Drilling vs Boring vs Reaming: Detailed Comparison

Drilling, boring, and reaming are three important machining techniques in manufacturing. Each produces or modifies holes with special methods.

In this blog, you will study the differences between drilling vs boring vs reaming, their resemblances, applications, and how to choose the best method for accurate hole-making.

What is Drilling?

Drilling creates a fresh cylindrical hole using a turning end-cutting tool. The tool is a drill bit with channels that cut and remove chips. You use drilling to start most interior features before any finishing step.

Compared with other methods, drilling is fast, efficient, and affordable. It does not have perfect adjustment or smoothness. Think of it as the first pass that removes magnitude material.

How Drilling Works?

• Spot the drill vertical to the surface.
• Place spindle speed and convey to match the material.
• Provide centrally while flutes carry chips out.
• Use step drilling or through-tool refrigerant for deep holes.
• Refine and measure before any supporting process.

Types of Drilling

Twist Drilling

Twist drilling is the most familiar and commonly applied drilling technique. It uses a drill bit with spiral flutes that cut into the material while simultaneously removing chips from the cutting zone.

This technique delivers results for most metals, plastics, and composites, making it applicable for multiple-purpose hole-making across a large variety of diameters. Its flexibility, twist drilling is usually the default choice in machining processes.

Deep Hole Drilling

Deep hole drilling is used when the hole depth surpasses ten times its cross-section. Standard drills face difficulty with chip removal and tool deviation in such cases, which can lead to deviations or tool failure. To resolve this, special drilling steps, pilot holes, and modern coolant control systems are used.

Deep hole drilling confirms accuracy, straightness, and consistent chip removal in applications like die-making, aerospace, and oil drilling.

Gun Drilling

Gun drilling is a specially engineered process for the manufacture of holes with a particularly high length-to-diameter ratio. Such holes are made with single-edge cutting tools, which have internal coolant channels meant for fast chip removal. This technique assures perfect alignment and remarkable coating under conditions that still bring about close variations.

Trepanning

Trepanning is a unique drilling technique that removes a round of material while leaving a solid core. Instead of turning the whole hole into chips, trepanning takes out the material in one piece, which can save natural resource costs and decrease power consumption.

This technique is perfect for generating large-diameter holes in thick materials, normally applied in pressure container processing, marine fabrication, and heavy engineering applications.

Advantages and Disadvantages of Drilling

Drilling is the best way to make holes. It prepares the following finishing operations. Discover the trade-offs below:

Advantages

• Establish an opening very rapidly.
• Tooling expense is also the lowest in most cases.
• Well-suited with extensive materials.
• Simple programming and setup.
• A high processing rate is possible in CNC machining.

Disadvantages

• Balanced accuracy and roundness.
• Surface finishes are rougher than would be obtained using finishing techniques.
• Wander may affect the true position.
• May require boring or reaming afterward.

Drilling Applications

• Guide holes for finishing, sizing, and forming.
• Spacing holes for fixings and bolts.
• Liquid, coolant, and wiring channels.
• High-volume manufacturing of common holes.

What is Boring?

Boring makes an existing hole larger and straight, using a single-point tool. It has the accurate size, alignment, and geometry after drilling or casting. Boring enhances roundness, straightness, and location.

The boring can be performed in mills. Boring is much slower than drilling, yet it provides the highest degree of control over diameter and axis.

How Boring Works?

• Begin with a hole pre-drilled or cast.
• Engage a boring bar or boring head being supplied by a single insert.
• Light cuts are taken while monitoring the deflection and chatter.
• Set the offset to exceed the target diameter.
• Confirm the alignment and actual position.

Types of Boring

Horizontal Boring

Great for the whole parts that do not rotate. The bar is held up, and bending is controlled.

Vertical Boring

Good for big, heavy workpieces. It will use gravity for chip evacuation at vertical machines.

Line Boring

Aligns a series of aligned holes in position, usually done in repair and heavy equipment.

Back Boring

For a larger counter-diameter, back boring is often used when an exit is needed.

