Keyway slot broach example workpiece Gisstec

Ultimate Guide to Keyway Broaching on CNC Lathes in 2024

Posted on by gisstec

Introduction

Keyway broaching (keyway slotting, key slotting) is an essential machining process used to create internal slots or keyways in a workpiece, such as a gear. These keyways enable power transmission between the workpiece and a coupling component, such as a shaft. 

Keyway slot broach example workpiece Gisstec

Traditionally, dedicated broaching or slotting machines have been used for keyway broaching. However, thanks to CNC (Computer Numerical Control) technology, this process can now be performed more efficiently and with greater precision on CNC machines, including lathes (turning machines) and machining centers.

This not only streamlines the process but also eliminates the need to unclamp and reclamp the workpiece.

This comprehensive guide will provide an in-depth look at the keyway broaching operation specifically on CNC lathes, covering the following aspects:

  1. What is Keyway Broaching?
  2. Advantages of Keyway Broaching on CNC Lathes
  3. Tooling Selection for Keyway Broaching on CNC Lathes
  4. CNC Lathe Setup and Programming for Keyway Broaching
  5. Best Practices for Keyway Broaching on CNC Lathes
  6. Troubleshooting Common Keyway Broaching Issues on CNC Lathes
  7. Conclusion

1. What is Keyway Broaching?

Keyway broaching is a machining process that involves removing material from a workpiece to create an internal slot or keyway, which is crucial for the transmission of torque between mechanical components, such as gears and shafts.

How it has been done

This operation has been traditionally done on broaching machines using a broach, a long and slender cutting tool with a series of progressively larger teeth or cutting edges along its length.

This geometry allows the broach to gradually remove material from the workpiece as it is pulled or pushed through it until the final size of the keyway is achieved. Commercially they are purchased in a keyway broach set or as a single broach for a specific size.

How to do it now

However on CNC machines an indexable cutting tool (also referred to as insert, broaching insert, slotting insert or keyway cutter) is used, which can be replaced when worn out or chipped, eliminating the need to replace the entire tool.

The insert is first fixed to an insert holder (broaching tool, broaching holder) which is then typically clamped to a boring bar holder either on a VDI or BMT tool, depending on the machine’s turret type. 

To perform the broaching operation, the workpiece is clamped on the lathe chuck or a fixture. Material is then progressively removed with each pass of the broaching tool until the final keyway size is achieved.

The keyway’s depth is controlled by the X-axis feed, its length by the Z-axis feed, while the width of the keyway is determined by the broaching insert’s width.

Types of Broaching on CNC Lathes

This article is for static broaching tools where the movement of the machine’s turret is used for the  broaching process. Static broaching tools are recommended for smaller batches.

For high-speed broaching where the movement on the Z-axis is provided by the live tool, which is recommended for larger batches and serial production, read the following article instead: Live broaching tools (also known as live broaching unit, driven broaching tool, driven broaching unit, driven broaching head)

2. Advantages of Keyway Broaching on CNC Lathes

Keyway broaching on CNC lathes offers several advantages over traditional broaching machines:

  1. Flexibility: Indexable inserts allow for a great flexibility with various tolerances (such as H7, JS9, P6, D10, C11) and profiles (square, hexagon, spline) at a relatively low cost.
  2. Precision and Repeatability: CNC lathes offer high levels of precision and repeatability, ensuring consistent and accurate keyway dimensions across multiple workpieces. This precision is essential for achieving the proper fit between the key and the keyway, which is critical for reliable torque transmission.
  3. Reduced Setup Time: Cutting keyways on a CNC lathe eliminates the need for dedicated broaching machines and reduces setup time.
  4. Reduced Logistics Efforts: An alternative approach is outsourcing the work to a contract manufacturer. However, this creates additional logistical efforts such as batching, labelling and shipping the parts.
  5. Cost-Effectiveness (Machine): As CNC lathes can perform multiple operations, using a single machine can save on costs associated with acquiring and maintaining dedicated broaching machines.
  6. Cost-Effectiveness (Tooling): Traditional multi-tooth broaches that are used on broaching machines are relatively expensive. This makes buying and keeping multiple sizes and tolerances costly.

3. Tooling Selection for Keyway Broaching on CNC Lathes

Consider the following factors when selecting broaching tools for keyway broaching on a CNC lathe:

Broaching Slotting Tools Gisstec
  1. Insert Material: Common broach materials consist of high-speed steel (HSS) and carbide. In high-speed broaching operations, like those involving live broaching tools, carbide inserts usually result in a longer cutting tool lifespan. On the other hand, for lower-speed operations, such as with static broaching tools that operate in conjunction with turret movement, HSS alloy inserts may yield superior surface quality and tool durability.
  2. Insert Geometry: The broaching insert’s geometry should match the desired keyway dimensions, including width, depth, and profile. Standard broaching inserts are available in various sizes and tolerances for keyways, and shapes such as square, hexagon and spline profiles. Custom inserts can also be designed for unique keyway geometries and tolerances.
  3. Coating: Insert coatings can enhance the cutting performance and extend the tool life. Common coatings include Titanium Nitride (TiN) and Titanium Aluminum Nitride (TiAlN) for harder workpieces, which improve wear resistance and reduce friction between the broach and the workpiece material.
  4. Insert Holder: An insert holder is required to secure the insert in the CNC lathe’s turret. The holder is typically clamped to a boring bar holder, usually with a VDI or BMT interface depending on the machine turret. The holder should provide adequate support for the broach during the machining process.

