A drilling machine is very versatile and can be used to make a variety of hole types and geometries as listed below:

1. Drilling: The most common use of a drilling machine is making either blind or through holes in a workpiece.
2. Reaming: Used to finish an already-drilled hole, improving both its dimensional accuracy and its surface finish.
3. Countersinking: After a hole is drilled it may be necessary to create a countersink in the workpiece. A countersunk hole has a conical cutout to accommodate the head of a fastener that must be flush with or lower than the surface of a finished part.  
4. Tapping: Once a hole has been drilled, it may need to be threaded to accept a threaded fastener like a screw or bolt. A tap can be attached to the machine and used to cut internal threads.
5. Boring: A drilling machine can be used to increase the diameter of an existing hole through the process of boring. 
6. Counterboring: A counterboring tool is used to create a shallow, enlarged cylindrical cutout so that a fastener's head will fit flush with or below the work surface.

A drilling machine works by rapidly rotating a tool bit and lowering it into the desired area at a predefined tool speed and feed rate to create cylindrical holes in a workpiece. The workpiece must be securely held in place on the drill table during drilling operations using vises and clamps. Most drilling machines are oriented with the drill in the vertical position, however, some specialized drills are designed to drill horizontally. This orientation typically allows for the drilling of deep holes in long parts where a vertical arrangement would be impractical. If drilling in a different orientation is required the part will have to be re-position. The machine speed is adjustable for different cutting tools or materials being used.

A drilling machine has several key components that work in tandem to drill precise, consistent holes. The main parts of a drilling machine are listed below:

1. Base

The base of the drilling machine supports the machine and can either be fixed to a workshop floor or mounted to a work table in the case of smaller machines. Some bases have slots to allow for bolting and holding larger workpieces that cannot fit on the table.

2. Column

The column is usually a hollow, cylindrical structure that connects the base, table, and head of a drilling machine. The column also serves as a linear slide on which the table moves up and down. The table clamps onto the column once positioned as desired.

3. Arm

On larger drilling machines the arm is attached to the column and is used to support the spindle and drill chuck. The arm also allows for some travel in a direction perpendicular to the column. Smaller machines do not have an arm and instead, have the spindle positioned relatively close to the column on the head assembly.

4. Drill Head

The drill head contains the spindle, feed mechanism, and drill chuck. The spindle is usually driven by an electric motor via a gearbox. For larger machines with arms, the electric motor’s power can be transmitted via a series of V-belts and pulleys.

5. Worktable

The table provides a stable surface for the workpiece. It can be raised or lowered to adjust the drill bit's distance from the workpiece. The table also has T-slots or holes to facilitate clamping of the workpiece. A sensitive drill has a much smaller worktable when compared to a gang drill, for example. A sensitive drilling machine worktable is not designed for heavy loads whereas a gang drills worktable is. 

6. Feed Mechanism

The feed mechanism is designed to control the rate at which the drill is lowered into the material. The optimal feed rate and the speed of the drill bit are determined by the type of material being drilled and the size of the drill bit.

7. Spindle

The spindle is a shaft assembly with bearings that connects the electric motor to the chuck. Spindles are designed to have as little rotational eccentricity as possible to ensure drilled holes are concentric.

8. Chuck

The chuck is a mechanism used to grip the tool tightly enough to stop the tool from slipping during drilling operations. A drill chuck typically has three jaws whose position can be adjusted to account for different drill bit diameters. When adjusted, these jaws move either radially inwards or outwards to account for different diameters. 

9. Electric Motor

The electric motor drives the spindle either directly with a gearbox or with a series of belts and pulleys. The electric motor can either be mounted to the base of the machine or at the top of the column. Like the feed rate, the rotational speed can be adjusted for different drill bits and materials. Drills that allow for tapping also need to have very low minimum speeds on the electric motor. In this case, a VSD (Variable Speed Drive) is installed.

There are many different types of drilling machines, each of which is designed with a specific application in mind. Listed below are some of the most common types of drilling machines: 

1. CNC Drilling Machine

A CNC (Computer Numerical Control) drilling machine is mechanically similar to a standard drilling machine. However, it is automatically controlled via a computer that interprets a set of machine-readable instructions called G-code. A CNC drilling machine is more accurate and offers improved productivity when compared to standard hand-operated machines. 

2. Sensitive Drilling Machine

A sensitive drilling machine is designed for low-volume drilling of small-diameter holes. The feed rate of these machines is manually controlled by turning a wheel that drives the tool into the workpiece. It is called a "sensitive drilling machine" because a skilled operator is closely attuned to the feel of the work under the drill, and he can manually control the exact amount of pressure he applies to complete the drilling operation.

3. Radial Drilling Machine

A radial drilling machine has its spindle mounted on an arm that can be rotated around the column while also allowing the drill head, spindle, and feed mechanism to move radially along the arm. This machine allows the operator to drill in various locations without having to reposition the workpiece.

4. Upright Drilling Machine

An upright drilling machine is similar in construction to a sensitive drilling machine but is more robust. It typically has a power feed that automatically plunges the tool into the workpiece. Upright drilling machines are better suited to heavy-duty applications.

5. Gang Drilling Machine

A gang drilling machine has multiple independent columns, each with its own drive and spindle mounted to a shared base. These machines are typically used when multiple successive operations must be performed, for example, drilling and then tapping. A multi-spindle drill on the other hand is typically designed to drill multiple holes at once.

6. Deep-Hole Drilling Machine

Deep-hole drilling machines are typically used to drill holes with at most a 20:1 diameter to depth ratio. Deep-hole drilling machines are usually oriented horizontally to allow for larger workpieces to lay on their sides and require high-pressure coolant to be pumped to the cutting interface to flush chips away from the hole.

7. Multiple-Spindle Drilling Machine

A multiple-spindle drilling machine is designed to drill multiple holes into a single workpiece simultaneously, repeating that same hole pattern for every part. These machines are ideally suited to mass production of identical parts. Gang drilling machines have similar capabilities and are more flexible in terms of capabilities. 

8. Portable Drilling Machine

A portable drilling machine is hand-operated. It is used for light-duty drilling operations. A portable drill can be powered with a battery, pressurized air, or an electrical cable plugged into a wall socket. This is the perfect drill machine for home use. 

9. Micro Drill Press

A micro drill press is a small-drill machine whose feed is manually controlled, and designed to drill small holes with extreme precision. These machines are used in applications where tiny, accurate holes are required, as is the case for electronics or jewelry-making.

10. Turret-Type Drilling Machine

A turret drilling machine has multiple tools attached to a rotating turret. This type of machine is generally used for mass production drilling where many holes need to be drilled in the same piece with different sizes and depths. A turret-type drilling machine drills only one hole at a time.

What Are the Best Drilling Machines?

Deciding which is the best for a specific application can be difficult because there are many different types of drilling machines on the market. Listed below are some common use cases and the ideal drilling machine for each application:

1. Low Volume: The best machines for low-volume use are portable and sensitive drilling machines. 
2. Heavy Duty: For heavy-duty drilling, the best machines are the radial arm and the upright drilling machine.
3. High Volume:  If high production volumes are required, then the turret, multiple spindles, and gang drilling machines are best suited to the job.

Is a Drilling Machine Essential?

Yes, a drilling machine is essential for every workshop. Most workshops at the very least need a portable drill and a sensitive drilling machine. 

This article presented drilling machines, explained what they are, and discussed how and when they are used in manufacturing. To learn more about drilling machines, contact a Xometry representative.

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