Advantages and Disadvantages of Boring

Boring is the accuracy step before ultra-fine finishing. Know its strengths and its weaknesses.

Advantages

• Aligns and makes concentric.
• Precision size control with adjustability.
• Improves roundness and straightness.
• Large diameter.
• Blind and through holes.

Disadvantages

• Cannot make a hole by using a solid.
• Slower than drilling to remove stock.
• High risk of tool chatter on long overhangs.
• Requires skilled setup and inspection.
• The cost of tooling increases as the depth and size increase.

Boring Applications

• Bearing and bushing seats.
• Good accuracy in housings and gearbox bores.
• Features of the engine block and cylinder.
• Large valve and manifold bores.
• Aligns split-case machinery.

What is Reaming?

Reaming is a multi-edge finishing operation that helps bring a ready-made hole to size with a smooth surface. It removes little allowance. When the final fit and finish are crucial, reaming becomes the choice.

Reaming cannot remove location errors. In addition, it can be the perfect size. So to be successful, keep alignment errors to a minimum before reaming.

How Reaming Works?

• Drill small or bore close to size first.
• Leave a consistent stock allowance for the sizing tool.
• Align the tool carefully with the drilling axis.
• Use a steady feed and sufficient lubrication.
• Calculate regularly to confirm size.

Types of Reamers

Straight Reamers

Reamers that have a constant diameter with straight flutes. Common purpose for through holes and various materials.

Taper Pin Reamers

To produce tapered holes for taper pins. Useful for the alignment with mechanical locking.

Shell Reamers

Large diameter reamers that fix on an arbor. Cost-effective for large holes.

Adjustable Reamers

A flexible blade design that covers a small size range, handy for maintenance and repair.

Advantages and Disadvantages of Reaming

Reaming is the final sizing step when variations and finish matter. Manage input quality for best results.

Advantages

• Very tight diametrical tolerances are maintained.
• Excellent surface finish is obtained.
• Quick cycle for light stock removal.
• Good tool life with lubricant.
• Predictable and repeatable.

Disadvantages

• Cannot produce holes or set the location accurately.
• Stock allowance can be required to be evened.
• Sometimes it is difficult to avoid burning in the bore due to heat and bunches of chips.
• Not good for interrupted cuts.
• Limited capability to improve out-of-round holes.

Reaming Applications

• Dowel and pin holes with press fits.
• Precision bores for jigs, fixtures or tools.
• Hydraulic and pneumatic valve housings.
• Accurate fitting for medical and aerospace applications.

Drilling vs Boring vs Reaming: Comparison Table

What are the Similarities between Drilling, Boring, and Reaming?

• All are material-removing, removal-oriented hole-making processes.
• All can run on CNC and for drills.
• All benefit from tight holding and coolant.
• You can join them in one program.
• Each needs proper chip control.

Different Types of Holes

Through Hole: Completely passes through the workpiece.

Blind Hole: Ends before breakout, depth must be controlled closely.

Threaded/Tapped Hole: Has internal threads for securing fasteners.

Counterbore: Flat-bottom step to accommodate bolt heads.

Tapered Hole: Typically, changes in diameter along the axis for pins or seals.

What’s the Best Hole-Making Method for Tight Tolerances?

Apply a process, not as a one process. Most parts should have a pilot drilled, then bored for alignment, followed by reaming to the size. In this order, location geometry and finish are managed. The feature begins during drilling, while boring finalizes the axis and roundness. For this specific comparison, reaming will give the exact size and finish after prior sizing.

Practical allowances:

• 0.10-0.30 mm stock to leave for reaming small holes.
• 0.05 to 0.10 mm from the final size to approach for boring accuracy.
• Verify runout, clamp rigidity, and coolant before finishing.

Conclusion

You now understand the difference between drilling, boring, and reaming, where each is accurate. Using drilling for creation, boring for geometry, and reaming for final sizing.

Need tight-tolerance holes without guesswork? DEK provides CNC drilling, boring, and reaming with DFM support and fast lead times. Share your drawings, and we will recommend the optimal route for cost, speed, and accuracy.