4. CNC Lathe Setup for Keyway Broaching

Setting up a CNC lathe for keyway broaching involves the following steps:

  1. Tool Setup: Screw the broaching insert to the insert holder. Then clamp the insert holder to the appropriate boring bar holder on the CNC lathe’s turret. Ensure that the insert and the holder are securely clamped and aligned with the workpiece’s keyway location.
  2. Workpiece Setup: Clamp the workpiece on the CNC lathe, ensuring that it is properly aligned with the insert.
  3. CNC Program: Write a CNC program for the keyway broaching operation. Specify the cutting parameters, such as feed rate and depth of cut and coolant application if available.
  4. Broaching Process: The CNC lathe moves the broaching insert along the keyway length, progressively removing material with each pass. The depth of cut is incrementally increased until the desired keyway size is achieved. Unlike traditional multi-tooth broaches, the single-tooth broaching insert performs multiple passes to create the keyway.
  5. Test: Conduct a test run of the CNC program to verify a smooth keyway broaching operation, free of collisions or errors.
  6. Broaching & Finishing: Upon achieving the desired keyway dimensions on the workpiece, retract the CNC lathe turret and remove the workpiece. Inspect the keyway for accuracy and complete any necessary finishing processes.

5. Best Practices for Keyway Broaching on CNC Lathes

To achieve optimal results when performing keyway broaching on CNC lathes, follow these best practices:

  1. Optimize Cutting Parameters: Select appropriate cutting parameters, such as feed rate and depth of cut, based on the broach material, workpiece material, and keyway geometry. Optimizing these parameters will ensure efficient material removal and minimize tool wear.
  2. Use Appropriate Coolant: Apply coolant during the keyway broaching process to reduce heat generation, prevent tool wear, and improve surface finish. Choose a coolant that is compatible with both the workpiece and broach materials.
  3. Cutting a Keyway in a Blind Hole: To ensure effective chip removal in a blind hole, the cutting edge of the insert must pass through the full length of the keyway into a relief groove. Without proper chip evacuation, the chips can accumulate and cause issues like breakage of the insert. To avoid this, calculate the diameter and length of the relief groove based on the keyway width and depth.
  4. Ensure Proper Alignment: Ensure that the broach is properly aligned with the workpiece’s keyway location before starting the machining process. Misalignment can result in uneven keyway dimensions and excessive tool wear. If your lathe doesn’t have a Y-axis, use an eccentric bushing to correct eventual errors on the Y axis.
  5. Starting Point at Z-Axis: Start at least 10mm away from the workpiece on the Z-axis to allow for acceleration. If you start too close to the workpiece you’ll risk chipping the insert.
  6. Monitor Tool Wear: Regularly inspect the broach for signs of wear, such as chipping or dull cutting edges. Replace worn broaches promptly to maintain consistent keyway dimensions and prevent damage to the workpiece.
  7. Perform Regular Maintenance: Regularly clean and maintain the CNC lathe, broach, and tooling to ensure optimal performance and extend the service life of the equipment.

6. Troubleshooting Common Keyway Broaching Issues on CNC Lathes

When encountering issues during the keyway cutting process on CNC lathes, consider the following troubleshooting tips:

  • Inaccurate Keyway Dimensions: Check the broach geometry, CNC program, and alignment of the broach and workpiece. Make any necessary adjustments to ensure accurate keyway dimensions.
  • Excessive Tool Wear: Inspect the cutting parameters, broach material, and coolant application. Adjust these factors as needed to minimize tool wear and extend the broaching insert’s service life.
  • Poor Surface Finish: Evaluate the cutting parameters, broach geometry, and coolant application. Optimize these factors to improve the surface finish of the keyway.
  • Keyway not centered: Compensate for errors on the Y-axis. If your CNC lathe doesn’t have a Y-axis, use an appropriate eccentric bushing to correct errors on the Y axis.
  • Machine Vibrations: Check the broach holder, workpiece clamping, and machine leveling. Ensure that all components are secure and properly aligned to minimize vibrations during the machining process.

7. Conclusion

Embracing inserted keyway broaching tools on CNC lathes enables manufacturers to create internal slots and keyways with unmatched precision, efficiency, flexibility and cost-effectiveness. Additionally, the ability to complete the workpiece in a single setup offers enhanced flexibility in manufacturing. This makes it an excellent choice of tooling for manufacturing professionals to streamline their production process.

Keyway broaching on CNC lathes is optimal for a diverse range of workpieces composed of various materials from aluminium and steel to titanium. 

Keyway Broaching Slotting Cutter Workpiece Gisstec

Harnessing the power of keyway broaching on CNC lathes elevates the manufacturing process, using static broaching tools for smaller batches and high-speed broaching with live broaching units for serial production. 

To succeed in this, it’s important to select the right broaching tools, optimize the CNC lathe setup and programming, and follow best practices. This will enable manufacturers to achieve consistent and accurate keyway dimensions, ensuring constant high quality with reliable torque transmission between coupling components.

Contact Us for a Quote for Broaching Tools

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Angle Heads for CNC Machining Centers: The Ultimate Guide

Posted on by gisstec

Whether you’re machining on a 3 or 4-axis CNC machining center or a state-of-the-art 5-axis machining center, angle heads come to rescue for machining a variety of workpieces.   

In the world of CNC (Computer Numerical Control) machining, the addition of angle heads significantly streamlines the manufacturing process. Let’s take a straightforward, practical look at the different types of angle heads and how they’re used in everyday machining.

We’ll look into 6 common types of angle heads for machining centers:

  1. Right Angle Heads
  2. Adjustable Angle Heads
  3. Slim Angle Heads
  4. Double Output Angle Heads
  5. Heavy-Duty Angle Heads
  6. Modular Angle Heads

1. Right Angle Heads

A right angle head, as the name suggests, is positioned at a 90-degree angle. This handy design lets you work on the side surfaces of a piece without needing to move it around. 

Imagine you’re machining a workpiece on a 3-axis CNC machining center and want to drill holes into the sides. Without a right angle head, you’d have to rotate the workpiece for each side—quite a hassle, right? The right angle head lets you drill those holes easily, without all the fuss.

