Introduction to Keyway Broaches
A keyway broach is a cutting tool used to cut keyways into parts or shafts. Keyways are rectangular or square slots that allow keys to be inserted for transmitting torque, connecting parts, or preventing relative motion between two machine elements.
What is a Keyway?
A keyway is a precision slot or groove machined into a shaft or part. The keyway receives a woodruff key, spline key, feather key or other rectangular keys to provide a solid connection between two components while still allowing axial movement.
Benefits of Keyway Broaches
- Accurate and consistent production of keyways
- Ability to broach internal and external keyways
- Single pass broaching saves time versus milling or shaping
- Provides strong interference fit between key and keyway
- Available in a range of sizes for different applications
Types of Keyway Broaches
There are two main types of keyway broaches:
Solid Keyway Broaches
Solid keyway broaches are made from a single piece of high speed or carbon steel. They are capable of broaching in both directions (push and pull). Solid broaches are best for short runs and intermittent broaching operations.
Built-Up Keyway Broaches
Built-up broaches are constructed by stacking and welding individual thin sections together. This allows each tooth to be sharpened independently. Built-up broaches are made for high volume, continuous broaching on CNC machines.
| Broach Type | Advantages | Disadvantages |
|---|---|---|
| Solid | Lower cost, bidirectional cutting | Entire broach must be sharpened |
| Built-up | Teeth sharpened individually | Higher cost, unidirectional cutting |
The most suitable keyway broach depends on factors like run quantity, workpiece materials, and precision requirements.
Common Uses and Applications of Keyway Broaches
Keyway broaches are commonly used in many industrial applications that require the machining of keyways into shafts, gears, pulleys, couplings, sprockets, and other mechanical parts.
Power Transmission
One of the most common uses of keyways is in power transmission applications. The keyway allows a robust connection between shafts and mating components like gears, pulleys, or sprockets while still permitting axial movement and adjustment:
- Gear drives
- Chain and belt drives
- Couplings
- Camshafts
- Drive shafts
The keyway broach cuts an accurate, clean keyway that securely positions the key for reliable torque transmission.
Machinery Construction
Keyways broached into shafts are also important for assembling machinery where affixing gears, bearings, collars, and other components to shafts is required:
- Machine tools - lathes, mills, drills, etc.
- Printing presses
- Textile equipment
- Robotics
- Conveyor systems
Keyways provide solid rotational fixation while enabling linear adjustment of attached parts.
Automotive Applications
Keyway broaches are indispensible for manufacturing keyways in parts like:
- Camshafts
- Crankshafts
- Gear shafts
- Steering columns
- Axle shafts
Precision broached keyways result in smoother engine performance and greater reliability.
Whether the need is for power transmission, mechanical construction, or automotive manufacturing, keyway broaches provide an efficient method for producing high-quality keyway slots and grooves.
Key Features and Benefits of Keyway Broaches
Keyway broaches offer distinct features that provide major benefits compared to other keyway cutting methods.
Precise Dimensions
Keyway broaches cut very accurate slots with tight tolerances. This ensures:
- Consistent fit with keys
- Smooth power transmission
- No vibration or play
For example, a standard Woodruff keyway broach will hold dimensions within +0.0005/-0.0000 inches.
Superior Finish
The broaching action produces an excellent surface finish in the keyway. Benefits include:
- Reduced stress concentrations
- Increased fatigue strength
- Smoother key engagement
Typical keyway surface finishes are 8-32 microinches Ra, reducing friction and wear.
Faster than Milling or Shaping
Broaches cut keyways in one pass, saving significant production time over multi-pass milling or shaping operations. For example, broaching a 1" x 1/4" keyway takes just 30 seconds versus 2-3 minutes for milling.
Internal and External Capabilities
Keyway broaches can cut both internal and external keyways in parts. This allows flexibility in design not possible with milling/shaping.
Range of Sizes
Keyway broaches are available in a wide range of standard and custom sizes from just a few mm to over 25mm. This covers most applications.
Hardened Materials
Keyway broaches can cut keyways in hardened materials up to RC 45-50. Milling and shaping cannot match this capability.
