Drilling is one of the most commonly used machining operations for almost every project.
A pillar drill provides the ability to drill accurate holes with good precision and a high surface finish.
But what exactly is a pillar drill and what makes it different from other standard drills?
A pillar drill is a vertical drilling machine that consists of a rigid pillar that supports all the other components of the drill. These machines provide variable speed control, making them suitable for drilling a variety of materials. Generally, these drills are available in full-size and benchtop (drill press) versions.
This article provides a detailed guide on pillar drills by going through their parts, advantages, operations, etc. In the end, the article also differentiates between a pillar drill and a bench press.
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What is a Pillar Drill? How it Works
A pillar drill is a free-standing machine with a metal pillar (or column) attached to a base plate that is bolted or securely fastened to the floor, hence called a “Pillar Drill”.
It consists of a powerful motor that rotates the drill bit, providing the ability to drill or tap holes in workpieces with variable thicknesses.
A pillar drill consists of an adjustable table that holds the workpiece firmly, by means of a clamping technique.
The table can be raised/lowered or tilted at the required angle to drill the desired holes in the workpiece.
With the help of a handle, the drilling spindle will be lowered until the drill bit reaches the required depth.
Most of the time, a pillar drill stands on the floor by itself. However, there are smaller versions of pillar drills called drill press or bench drills. However, you may hear them all referred to as pillar drills at some point.
What is a Pillar Drill Used For? 8 Operations
A pillar drill can be used to perform various types of operations.
Drilling is simply the process of making holes in the workpiece.
It can also be used as an initial step for many other operations like boring, tapping, threading, etc.
Pillar drills are ideal for drilling several holes in quick succession with precise depth and dimensions.
The size of the drilled hole depends on the drill bit used.
Boring is the process of enlarging a previously drilled hole in a workpiece using a single-point cutting tool.
You can use it to accurately size and finish the hole, as well as straighten the drilled, cast, or forged holes.
Apart from that, it can also be used to perform counterboring, which is a type of boring operation where the hole is enlarged up to the diameter of the boring tool.
In reaming, a multi-tooth rotary cutting tool called a reamer is used for enlarging and finishing already drilled or bored holes, to achieve the desired surface finish and dimensional accuracy.
Using a reamer provides the ability to achieve a dimensional tolerance as high as 0.001".
The amount of stock provided for reaming is determined by the quality and size of the hole.
A general rule of thumb is that drilled holes should maintain around 0.010" to 0.015" tolerance for reaming operation.
For small diameter holes, such as 1⁄32", the tolerance for reaming should be between 0.003" to 0.006".
Countersink is the process of making a cone-shaped cut at the top of the hole.
It is carried out to remove the burrs from the edges of holes, and to provide a flush fit for flat-headed fasteners.
Tapping is the process of producing internal threads in a cylindrical hole.
A pillar drill can be used for tapping (to cut threads), however, it cannot be used for thread milling (external threads on workpieces).
What Materials can a Pillar Drill Work on?
The following are some materials that a pillar drill can drill into:
- Metal (steel, and aluminum)
- Wood (hardwood, softwood timber, and plywood)
- Sheet material
- Acrylic (thermoplastics)
Drilling holes in a metal can be challenging due to their high durability and rigidity.
Generally, drilling metal is a slow process that involves an extremely slow feed rate and high power, with a constant flow of cutting fluid to prevent the drill bit or the workpiece from overheating.
Holding a hand drill steady for prolonged durations is physically impossible leading to inaccuracy in the drilled hole.
Therefore, a pillar drill eliminates this limitation, providing the ability to maintain a steady drilling position with a uniform feed rate, which results in an exactly 90-degree hole in the metal, with no offset.
When using a pillar drill for machining metal, it is important to select the right tool for the application.
The selection of the speed for wood depends on the diameter of the drill bit and the type of wood being machined.
The larger the diameter of the drill bit, the slower the recommended speed, and increasing the speed beyond the optimal value might result in wood burning or damage to the drill bit.
Generally, when using a 3/8" drill bit, it is recommended to drill softwood at 3000 RPM, whereas hardwood requires a lower speed of around 1500 RPM.
Drilling engineered wood like particle board, MDF, and plywood can generate harmful fumes of formaldehyde and is therefore advised to wear a safety mask when drilling wood.
Drilling acrylic can be challenging if not performed with the utmost care, as it has the tendency to soften or melt under the action of heat generated during drilling.
As a result, if your application requires drilling large holes in acrylic, it is advised to drill small holes and then gradually enlarge them to prevent overheating of the workpiece.
Therefore, laser cutting acrylic is preferable over drilling it.
Advantages of a Pillar Drill
High accuracy and precision
As pillar drills are firmly clamped to the floor and are more stable, they provide the ability to drill perfectly straight drill holes.
Whereas in the case of hand drill the accuracy relies on the ability of the operator to hold the drill steady throughout the operation.
In pillar drill, the workpiece is held rigidly on a table and the drill bit moves down in a straight line perpendicular to the workpiece.
This drill bit is powered by a powerful motor, which is comparatively heavier and provides more torque than hand-geld drills.
As a result, the overall quality of the holes will be much higher than the handheld drill holes.