Whether you’re manufacturing parts for Benz or Airbus, it’s a popular angle head across various industries, from automotive to aerospace.

2. Adjustable Angle Heads

Sometimes, the machining task in hand requires more flexibility. Enter adjustable angle heads. With the ability to set them at any desired angle, these tilting heads are like the ‘Swiss Army knife’ of CNC machining. 

Take the aerospace industry, for example. The parts often have complex shapes that need precise machining at various angles. Adjustable angle heads are ideal for this task, providing the flexibility needed for such detailed work.

Angle Head Gisstec

Let’s say you’re machining a mold with a complex design—maybe it’s got a bunch of intricate curves and hard-to-reach corners. With a regular tool, you might have to move the workpiece around multiple times to reach all those spots. But with an adjustable angle head, you can just change the angle of the tool to reach those tricky spots without moving the workpiece.

Or maybe you’re making a mold for a large piece, but there’s a small, detailed area that needs precise machining. Again, the adjustable angle head comes to the rescue. It can be positioned just right to work on that small area without affecting the rest of the piece. It’s a bit like using a small spatula to spread frosting on a tiny corner of your cake without messing up the rest of it.

3. Slim Angle Heads

Ever tried to reach into a narrow, hard-to-reach space with a regular tool? It’s not the easiest task. Even the most advanced 5-axis CNC machining center will give up on you. Enter slim angle heads.

90º Slim angle heads are designed just for that—they have a thin, compact design that lets them access those tight spaces. It’s like when you want to tighten that screw but there isn’t enough space to go at it head on with a regular screwdriver. That’s when you start looking for that right angle screwdriver to save the day.

Angle Head Keyway Milling GS-11 Gisstec

In industries like mold and die making and aerospace, where drilling, tapping or detailed milling inside intricate cavities is needed, slim angle heads come into their own. 

These slim angle heads are used in the aerospace industry because aircraft components often require detailed work in confined spaces. Parts such as turbine blades, engine casings, and elements of the landing gear frequently have complex geometries or small features that require precise machining.

Let’s consider an engine casing. This component may also contain small features or holes that need precise machining. With a slim angle head, these spaces become accessible, ensuring each feature is crafted to the exact specifications.

4. Double Output Angle Heads

When it comes to mass production, speed is key. Double output angle heads speed things up by having two output spindles on opposing sides. This comes in handy when working on larger workpieces that have operations on either side.

Double Output Angle Head Gisstec

A double output angle head takes care of it without having to change the tool for the second operation. That streamlines the process and shortens the cycle time.

5. Heavy-Duty Angle Heads

Just like it sounds, heavy-duty angle heads are the heavy lifters of the bunch. They’re built to take on high loads and forces. This makes them perfect for big jobs involving a lot of milling, drilling, or tapping, removing considerably more material than its lighter counterparts. 

These heads have heavy duty conical bearings that are optimal for withstanding high forces and reducing vibrations. Think of shipbuilding or construction, where the pieces are large and the work is extensive—that’s where these angle heads shine. 

Heavy-Duty Angle Head Gisstec GT-FX

They also accelerate the job of emptying material inside a large mold in moldmaking industry, which can be a very time-consuming operation.

When you’re looking to remove a lot of material, drill large holes, tap big threads, this is your go-to angle head.

6. Modular Angle Heads

Imagine if you could mix and match parts of your angle head to suit different jobs. That’s precisely what modular angle heads offer. 

Their design lets you swap out different components depending on the job at hand. It’s a versatile choice that can save a lot of time and resources when dealing with diverse operations on a single workpiece.

It’s also an excellent way of swapping preset cutting tools quickly as a quick-change tool. This reduces the down-time of the machine used for adjusting the cutting tool.

Angle Heads and CNC Machining: How They’re Used in Different Industries

CNC (Computer Numerical Control) machining centers have become more versatile thanks to the addition of angle heads. These handy tools change the direction of the spindle, which lets us do work on multiple sides and axes without needing to move the piece. 

Now, we’ll be taking a look at how angle heads are used in various industries.

  1. Automotive Parts and Perpendicular Operations

Right angle heads are great for machining the sides of parts without having to flip them around. In the car industry, they’re often used for drilling and tapping operations on parts like engine blocks, gearbox housings, and suspension mounts.

  1. Aerospace Parts with Hard-to-Reach Spots

When making airplane parts, accuracy is key, and often the parts have complex shapes. That’s where adjustable angle heads come in—they can be set at any angle, which helps a lot in this industry. Slim angle heads come to rescue when you need to drill that oil passage hole inside a narrow bore with little clearance.

  1. Oil & Gas Parts and Deep Hole Drilling

Drilling deep holes into parts can be tricky, especially when the design of the part doesn’t give you much room to work with. That’s where long-reach angle heads are useful. They’re used in the oil and gas industry to drill precise holes in parts like downhole drilling tools, fracking equipment, and oilfield valves.

  1. Electronics Components Production

When making electronics parts in large volumes, speed and efficiency are essential. Multi-spindle angle heads can do multiple operations at the same time, like drilling and tapping. This helps speed up production, especially for things like consumer electronics casings or connectors.

  1. Molds, Dies, and Detailing

When you’re making molds and dies, often you have to work in tight, intricate spaces. That’s where slim-bodied angle heads come in handy. They can reach into these small areas and do precise milling operations.

  1. Jewelry and Art Pieces

For detailed work, like engraving on precious metals or custom art pieces, adjustable angle heads are the way to go. They can handle detailed work on irregular surfaces, ensuring high-quality results.

  1. Construction and Shipbuilding

For bigger jobs like construction and shipbuilding, you need large-sized angle heads that have a long reach. These heads make it easier to work on big surfaces like beams, hull plates, and large structural sections. They help cut down on the number of times you need to change the setup, which makes things more efficient.

