Ever struggled with holes that just aren’t quite the right size or finish, even after careful drilling? If you want smoother, more precise results in your projects, you’re not alone—reaming drilling is the solution many professionals and DIYers rely on.
Understanding how reaming drilling works is crucial for achieving perfect holes in metal, wood, or plastic. In this article, we’ll explain exactly what reaming drilling is, when to use it, and offer practical, straightforward steps and expert tips for flawless results.
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Understanding How Reaming Follows Drilling
If you’ve ever needed an extremely smooth, accurately-sized hole for a mechanical part, you’ve probably heard about reaming and drilling. But what exactly is “reaming drilling,” and how do these processes work together? Let’s break down each process, see why and when you’d use them, and walk step-by-step through how to achieve the perfect hole.
What Is Drilling?
Drilling is the process of creating a round hole in a solid material, typically metal, wood, or plastic. This is usually the first step when you need to make a hole in a workpiece. The tool used, called a drill bit, rotates at high speed to cut into the material.
- Purpose: Make a hole where none exists.
- Tools Used: Drill press, hand drill, or CNC machine with a drill bit.
Key Characteristics of Drilled Holes
- Not perfectly round or smooth at the microscopic level.
- Size may be slightly less than the drill bit size due to tool flex or material spring-back.
- Tolerances are usually sufficient for everyday tasks, but not for high-precision engineering.
What Is Reaming?
Reaming is a finishing process done after drilling. While drilling gets most of the work done, reaming “refines” the hole: it removes a thin layer of material, making the hole smoother and more accurately sized.
- Purpose: Improve the smoothness and size accuracy of a previously drilled hole.
- Tool Used: Reamer – a multi-edged tool designed for precise cutting.
What Makes Reaming Special?
- It creates holes with tight tolerances and excellent surface finish.
- It’s not meant to fix major errors, but to dial in the final precision.
The Relationship Between Drilling and Reaming
Think of drilling and reaming as a tag-team approach. Drilling does the heavy lifting, getting you close to your target hole size. Reaming steps in next, giving you the accuracy, smoothness, and precision that seems almost impossible with drilling alone.
In Practice
- Drill the hole slightly undersized.
- Use a reamer to finish the hole to its final, exact size.
Step-by-Step: How to Perform Drilling Followed by Reaming
If you want a perfectly sized and smooth hole, follow these proven steps:
1. Select Your Drill Bit
- Choose a drill bit smaller than your final desired hole size.
- As a rule of thumb: Drill the hole 0.2–0.5 mm (for small holes) or about 0.007–0.020 inches (for larger holes) smaller than your target diameter.
2. Set Up for Drilling
- Secure the workpiece firmly using a vice or clamps.
- Position your drill above the intended spot.
- Use appropriate speed settings for the material (softer materials = higher speeds, harder materials = slower speeds).
3. Drill the Hole
- Gradually feed the bit into the material.
- Pull out periodically to remove chips and prevent overheating.
- After reaching the desired depth, remove the bit and check the hole.
4. Inspect the Drilled Hole
- Clear away debris.
- Ensure the hole is free from major burrs and obstructions.
5. Select and Prepare the Reamer
- Choose a reamer that matches your exact final hole size.
- Coat it with cutting lubricant if needed (particularly for metals).
6. Ream the Hole
- Insert the reamer gently into the drilled hole.
- Turn (by hand or machine) at slower speeds than drilling.
- Apply steady, low pressure—let the reamer do the work.
- Do not reverse the reamer while inside the hole, as it can mar the finish.
7. Inspect the Finished Hole
- Check the size with precision measuring tools (micrometer or gauge).
- Ensure the surface is smooth and round.
- Remove any remaining debris or burrs.
Benefits of Reaming After Drilling
Why take the extra step? Here’s why professionals and manufacturers often pair reaming with drilling:
- Exceptional Accuracy: Achieve highly controlled hole diameters, often within ±0.01 mm.
- Superior Surface Finish: Reduce friction, improve fits for shafts or fasteners, and eliminate roughness.
- Repeatability: Get consistent results across multiple holes.
- Improved Mechanical Properties: Smooth holes reduce stress concentrations, leading to stronger, longer-lasting assemblies.
Challenges of “Drilling and Reaming” – What to Watch Out For
Even though this combination brings great results, there are a few things to consider:
- Tool Misalignment: If the drilled hole is not straight, reaming can’t fix the misalignment.
- Material Choice: Some materials (like hard steels or plastics) can be tough to ream cleanly.
