Guide to Reaming: Processes, Tools, and Applications

type of reamers
Jack Lie CNC machining expert

Specialize in CNC Milling, CNC Turning, 3D Printing, Urethane Casting, and Sheet Metal Fabrication Services.


Reaming, a finishing process or hole machining, plays an essential role in the accuracy and surface quality of machined parts. Furthermore, this technology is widely employed across diverse industries due to its several benefits like dimensional control.

Therefore, this article will introduce the reaming process in detail, covering its definition, different types of reamers, as well as applications. It aims to provide readers with a comprehensive and practical reaming guide.

What is the Reaming Process?

Reaming refers to a precision cutting process that performs an operation on a pre-existing hole. More specifically, it’s meant to accurately widen the existing sizes and improve the surface quality of the hole. Generally, manufacturers utilize a reamer, which is a multi-tooth cutting tool, to remove a minute quantity of material from the hole wall. In addition, this process helps to produce a smooth, cylindrical hole with tight dimensional tolerances.

How To Ream a Hole?

Reaming typically occurs on certain machine tools such as milling machines or lathes. It is crucial to understand some basic steps about how to ream a hole as it enhances the quality of components.

  1. Fix the workpiece on the machine tool with clamps.
  2. Prepare the necessary reamers that are 1.5 size of the holes.
  3. Using a larger spot drill to accurately drill the hole while avoiding the center drill.
  4. Use the appropriate speed and feed rate to start reaming.
  5. Regularly check the size and surface roughness of the hole and make adjustments if necessary.
  6. Remove any small burrs or rough edges with burr removers or files.

Types of Reamers

Each type of reamer has its unique process for various applications such as bearings and bushings. Below are some common types of reamers.

Hand Reamer

As the name suggests, hand reamers are manually operated tools that act on reaming metals or other hard materials. They often feature a helical flute and slight taper, which helps guide the reamer into the pre-drilled hole. In addition, it is well-suited for small batches or one-off production.

Hand Reamer

Floated Reamer

This type of reamer usually contains one or more spring-loaded guide elements. Further, these elements can move freely in the axial and radial directions to adapt to irregularities in the hole wall. Additionally, the floated reamer can automatically compensate for hole wall deviations during reaming to ensure hole roundness and straightness.

Spiral-Fluted Reamer

Spiral-fluted reamers have helical flutes that spiral around the tool body. They are also well-suited to cut hard materials like stainless steel. Furthermore, the feature of the helical angle also contributes to evacuating chips.

Straight-Fluted Reamer

This type of reamer is similar to the spiral-fluted reamer. However, the key distinction is that the straight-fluted reamer has flutes that run parallel to its central axis, rather than in a helical pattern. Generally, users often use it to ream materials like brass and cast iron.

Taper Pin Reamer

Taper Pin Reamers are designed for machining tapered holes with a straight-fluted design.

Adjustable Reamer

Users can adjust this reamer in size to machine holes with specific tolerance requirements.

Reaming Operations: Common Problems and Tips

Common Problems:

Dull or worn reamers, an excessive feed rate, insufficient rigidity in the setup, or inadequate lubrication can contribute to the following issues:

  • Chatter and vibration
  • Undersized or oversized holes
  • Burrs and torn edges

Tips:

  • For hard materials, start by using a smaller reamer to drill the hole, and then with a larger one accordingly.
  • Maintain a slower rotational speed, between 1/2 to 2/3 of the speed used when drilling the hole, but double the feed rate.
  • Use an 82ºor 90º countersink to chamfer the top edge of the hole.
  • Create a smooth finish with coolant or cutting oil.
  • Replace the reamer when performance starts to degrade.

Pre-Ream Drill Size Chart

Cutting Operations: Drilling VS Reaming VS Boring VS Tapping

All of these processes are meant to create or adjust the shape or diameter of holes. Yet they yield distinct benefits in practical uses. This section will thus introduce the differences among them.

Drilling:

CNC drilling is to create a new hole in a workpiece. Manufacturers generally use a drill bit to remove material and form the hole on a drill press or CNC machine. This process serves as a preparation for subsequent hole processing. Additionally, the drilling precision typically ranges from IT13 to IT11, while the surface roughness can vary from Ra 50 to 12.5 μm.

Reaming:

As mentioned previously, the reaming process involves enlarging and finishing a pre-drilled hole to a precise diameter. The goal is to achieve tight tolerances and a smooth surface finish using specialized reamer tools. Additionally, the reaming accuracy generally falls within the IT9 to IT6 tolerance range, while the surface finish value can reach Ra 3.2 to 0.2 μm, which is more precise than the drilling process.

Boring:

Similar to reaming, boring is also employed to enlarge an existing hole to a desired diameter, typically using a boring mill. However, the boring process can achieve a higher level of accuracy and precision compared to the remaining one.

Tapping:

Tapping is to create internal threads inside a pre-drilled hole with a tap tool. Furthermore, it allows for the insertion of threaded fasteners, such as bolts or screws.

These cutting operations serve different purposes in manufacturing parts and components. Each one has its own set of best practices, tools, and considerations to achieve the desired results.:

In summary, the choice of operation depends on the specific requirements of the part, the desired hole size and tolerance, and the available machinery and tools.

Other Finishing operations: Deburring VS Honing VS Filing

These three processes widely see in post-machining to optimize the surface finish, dimensional tolerances, and the overall quality of workpieces.

Deburring:

Deburring is to remove burrs, sharp edges, or excess material from a workpiece. Manufacturers usually take advantage of deburring tools including files, abrasive stones, or specialized deburring tools.

Honing:

Honing is improving the dimensional accuracy of a pre-machined hole or bore using honing stones or abrasive tools.

Filing:

At last, filing offers a manual approach for finishing and shaping parts, particularly for small or intricate features. This is achieved through the use of hand files with varying shapes and levels of coarseness.

Applications of Reaming 

Reaming is a versatile finishing operation that finds applications across various industries. Here are some key applications of reaming in different sectors:

  • Medical Industry: Orthopedic implants, surgical instruments, and other medical equipment.
  • Green Energy Industry: Wind turbines, solar panels, and hydroelectric dams facilitate.
  • Automotive Industry: Transmission, suspension, and steering system components.
  • Electronics Industry: Circuit boards, sensors, and optical devices.
  • Aerospace Industry: landing gear, airframes, and weapons systems.

Apart from the general applications, reaming machining also plays a crucial role in the production of bearings and shafts.

Conclusion

Now we can get a comprehensive overview of the reaming process. It covers the fundamentals of reaming, the different reamer types, common issues, and best practices, as well as comparisons to other cutting and finishing processes. Overall, the content offers readers a thorough understanding of the reaming process and its essential role in modern manufacturing and engineering.

Furthermore, Runsom Precison offers high-quality hole machining services to ensure you get perfectly formed holes for your engineering needs. We have experienced machinists who utilize advanced reaming techniques and equipment to deliver precise. Please feel free to contact us or ask for an instant quote.


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