  1. Medical Implants and Tools

In the medical industry, you need high precision when making things like implants and surgical tools. Adjustable angle heads are used here as well because they can handle the complex operations that are often needed.

Conclusion

As you can see, angle heads have a wide range of uses across different industries. Whether it’s a right angle head for side work, a slim angle head for narrow spaces, or a double output angle head for fast, high-volume jobs, each one has a part to play.

Knowing what each one can do helps you pick the right tool for your job, making your machining processes more efficient and hassle-free.

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Inserted Broaching Tools square

Top 7 Internal Keyway Cutting Methods: How To Choose the Right One

Posted on by gisstec

Keyways play a crucial role in mechanical systems, enabling power transmission between shafts and other machine elements. Cutting an internal keyway can be a challenging task, but with the right method and tools, it can be done with precision and efficiency. 

In this comprehensive guide, we will discuss seven popular internal keyway cutting methods. We will explore the advantages and limitations of each method, provide use case examples, and offer best practices to help you make an informed decision.

7 Methods for Cutting Internal Keyways

  1. Broaching
  2. Inserted broaching tools
  3. Driven broaching heads (Live broaching tools)
  4. Shaping / Slotting
  5. Keyseating
  6. Milling
  7. Wire-Cut EDM

1. Broaching

What you need

Machine: A Broaching machine
Tooling: Keyway Broaches

Introduction

Broaching is a widely used method for cutting internal keyways, involving the use of a broach—a specialized cutting tool with a series of progressively larger teeth. The broach is clamped on the broaching machine and either pulled or pushed through the workpiece to broach the keyway.

Broaching Machine

Advantages

  • High precision and accuracy: Broaching can cut keyways with tight tolerances and excellent repeatability.
  • Surface finish: The progressive cutting action of a broach results in a smooth surface finish.
  • Suitable for high-volume production: Broaching is a fast and efficient method, making it ideal for mass production.

Limitations

  • Expensive tooling and machinery: Broaching machines and custom broaches can be costly investments.
  • No blind holes: The broach has to go through the workpiece for this method.
  • The workpiece cannot be finished on one machine and needs to be reclamped. Because only the broaching operation can be done with this method.
  • Limited to certain material types: Broaching is generally suited to softer materials and may struggle with harder or more abrasive materials.
  • Less flexible due to custom tooling requirements: Broaches are designed for specific keyway geometries, making it difficult to accommodate design changes or multiple keyway profiles.

Use case examples

  • Automotive industry: Transmission gears and components, such as synchromesh assemblies.
  • Aerospace: Turbine engine components, including compressor and turbine disks.
  • Heavy machinery: Gearboxes, shaft couplings, and power transmission components.

Best practices

  • Ensure proper alignment of the broach and workpiece: Accurate alignment is crucial to avoid tool deflection and ensure consistent internal keyway dimensions.
  • Use the correct broach size and type for the desired keyway geometry: Selecting the appropriate broach will ensure optimal cutting performance and extend tool life.
  • Regularly inspect and maintain the broaching tool to prevent wear and damage: Keeping the cutting edges sharp and free of damage will improve cutting performance and extend tool life.

2. Keyway Cutting with Inserted Broaching Tools

What you need 

Machine: One of the following: CNC Lathe, CNC Machining Center, Slotter Machine (Slotting Machine), Shaping Machine, Conventional Lathe, Milling Machine

Tooling: Keyway Cutting Insert, Insert Holder

Introduction to Inserted Broaching Tools

Cutting keyways with inserted broaching tools is a modern broaching method, using a tool holder with replaceable cutting inserts. These keyway cutting tools can be used on CNC machines and a variety of other machines for slotting and shaping. This offers greater flexibility and reduced tooling costs compared to traditional broaching. 

Keyway cutting using this method on a CNC lathe or machining center eliminates the need to reclamp the tool on a separate machine in order to broach the keyway.

Inserted Broaching Tools Gisstec

In this method, first the workpiece is clamped in position. Then the keyway is cut by the tool through a series of successive passes. The tool removes an equal amount of material with each pass until the required size of the keyway is achieved. 

It’s also called static broaching tools since the Z-axis movement necessary for chip removal comes from the machine itself. On the other hand, a driven broaching unit generates the back-and-forth movement in Z-axis by itself. (See third method for details)

Advantages of Inserted Broaching Tools

  • One of the lowest cost methods for cutting an internal keyway while maintaining excellent precision: The use of replaceable inserts eliminates the need for expensive custom broaches or specialized machines.
  • Cuts keyways in blind holes: Allows for cutting keyways inside blind holes with or without a relief groove
  • Enhanced flexibility with interchangeable inserts: Multiple keyway profiles and tolerances can be machined using a single tool holder and a variety of cutting inserts.
  • Improved tool life and easier maintenance: Cutting inserts can be replaced when worn or damaged, extending the life of the tool holder and reducing maintenance costs.
  • Cutting inserts can have their lifespan extended by resharpening them multiple times, allowing for their reuse.
  • Works with a wide range of material types: Can be used to machine keyways in both soft and hard materials, including cast iron, steel, titanium and non-ferrous alloys.

Limitations

  • Slower process compared to traditional broaching: Multiple passes are required to create the keyway. So, it’s more efficient overall for small batches.
  • Less suitable for high-volume production: While inserted broaching tools offer greater flexibility, they are not as efficient as some of the other methods for large-scale production.

Use case examples

  • Small-scale production: Gears, pulleys, and other components requiring precise keyways.
  • Prototyping: Testing new keyway designs or validating component fit and function.
  • Repair and maintenance: Retrofitting existing components with new keyways or correcting worn or damaged keyways.