High Material Flexibility
With a pillar drill, you can exert more force than with a hand drill. This makes it suitable for working on hard materials like hardwood, steel, etc.
Apart from that, its versatile worktable provides the ability to hold workpieces if different sizes and drill holes at different angles.
Pillar Drill vs Drill Press
|Parameters||Pillar Drill||Drill Press|
|Construction||Mounted on the Floor, more stable and accurate||Benchtop machine|
|Size||Large size with adjustable table||Require less space|
|Power||High power, suitable to drill larger pieces of materials and produce larger holes||Comparatively less powerful, suitable small-scale projects|
|Portability||Comparatively heavy, and not portable||Easily movable|
|Applications||Suitable for heavy-duty project||Suitable for light components with low-depth holes|
|Cost||Comparatively higher||Comparatively lower|
Pillar drills and drill presses are generally similar machines with differences in their construction and applications.
A pillar drill is generally large in size and is mounted on the floor. It has superior speed and power to benchtop drill presses and is capable of drilling holes accurately in comparatively thicker materials.
Drill press or bench drill is smaller in size and can be placed on a workbench or a table. It requires less space and can be easily moved from one place to another.
Pillar drill has a wide range of speed control and a variety of materials can be drilled easily.
Pillar drills are suitable for heavy-duty projects where the material is thicker than 4 inches, whereas drill presses are suitable for small home decor DIY projects.
The cost of the pillar drill is almost two times more than the drill press.
Parts of a Pillar Drill
Pillar Drill mainly consists of various parts that work in synchronization to get the desired drilling output.
Motor and Drive system
The top unit of the pillar drill is called the head. It is the powerhouse of the pillar drill as it consists of the motor that drives the drill.
The motor is connected to the spindle through a pulley or gear drive system, which is then connected to the drilling chuck.
This drive system provides the ability to control the spindle speed, making it suitable to drill a variety of materials ranging from wood to metals.
The power and speed of the motor determine the capability of the pillar drill, which thereby determines the types of materials it can work on.
A pillar drill consists of a hand wheel that provides the ability to control the feed rate by moving the spindle up and down into the workpiece.
On the head, you can also find a depth adjustment scale, a lock for spindle movement, and a guard for the drive system.
The drill table, also called a worktable, is a round or square-shaped thick plate attached to the pillar, that houses the workpiece to be drilled.
Depending on the height of the workpiece, the worktable can be raised or lowered on the column using a rack-and-pinion mechanism with a handwheel connected at the back of the worktable.
The worktable will hold the workpiece firmly during the drilling operation so that it does not move out of position, which could result in an incorrect-sized hole or an accident.
Generally, drill tables contain diagonal grooves or slots that facilitate the attachment of a machining vice or an additional pillar drill worktable.
Many pillar drill machines also have the facility of tilting the worktable. This is useful if you need to drill at an angle other than 90 degrees.
The pillar or column is a hollow vertical cylinder mounted on the rear of the base.
It supports the rest of the pillar drill parts such as the worktable, drill head, and all other mechanisms which are attached to the head.
Therefore, the column/pillar acts as the backbone of the pillar drill, providing support for all the other components.
Apart from that, the rigidity of the pillar determines the ability of the pillar drill to machine holes with no or minimal vibrations, thereby achieving higher accuracy.
The base is the foundation of the pillar drill and provides support to absorb shock and vibrations transferred via the pillar.
It is a robust, thick piece of high-quality industrial cast iron with a flat horizontal surface.
Generally, pillar drills have a heavy base that acts as a counterweight and prevents the drill from tumbling.
Apart from that, the base also acts as a secondary worktable for housing larger workpieces, which cannot fit the primary worktable of the drill.
Although not an integral part, drill bits play an important role in the operation of a pillar drill.
These are the cutting tools used to remove the material from the workpiece and perform the required operation.
Generally, multi-point helical groove drilling bits are used for drilling holes, but a pillar drill can also be used with other tools.
Depending upon the type of tool used, a pillar drill can be used to perform drilling, bearing, rotary broaching, tapping, reaming, threading, etc.
Pillar drills are an essential machine tool when highly accurate holes need to be made in the workpiece.
Compared to hand drills, pillar drills provide many advantages such as high accuracy, adjustable table, perfect alignments, and thick pieces of materials.
A benchtop drill press might be a cost-effective tool for light home decor projects, whereas a full-size drill press is recommended for industrial applications.
Furthermore, while drilling wood, improper parameters can lead to fire hazards, making it important to use safety equipment all the time.
Frequently Asked Questions (FAQ)
How is a pillar drill different from a radial arm drilling machine?
The difference between a pillar drill and a radial arm drill depends upon the movement of the drill head. In the case of the pillar drill, the drill head is fixed on the column. A radial drilling machine has a head that can slide across the length of the arm. The arm can be raised/lowered or rotated.
Can I use a pillar drill for milling?
Yes, a pillar drill can be used for milling by manually moving the workpiece along the desired path. However, it is only suitable for milling shallow grooves in soft materials like plastics and softwood.
Is cutting fluid required when drilling wood on a pillar drill?
No, cutting fluid is not required when drilling wood because the fluid will soak into the wood, discoloring it and causing wood fibers to swell.