Custom CNC Reamers Tools: Technical Guide for Precision Hole Finishing

Custom CNC Reaming Tools for Superior Hole Accuracy and Surface Finish

Modern manufacturing relies on the accuracy of hole finishing to ensure proper assembly, sealing capability, bearing alignment, and long-term part reliability. Although drilling creates the initial hole, accurate tolerances and a high-quality finish can be attained only by using special reamer tools.
Whatever industry you belong to, whether it is aerospace components, automotive, medical, or industrial parts, CNC reamers and precision reamers are key tools in making holes according to the engineering requirements.

In this article, you will learn about the use of reamers tools, why carbide reamers are extensively used, and what custom reamers are used for in CNC machining operations.

Quick Answer: What Are CNC Reamers?

CNC reamers are tools which are used for cutting purposes in order to make any pre-drilled holes with perfectly accurate diameters and improved surface finish. They take off just a little bit of material, which is usually 0.10 – 0.50 mm. CNC reamers are widely used in aerospace, automotive, medical, and industrial manufacturing.

What Are Reamers Tools?

Reamers are hole-finish cutting tools which are used to increase the size of an existing hole to a very high degree of accuracy. While drills cut away large amounts of material to create a hole, the reamer cuts away a small amount of material from the side of the hole, increasing its precision, roundness, cylindricity, and surface finish. The general operation of reaming takes place after drilling or boring operations and can be considered a finishing process.
Functions of reamers tools are:

• Highly precise hole size IT7-IT9

• Surface quality up to Ra 0.2 – 0.8 µm

• The correction of drilling errors

• Roundness and cylindricity improvement

• Proper fit for bearings, bushes, pins, and shafts

How Does CNC Reaming Work?

The CNC reaming process consists of the following steps:

Step 1: Drilling Pilot Hole

A hole which is somewhat smaller than the final hole to be produced is drilled.

Step 2: Alignment of CNC reamer

CNC reamer should be concentric to the hole.

Step 3: Provide Coolant

Coolant flow helps in lubricating the tool, removal of chips and increasing the life of the tool.

Step 4: Reaming Operation

The remaining portion of the tool removes the layer of metal around the hole drilled earlier.

Step 5: Inspect Final Hole

The hole after production must satisfy certain specifications such as diameter, roundness, cylindricity and finish quality.

What Are the Different Types of CNC Reamers?

Various types of reamers made up of various materials are needed for various purposes.

1. Straight Flute Reamers

Straight flute reamers provide good stability and hence can be used for a variety of purposes like for small holes and general machining. Suitable for:

• Cast iron

• Aluminum

• Brass and bronze

• Small hole machining operations

2. Spiral Flute Reamers

Spiral flute reamer provide good chip clearance and reduce chatter and therefore can be suitably used for deep hole machining and high volume CNC machining.
Suitable for:

• Deep hole machining

• Stainless steel

• Titanium

• CNC machining processes

3. Taper Reamers

This type of reamer is applied in tapering holes where an angled surface is required.

4. Adjustable and Expansion Reamers

These can make certain adjustments to the diameter and are often used for maintenance and repair operations.

Why Precision Reamers Are Critical for Precision Hole Machining

Precision reamers are employed by manufacturers when precise hole is essential for the functionality of the parts.

The advantages include:

• Improved Dimensional Accuracy: Precision reamers give precise holes for mass production.

• Surface Finish: The improved surface finish reduces friction and increases efficiency of sealing.

• Shape of Hole: Improved shape of the hole.

• Shaft Alignment: Correctly assembling the shaft, bearings, dowel pins, and bushings.

Carbide Reamers vs HSS Reamers

One of the frequently asked questions in the process of CNC reaming is whether to use either carbide reamers or HSS reamers.

Carbide Reamers

• Excellent tool life

• High cutting speed

• Dimensional stability

• Suitable for mass production

• Suitable for stainless steel, titanium, and hardened steel

• Expensive initially but low cost of tooling

HSS Reamers

• Moderate tool life

• Moderate cutting speed

• Low initial cost

• Can be resharpened

• Suitable for mass production

• Suitable for soft metals

Why Choose Custom CNC Reamers?

Standard reaming tools can have a variety of applications, but customized manufacturing may call for custom reamers.

Advantages of custom reamers:

• Application Shape: Custom flute shape allows optimal cutting properties for particular application materials

• Proper Chips Removal: Custom flute shape prevents chip accumulation in deep holes

• Easy Maintenance of Tools: Custom coating and carbide types increase tool lifetime

• Faster Machining Process: Custom shape allows faster machining process

• Better Holes Geometry: Custom reamers make better holes geometry

How to Select the Right CNC Reamer

Different factors can be considered when choosing reamer tools.

1. Material of the Workpiece: Depending upon the material type, certain requirements are made concerning flutes, coating, and carbides.

2. Tolerance of the Hole: For certain circumstances, you will have to select either Precision reamers or custom reamers.

3. Hole Depth: For deep holes spiral flute is more preferable because of chip ejection issues.

4. Volume of Production: Large volume production usually justifies usage of carbide reamers.

5. Delivery of Cutting Fluids: It makes sense to use through-coolant reamers.

Frequently Asked Questions

1) What are reamer tools used for?

Reamers tools are applied to enlarge and finish previously drilled holes to required sizes and improve the surface quality, roundness and precision of holes.

2) What is the difference between drilling and reaming?

Drilling is the process of creating holes, whereas reaming is a finishing process of improving hole diameter accuracy, geometry and quality of surface.

3) How much material should a reamer remove?

Mostly during the reamers operation from 0.10 to 0.50 mm of material is removed, depending on workpiece material, hole size and tolerances.

4) Why are carbide reamers preferable in CNC machining?

Carbide reamers offer longer tool life, high speed of cutting, increased resistance to wear and better hole dimension consistency than HSS reamers.

5) When should manufacturers choose custom reamers?

Custom reamers should be used by the manufacturer in the case of inability of using standard tools according to special demands.

Conclusion

As tolerance demands increase in manufacturing, the significance of performance reamers tools becomes ever more important. It is important to have CNC reamers, precision reamers, and carbide reamers in order to achieve precision holes having excellent surface finishes, roundness, and tolerances. Whether you need standard reamers or specialized reamers, contact Baucor for selecting the correct reamer will help in increasing efficiency, saving waste material, and extending tool life.