Best practices

  • Use the appropriate cutting insert for the material being machined: Different materials require specific cutting geometries and coatings for optimal performance and tool life.
  • Ensure proper tool holder alignment with the workpiece: Accurate alignment is essential to maintain consistent keyway dimensions and prevent tool deflection. Use appropriate tools to correct any axis errors.
  • Regularly inspect and replace worn cutting inserts: Timely replacement of cutting inserts will ensure optimal cutting performance, surface quality and extend tool life.

3. Keyway Cutting with Driven Broaching Heads

What you need

Machine: CNC Lathe with a C-axis or a CNC Machining Center
Tooling: Driven Broaching Unit

Introduction to Driven Broaching Tools

Driven broaching heads (live broaching units) are specialized tools that can be mounted on CNC lathes with C-axis or CNC milling machines. These driven tools convert the rotary motion from the turret/spindle to linear motion to drive an inserted broaching tool through the workpiece. 

Driven broaching tool NG-27 Gisstec

This high-speed broaching method is commonly used on CNC lathes. It creates keyways similarly to the second method, which utilizes static broaching tools. However, driven broaching tools are remarkably faster, exceeding the speed of static tools by over 10 times.

Advantages

  • Fastest method without a dedicated keyway cutting machine: It enables the finishing of the workpiece without unclamping and setting it up on a separate machine.
  • Enhanced flexibility: Driven broaching heads can be used with existing CNC equipment, eliminating the need for dedicated broaching machines.
  • Cuts keyways in blind holes: Allows for cutting internal keyways in blind holes
  • High precision and accuracy: Driven broaching heads can produce keyways with tight tolerances and excellent repeatability.
  • Excellent choice for medium to large production volumes: Combines the efficiency of dedicated broaching machines with the convenience of finishing the operation on the same machine, streamlining your production process.
  • Works with a wide range of material types: Can be used to machine keyways in both soft and hard materials, including cast iron, steel, titanium and non-ferrous alloys.
  • Some driven broaching heads come with advanced error correction features, which allows for quick troubleshooting.

Limitations

  • Although investing in a driven broaching tool can provide a rapid return on investment for larger production batches, it may not be the most cost-effective solution if you only occasionally require broaching operations.
  • The size of the workpiece is limited to the capacity of the CNC lathe being used.
  • Driven broaching heads have a limited stroke usually going up to around 65mm (~2.5”)
  • Maximum keyway width is limited depending on the material, but is generally not larger than 16mm (~5/8”)

Use case examples

  • Medium and large-scale production: Components such as gears, pulleys, and couplings requiring precise keyways.
  • Leveraging existing CNC machines: Manufacturers looking to expand their keyway cutting capabilities without investing in dedicated broaching machines.

Best practices

  • Use the correct broaching head and cutting tool for the desired keyway dimensions and material type: Selecting the appropriate tooling will ensure optimal cutting performance and extend tool life.
  • Ensure proper alignment of the driven broaching head and workpiece: Accurate alignment is crucial to avoid tool deflection and maintain consistent keyway dimensions.
  • Regularly inspect and maintain the cutting tool and broaching head to prevent wear and damage: Keeping the cutting edges sharp and free of damage will improve cutting performance and extend tool life.

4. Keyway Cutting by Shaping / Slotting

What you need

Machine: Shaping machine, Slotter/Slotting machine
Tools: Keyway cutting tools / Internal keyway cutter

Introduction to Shaping and Slotting

Shaping or slotting is a method that involves using a reciprocating single-point cutting tool to remove material and create the keyway. The cutting tool moves horizontally or vertically along the workpiece, gradually cutting the internal keyway with each pass.

Keyway Slotting Shaping Machine

The operation is performed on dedicated machines such as a shaper or a slotter. As for cutting tools, either integral keyway cutting tools or inserted broaching tools as in the second method can be used. An adapter might be necessary to clamp the tools depending on the machine type.

Advantages of Shaping / Slotting

  • Low tooling and machinery costs: Shaping machines and cutting tools are typically less expensive than dedicated broaching or keyseating equipment.
  • Simple setup and operation: The shaping process is straightforward, making it accessible to operators with varying levels of experience.
  • Cuts keyways in blind holes: Allows for cutting keyways inside blind holes
  • Works with a wide range of material types: Shaping can be used to machine keyways in both soft and hard materials, including cast iron, steel, and non-ferrous alloys.

Limitations

  • Limited precision and accuracy: Shaping may produce less accurate keyway dimensions and require more skill to achieve consistent results.
  • Slower cutting process: The reciprocating motion of the shaping tool can be less efficient than the continuous cutting action of a broach or the electrical discharge process of Wire-Cut EDM.
  • Poor surface finish compared to other methods: Shaping may produce rougher surface finishes, requiring secondary operations to achieve desired results.

Use case examples

  • General engineering: Pulleys, sprockets, and couplings used in a variety of industries and applications.
  • Low-volume production: Custom or unique components requiring keyways, where the expense of dedicated broaching or keyseating equipment is not justified.
  • Educational institutions: Training and teaching purposes, where students can learn fundamental machining techniques and principles.

Best practices

  • Use the appropriate shaping tool for the desired keyway dimensions: Selecting the correct cutting tool will ensure optimal performance and extend tool life.
  • Ensure proper alignment of the shaping tool and workpiece: Accurate alignment is essential for maintaining consistent keyway dimensions and preventing tool deflection.
  • Regularly inspect and maintain the cutting tool to prevent wear and damage: Keeping the cutting edges sharp and free of damage will improve cutting performance and extend tool life.

5. Milling Internal Keyways

What you need

Machine: CNC Machining Center, Milling Machine
Tooling: Angle head, cutting tool e.g. end mill

Introduction to Milling Keyways

Milling an internal keyway requires the cutting tool, e.g. an end mill to to cut at 90º along the bore length. This kind of operation will usually require an angle head to dive into the bore vertically. The keyway is machined by removing material with the rotating cutting tool which is clamped to the angle head.