With their precision, speed, versatility, and hardened material cutting ability, keyway broaches are an indispensable production tool for keyway cutting operations.
How to Select the Right Keyway Broach
Choosing the optimal keyway broach requires considering factors like the keyway design, workpiece material, precision needs, and production volume.
Keyway Design
The keyway broach must match the desired keyway profile. Common options include:
- Standard parallel keyways for feather keys or Woodruff keys
- Spline keyways
- Involute or serrated keyways
- Custom shapes
Broaches for standard keyway designs like ASA, DIN, ISO, or SAE are readily available. For special shapes, a custom broach will need to be manufactured.
Workpiece Material
The broach must be harder than the workpiece material to cut efficiently. Considerations when selecting material include:
- Carbon steel broaches for most low/medium carbon steels
- HSS broaches for hardened steels up to RC 45-50
- Coated carbide for very hard or abrasive alloys
The broach material should also have good impact strength for durability.
Precision Requirements
Keyway broach precision ranges from +/- 0.005 in down to under +/- 0.0005 in. Tighter tolerances require more care in broach selection and process control.
Production Volume
For low to medium volumes, solid broaches are a good economical choice. For high production, built-up broaches are recommended for their longevity and repairability.
Pilot broaches may also be used for precisely sizing the keyway in preparation for a larger finishing broach.
Consulting keyway broach size charts and manufacturers' recommendations can help guide the optimal broach selection for a given application.
Benefits of Amazon Prime for Buying Keyway Broaches
Amazon Prime provides several advantages when purchasing keyway broaches and other metalworking tools.
Fast Free Shipping
Amazon Prime members qualify for free two-day shipping on millions of Prime eligible items. This provides faster delivery times versus standard shipping methods when ordering keyway broaches.
For shops that need replacement broaches quickly to avoid downtime on a keyway broaching machine, the fast free Prime shipping can be a lifesaver.
Free Returns
Amazon Prime simplifies the returns process by providing free returns on most items. This makes it easy to exchange keyway broaches if the wrong size or type was accidentally ordered.
The ability to return machining tools like broaches at no cost eliminates risk if the item doesn't meet expectations.
Amazon Prime Savings
Prime members get exclusive access to special discounts and savings on select items. This includes savings on industrial supplies like keyway broaches.
Amazon frequently marks down prices on best-selling keyway broaches, allowing Prime members to take advantage of the extra savings.
The fast free shipping, easy returns, and exclusive discounts make Amazon Prime a valuable membership for shops purchasing keyway broaches and other metalworking equipment online.
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Discover The Benefits Of Using Keyway Broaches For Your Cutting Needs
Keyway broaching is a highly efficient process that can achieve finished metal products by machining shapes, including non-standard shapes such as splines, keyways, and non-circular holes, in one pass. The benefits of keyway broaching include high production rates, repeatability, and the ability to complete both the rough cut and the finished cut with a single pass of the machine. Keyway broaching on CNC lathes offers flexibility, precision, repeatability, reduced setup time, and reduced logistics efforts. Keyway broaching allows for precise control over the dimensions of the keyway, resulting in a high degree of accuracy. Keyway broaches are renowned for their precision machining capabilities, making them indispensable in various industrial and scientific sectors. Keyway cutting with a broaching machine is similar to keyseating, but offers greater flexibility and reduced force. Broaching a long keyway is possible with broaches that were not designed for it, but the only benefit would be reduced force.
What Are The Disadvantages Of Using Keyway Broaches?
There are some disadvantages to using keyway broaches, including:
- Risk of tipping: If the bushing is too short in relation to the bore length of the item being broached, there is a risk of tipping of the broach.
- Need for a press: Machine tools such as lathes and mills are not presses, which are needed to force a broach through metal. Attempting to use a machine tool for broaching can result in damage to the tool and the workpiece.
- Difficulty with blind keyways: Broaching a blind keyway can be challenging, as the toolpaths get wider and wider as the tool comes out of the hole.
- Specialization: Each broach is specialized to cut just one shape, so either the broach must be specially designed for the geometry of the workpiece or the workpiece must be designed around a standard broach geometry.
- Harder materials: Broaching is more difficult on harder materials, such as stainless steel and titanium, but is still possible.