- Tool Wear: Both drill bits and reamers need to be sharp and in good condition for accurate results.
- Heat Buildup: Excess heat can dull tools and damage material—lubrication and proper speeds are essential.
Practical Tips and Best Practices
- Always Drill First: Never try to ream a hole in solid material; start with a drilled hole.
- Keep Tools Sharp and Clean: Dull tools can chatter, gouge, or mis-size your holes.
- Use Cutting Fluid: Lubrication improves finish, reduces heat, and extends tool life (especially in metals).
- Ream at Low Speed: Too high a speed causes poor finishes and rapid tool wear. Use about half the speed for reaming as for drilling.
- Clamp Securely: Vibration or movement leads to irregular or oversized holes.
- Check Hole Size Frequently: Especially important in precision work and when making multiple parts.
Cost Tips: Saving on Drilling, Reaming, and Shipping
If your project involves shipping parts, machines, or tools—which often comes up with precision manufacturing—here are some ways to control costs:
- Combine Shipments: Batch tool or part orders to minimize shipping fees.
- Source Locally: Procuring drill bits and reamers from local suppliers can save money and time.
- Use Standard Sizes: Designing holes to fit standard reamers (rather than custom sizes) reduces tool costs.
- Maintain Your Tools: Well-maintained tools last longer—fewer replacements mean lower long-term expenses.
- Plan Ahead: Avoid rush orders by forecasting your needs and scheduling purchases in advance.
The Difference Between Drilling, Reaming, and Related Hole-Making Processes
Let’s clarify what makes reaming unique versus similar techniques:
Drilling
- Purpose: Create a new hole.
- Tool: Drill bit.
- Accuracy: Moderate.
Boring
- Purpose: Enlarge or finish an existing hole (often in large components).
- Tool: Boring bar.
- Accuracy: Higher than drilling but not as fine as reaming.
Reaming
- Purpose: Refine an existing hole for diameter and finish.
- Tool: Reamer.
- Accuracy: Highest among standard mechanical processes.
Tapping
- Purpose: Cut threads inside a hole.
- Tool: Tap.
- Accuracy: Related to thread pitch, not hole size.
Types of Reamers: Choosing the Right Tool
There are several reamer variants, each suited for specific applications:
- Hand Reamers: Used manually with a twist or “T” handle, ideal for small projects or fine adjustments.
- Machine Reamers: Designed for use in drill presses or CNC equipment.
- Adjustable Reamers: Slide to vary the diameter, useful for custom one-off jobs.
- Tapered Reamers: Create or finish holes with a tapered profile, often used for fitting pins.
Choosing the correct type ensures smooth operation and accurate results.
When Should You Use Drilling and Reaming Together?
You’d combine drilling and reaming when you need:
- High-precision fit for a shaft, pin, or dowel.
- Very smooth holes—especially if the part moves with another (like in bearings).
- Critical tolerances in assembled mechanical systems (automotive, aerospace, manufacturing, tooling).
Summary
Drilling and reaming work hand-in-hand to make precision holes in metal, wood, and plastic parts. Drill first to create your basic hole, then ream for accuracy and a mirror-smooth finish. With care, sharp tools, and attention to detail, you’ll achieve professional-quality results every time—whether you’re an engineer, machinist, or hobbyist building your next masterpiece.
Frequently Asked Questions (FAQs)
1. Can I use a reamer instead of a drill bit to make a hole?
No. A reamer is designed to enlarge and finish an existing hole, not to create new holes from solid material. Always drill first, then use the reamer for precision.
2. What size drill bit should I use before reaming?
Select a drill bit that is slightly smaller than your final hole size—typically 0.2–0.5 mm smaller for metal, or around 0.007–0.020 inches smaller for larger holes. This leaves material for the reamer to remove.
3. How do I avoid damaging a reamer during use?
Use a sharp, clean reamer, appropriate cutting speeds (usually slower than drilling), and plenty of lubrication. Never reverse the reamer inside the hole, as this can dull or damage it.
4. What’s the difference between boring and reaming?
Boring enlarges and straightens a pre-existing hole, often using a single-point cutting tool. Reaming, however, fine-tunes the size and improves surface finish with a multi-edged tool for high precision.
5. Can reaming fix a misaligned or crooked hole?
No. Reaming only enlarges and improves the surface of an existing hole but follows its path. If the hole is already misaligned from drilling, reaming will not correct the angle or position.
With these steps, insights, and tips, you’re fully equipped to master the art of precise holes through drilling and reaming—the essential skills for countless mechanical and manufacturing projects!