Angle Head Keyway Milling GS-11 Gisstec

During the machining operation the lower body of the angle head needs to dive into the bore to cut the internal keyway. So this method is suited for workpieces with a bore large enough to accommodate the angle head.

This process can be performed on a variety of milling machines, including manual, CNC, and multi-axis machines.

Advantages of Milling an Internal Keyway

  • Suitable for a wide range of material types: Milling can machine keyways in soft and hard materials, including cast iron, steel, and non-ferrous alloys.
  • Can create keyways with varying depths and widths: Milling allows for greater control over keyway dimensions and can accommodate design changes more easily than dedicated broaching equipment.
  • Compatible with CNC machines for automated and precise keyway cutting: Milling can be integrated into CNC machining processes, offering improved accuracy, repeatability, and efficiency.
  • Can machine keyways in blind holes.

Limitations

  • Requires specialized tooling for internal keyways: Milling an internal keyway often requires an angle head. So it might be more suitable for higher-value or higher-volume milling parts in order to justify the investment.
  • Limited to certain keyway geometries: Milling may struggle with complex keyway profiles or non-standard shapes, particularly when using standard cutting tools.
  • Slower process compared to broaching: Milling can be less efficient than dedicated broaching machines, especially for high-volume production.

Use case examples

  • General engineering: Gears, sprockets, and couplings used in various industries and applications.
  • Automotive industry: Transmission components, such as gears and shafts, requiring precise keyways for power transmission.
  • Prototyping and small-scale production: Custom or unique components requiring keyways, where the flexibility of milling is advantageous over dedicated broaching equipment.

Best practices

  • Use the appropriate milling cutter for the desired keyway dimensions and material type: Selecting the correct cutting tool will ensure optimal performance and extend tool life.
  • Ensure proper alignment of the milling cutter and workpiece: Accurate alignment is essential for maintaining consistent keyway dimensions and preventing tool deflection.
  • Regularly inspect and maintain the cutting tool to prevent wear and damage: Keeping the cutting edges sharp and free of damage will improve cutting performance and extend tool life.

6. Keyseating

What you need

Machine: A Keyseating Machine
Tooling: Keyseater Tools / Internal keyway cutter

Keyseating is a method that uses a reciprocating cutting tool, called a keyseater or keyway cutter, to cut the keyway. The cutting tool is mounted vertically in the machine and moves up and down while the workpiece remains stationary.

Advantages of Keyseating

  • Low tooling and machinery costs: Keyseating machines and cutting tools are generally less expensive than dedicated broaching equipment.
  • Suitable for large workpieces and deep keyways: Keyseating machines can accommodate larger components and create deeper keyways than many other methods.
  • Works with a wide range of material types: Keyseating can be used to machine keyways in both soft and hard materials, including cast iron, steel, and non-ferrous alloys.

Limitations

  • Slower cutting process: The reciprocating motion of the keyseater tool can be less efficient than the continuous cutting action of a broach or the high-speed cutting of a driven broaching head.
  • Limited precision and surface finish: Keyseating may produce rougher surface finishes and less accurate keyway dimensions compared to broaching or Wire-Cut EDM.
  • Requires skilled operators: Achieving consistent results with keyseating requires experience and skill, particularly when working with harder materials or complex keyway profiles.

Use case examples

  • Large-scale components: Industrial gearboxes, couplings, and other power transmission elements in heavy machinery.
  • Shipbuilding: Propeller shaft keyways and components for marine propulsion systems.
  • Power generation: Turbine and generator shaft keyways in hydroelectric, nuclear, and fossil fuel power plants.

Best practices

  • Use the correct keyseater tool for the desired keyway dimensions: Selecting the appropriate cutting tool will ensure optimal performance and extend tool life.
  • Ensure proper alignment of the keyseater and workpiece: Accurate alignment is essential for maintaining consistent keyway dimensions and preventing tool deflection.
  • Regularly inspect and maintain the cutting tool to prevent wear and damage: Keeping the cutting edges sharp and free of damage will improve cutting performance and extend tool life.

7. Cutting Keyways with Wire-Cut EDM

What you need

Machine: Wire EDM

Introduction to Wire-Cut EDM Keyway Cutting

Wire-Cut EDM (Electrical Discharge Machining) is a process of cutting electrically conductive materials with high precision. It uses a thin, electrically charged wire to cut the required keyway by eroding material via electrical discharge. 

This process is highly accurate and can be used to machine intricate keyway profiles in conductive materials. In addition, it is particularly effective in cutting precise keyways when working with hard materials.

Advantages of Wire-Cut EDM

  • High precision and accuracy: Wire-Cut EDM can produce keyways with tight tolerances and excellent repeatability, making it ideal for high-precision applications.
  • No mechanical forces exerted on the workpiece: The non-contact cutting process eliminates the risk of tool deflection or workpiece distortion.
  • Can cut hard materials and complex geometries: Wire-Cut EDM can machine keyways in hardened materials, such as tool steels, and create intricate profiles that may be difficult or impossible with other methods.
  • Excellent surface finish: The controlled electrical discharge process results in a smooth surface finish, often eliminating the need for secondary operations.

Limitations

  • Slower process compared to other methods: Wire-Cut EDM can be time-consuming, particularly for deep keyways or large workpieces.
  • Higher operational costs: Wire-Cut EDM machines and consumables, such as wire and dielectric fluid, can be expensive.
  • Only suitable for electrically conductive materials: Non-conductive materials, such as ceramics or certain polymers, cannot be machined using Wire-Cut EDM.

Use case examples

  • Machining hardened materials: Tool and die manufacturing, where keyways must be cut in hardened materials or components.
  • Complex geometries: Intricate keyway profiles and shapes, such as non-standard or curved keyways, that cannot be machined using conventional methods.

Best practices

  • Use the appropriate wire type and size for the material being machined: Wire selection is critical to achieving optimal cutting performance and minimizing wire breakage or wear.
  • Ensure proper alignment of the wire and workpiece: Accurate alignment is essential to maintain consistent keyway dimensions and prevent wire deflection.
  • Regularly maintain and clean the Wire-Cut EDM machine to ensure optimal performance: Timely maintenance, such as replacing worn wire guides or cleaning the dielectric fluid system, is crucial to the overall efficiency and longevity of the machine.

Conclusion

Cutting internal keyways is an essential task in many industries, and selecting the most appropriate method for a particular application is critical to achieving the desired results efficiently. 

Broaching, keyway cutting with inserted broaching tools, keyseating, Wire-Cut EDM, shaping, milling, and keyway cutting with driven broaching heads each offer unique advantages and limitations. 

The ultimate choice will depend on the size and geometry of the workpiece, keyway dimensions and quantity. By understanding these factors and applying best practices, manufacturers can make informed decisions and optimize their keyway cutting processes to maximize efficiency, precision, and overall performance.

Get a Quote for Broaching Tools

Everything You Need to Know About Broaching

Posted on by gisstec

Broaching on CNC Lathes and Machining Centers

Broaching (Slotting) is a machining process in which a keyway or a profile is created by cutting movements on the Z-axis. The cutting depth is determined with movements of the X-axis. With the working stroke on the Z-axis, material is removed depending on the cutting depth. The return movement is an idle stroke where no material is removed because there is only one cutting direction.

Passfedernut und Keilwelle erstellt mit Stoßtechnik
Keyway and Spline Profiles made with Broaching on CNC

Kerbverzahnung und Spiral erstellt auf CNC-Drehmaschine
Spline and Spiral profiles made on a CNC Lathe

Broaching operations can be done on CNC milling and lathes as well as on broaching machines, whereby most CNC applications occur on lathes, since the workpiece can be finished without re-clamping. The C-axis is required for polygon profiles such as square, hexagonal, serrations and splined shafts. To open a single keyway, only the Z and X axes are usually sufficient. It is important that the lathe’s chuck can be locked, as the chuck must remain fixed while the keyway is being machined.

Innenvierkant und Innensechskant Profile erstellt mit Stoßverfahren
Square and Hexagon profiles made with broaching operation

Static and Live Broaching Tools

There are static as well as driven tool solutions. The right choice depends primarily on the number of keyways / edges / teeth and workpieces per month. With a smaller number of workpieces up to around a few thousand pieces per month, the static slotting tools are very cost-effective. However, if the number of pieces is over several thousand per month, a live broaching tool is faster and economically the better solution.

Statische Nutstoßwerkzeuge: Stoßplatten und Plattenhalter
Static slot cutting tools: inserts, insert holders and eccentric bushing for adjusting the Y-axis 

Static broaching solutions, which are widely used, consist of broaching (slotting) tools with a cylindrical clamping option and inserts in various geometries, sizes and tolerances. This technique has two components: the insert and the insert holder. The insert is attached to the insert holder with a screw. The insert holder, usually with a shaft diameter of 25 mm or 32 mm, is then clamped to a boring bar holder or a VDI boring bar holder with a corresponding diameter on the CNC lathe. For use on machining centers, the holder can be clamped with any tool holder with a cylindrical holder, such as a collet chuck or Weldon holder which you can easily supply from your local vendor.

By pushing the insert into the workpiece, the keyway is machined step by step. The cutting speed and the cutting depth must be set depending on the workpiece material. Experience shows here that catalog values mostly only serve as approximate values and that values adapted to various factors on site (room temperature, machine type, machine condition, workpiece quality, coolant, etc.) can produce optimal machining results.

Außenverzahnung mit Angetriebenes Stoßgerät auf CNC-Drehmaschine mit C-Achse.
External gear with live broaching tool on CNC lathe with C-axis.

The question that often arises here is whether broaching does not place too much stress on the turret or spindle of the CNC machine. The load that is exerted on the CNC lathe or machining center is comparable to that of a drilling operation. Larger sizes can be machined in two steps first using a smaller insert, then the actual size.

A Y-axis is not necessary for applications on lathes. However, if the lathe does not have a Y-axis, an eccentric bushing is necessary to correct the errors on the theoretical Y-axis of the turret. Over time, there is usually a play in the Y-axis on lathes and so that the grooves are exactly in the middle, this error must be corrected with an eccentric bushing. The C-axis is absolutely necessary for square, hexagonal and gear machining, as all edges or teeth are machined individually.

Comparison of static broaching tools vs live broaching tools:

Static Broaching Tool Live Broaching Tool
Speed ✖ ✔
No Load on the turret ✖ ✔
Efficient with higher quantities ✖ ✔
Efficient with lower quantities ✔ ✖
Usage without C-Axis ✔ ✖
Machining length over 65mm ✔ ✖
Usage on machining centers ✔ ✖
Keyway, square, hexagon and spline profile machining ✔ ✔

Live broaching tools are worthwhile for large quantities and provide the following advantages in the long term:

  • Cost-efficient production of different geometries
  • Resource-saving production and protection of the lathe turret
  • Low investment costs compared to purchasing a separate broaching machine
  • Fast processing. Up to 400-800 strokes per minute


Example application of the live broaching tool on a lathe with C-axis

Slot Broaching or Rotary Broaching?

For internal square, internal hexagon and internal gear machining, an alternative method is the rotary broaching process. Rotating broaching tools are relatively fast because the entire profile is machined at once and not all edges individually, as is the case with slot broaching.

Räumwerkzeug - Innensechskant
Rotary Broaching Tool – Hexagon Profile

Broaching tools can also be used flexibly on lathes and machining centers. Since processing only has to take place in one pass, the stress on the machine is very high. The machine can often come to a standstill, especially with larger diameters. Process reliability is therefore not guaranteed, especially with larger diameters and materials with higher hardness levels.

With broaching tools, machining can be done in as many passes as necessary. This guarantees process reliability, as the machining parameters can be adjusted depending on the material and profile size.

Comparison: Slot Broaching vs Rotary Broaching

Slot Broaching Rotary Broaching
Process reliability ✔ ✖
Less load on the machine tool ✔ ✖
Machining in multiple passes ✔ ✖
Relatively lower price ✔ ✖
Machining length over 70mm ✔ ✖
Machining diameter over 20mm ✔ ✖
High precision ✔ ✖
Keyway profile ✔ ✖
Square, Hexagon, Spline profile ✔ ✔
Usage on CNC lathe and machining centers ✔ ✔
Speed ✖ ✔
Open Polygonal profiles without C-Axis ✖ ✔

What should you consider when selecting inserts and insert holders?

There are no standard interfaces for inserts and insert holders. This is why vendors of broaching tools usually have a system with their own interfaces and the inserts are usually not interchangeable.

One of the most important technical points to consider when it comes to inserts is the material inserts are made of. Carbide is not suitable for broaching because its low breakage strength does not guarantee process reliability. You can make 100 keyways with a carbide insert, but the edges might break off after a few machining operations. In addition, the surface quality of your keyway might start deteriorating as early as after opening a dozen keyways.

HSS Insert TIN-Coated – Spline Profile

In the manufacture of inserts, preference must be given to materials with high wear resistance and high compressive strength, e.g. powder metallurgical HSS alloys with resistant elements. Inserts made of suitable HSS alloys have a longer life due to the wear resistance and offer much greater process reliability thanks to the high pressure resistance.

With a TIN coating, the wear resistance and life of inserts can be increased. The geometry of the panels is also an important technical point that influences the surface quality, among other things. TiAlN coating may be prefered when machining harder materials.

Comparison: Sintered HSS-Alloy Insert vs Carbide Insert for Broaching

Sintered HSS-Alloy Carbide
Process Reliability ✔ ✖
Wear Resistance ✔ ✖
Pressure Resistance ✔ ✖
Useful Life ✔ ✖
Constant Surface Quality ✔ ✖
Resharpening possibility ✔ ✔
Relatively lower price ✖ ✔

For the commercial aspects, particular attention should be paid to the size, tolerance and availability selection. If there are several common tolerances to choose from and are available as catalog goods, the procurement costs are lower in contrast to special plates on request. When machining keyways, tolerances H7, JS9, P6 and C11 are the most common.

Nutenstoßwerkzeug - Plattenhalter
Slotting Tool – Insert Holder

With insert holders, stability is of the utmost importance, as better stability for a longer service life of the inserts and better surface quality. With the holder, a longer shaft contributes to the stability, with a larger contact surface and, if necessary, fastening with two screws instead of one screw. A continuous substructure behind the insert seat ensures vibration damping and thus also increases the stability of the holder. Short insert seat protection must be avoided for optimal surface and service life of the insert.

Coolant supply through the holder ensures removal of the chips, a better surface and protection of the cutting edge.

Gisstec Schwenkkopf – GT-FX

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Gisstec Verstellbarer Winkelkopf – GT-FX

+/- 90º Verstellbarer Schwenkkopf

SK40/SK50 Ausführung. Verwendbar mit beliebigen SK40/SK50 Werkzeugaufnahmen.

Direkte Flanschverbindung an Maschinenspindel. Höchste Stabilität.

Drehzahl: 3.500 U/min

Drehmoment: 210 Nm

360º Verstellbar um die eigene Achse

Gisstec Winkelkopf - GT-FX

Winkelkopf Anfrage

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Vielen Dank für Ihre Anfrage für Gisstec Winkelköpfe.

Wir bearbeiten Ihre Anfrage und melden uns umgehend bei Ihnen zurück.

Gisstec GmbH
Technischer Vertrieb

Möchten Sie 10x schneller nutstoßen auf Ihrer Drehmaschine mit C-Achse?

Sehen Sie wie Sie 10x schneller nutstoßen können mit dem präzisten angetriebenen Nutstoßgerät.

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Kein Problem. Benutzen Sie die innovativste und präziste Nutstoßwerkzeuge und erhöhen Sie Ihre Produktivität.

Nutstoßen einfach und präzis mit Gisstec Nutstoßwerkzeugen.

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Nutstoßen in 10 Sekunden – Gisstec Stoßgerät

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Nutstoßen in 10 Sekunden mit Gisstec Stoßgerät auf CNC-Drechmaschine

Nutstoßen, Keilwelle, Vierkant, Sechskant, Kerbverzahnung Stoßen innerhalb wenigen Sekunden. Angetriebenes Stoßgerät von Gisstec für CNC-Drehmaschinen mit C-Achse

Korrigieren Sie einfach die Parallelität und bleiben Sie immer innerhalb Toleranzen

 

Nutstoßen Vergleich – Gisstec, Horn, Simtek, Dümmel

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Wer bietet die besten Nutstoßwerkzeuge? Gisstec, Horn, Simtek oder Dümmel?

Wir testen Nutstoßwerkzeuge mit Nutenbreite 6mm von Gisstec, Horn, Simtek und Dümmel.

Es werden folgende Werte getestet:

  • Oberflächenqualität
  • Lebensdauer
  • Parallelität

Es werden auch folgende marktrelevante Werte verglichen:

  • Auswahl Standardgrößen für Platten
  • Auswahl Standardgrößen für Halter
  • Auswahl Standardprofile
  • Lieferfähigkeit Sonderprofile
  • Qualität von Infomaterial

Wir teilen die Ergebnisse dieses Nutstoßen-Tests mit Gisstec, Horn, Simtek und Dümmel Werkzeugen bald auf dieser Seite mit.