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A machine taper is essential for ensuring accuracy in machining by precisely connecting cutting tools to a machine’s spindle.

In this guide, you’ll learn how tapers function across different machines, their indispensable role in tool security and alignment, and their varied forms and uses.

Whether you’re selecting the right taper for your equipment or understanding its maintenance, this article offers a deep dive into everything machine taper-related.

Key Takeaways

  • Machine tapers, like Morse, Jacobs, and HSK tapers, are crucial components in machinery used to secure tools, ensure precision, and reduce vibration in machining operations.
  • Tapers are available in various sizes and shapes to meet the needs of different applications, and they require precise measurement and regular maintenance to ensure optimal performance.
  • When selecting a taper, it’s important to consider the taper’s type, size, and specific application requirements to ensure compatibility and enhance the efficiency and quality of machining processes.

Understanding Machine Tapers

Machine tapers are the unsung heroes in the machinery world. They serve a multitude of purposes in a variety of machinery, including:

  • Securing cutting tools
  • Ensuring precision in machining
  • Facilitating quick tool changes
  • Providing stability and rigidity to the machine
  • Allowing for efficient power transmission
  • Reducing vibration and chatter during operation

These tapers are essentially uniform reductions in the cross-section or diameter of a part, which often result in a conical shape. They play a crucial role in the functionality and performance of machines, from handheld drills to milling machines.

Purpose of Machine Tapers

The design of machine tapers allows for the secure holding of tool holders and cutting tools to a machine’s spindle head, a factor crucial for precise machining operations. Morse tapers, for instance, utilize friction to hold shanks in place within the socket, contributing significantly to precision and repeatability during tool changes in machine tools.

Types of Machine Tapers

A variety of machine tapers, including:

  • Morse
  • Jacobs
  • Jarno
  • Brown & Sharpe
  • HSK
  • and others

cater to diverse machining needs in the expansive world of machinery. Each type of taper has its unique application and specifications. For instance, BT tapers are used in machining centers and heavy-duty milling applications and are available in eight dimensions.

HSK tapers, with their 1.20 inch-per-foot taper ratio, are employed in a wide range of machining applications from lathes to grinding and are available in multiple configurations. In contrast, NMTB tapers, characterized by a flange and keyways design with a 3.50 inches per foot taper ratio, are intended for heavy-duty use in NMTB spindles. The tapered shank design of both HSK and NMTB tapers ensures secure and precise tool holding in a tapered spindle.

R8 tapers, also known as M1TR tapers, were crafted by Bridgeport Machines, Inc. for milling machine applications and are held in place using a drawbar. The Jarno taper, with a modest 0.60 inch-per-foot ratio, is typically found in lathe headstocks, tailstocks, and certain milling and profiling machines.

Morse Tapers: A Closer Look

A deeper exploration into the realm of tapers reveals Morse tapers, named after Stephen A. Morse. Developed in the mid-1860s, these tapers were designed for the swift and easy changing of tools within machines. Morse tapers are characterized by a typical angle of 1.49°, a key specification for identification and fitting into machine heads.

These tapers are often deployed in securing reamers, drill bits, mill holders, collets, and lathe centers.

Morse Taper Sizes and Dimensions

Morse tapers present us with a range of dimensions. For example, a Morse taper #2 has a large end dimension of 0.7000 inches, a small end of 0.5720 inches, and a length of 2.56 inches.

The Morse taper #3 measures 0.9380 inches at the large end, 0.7780 inches at the small end, with a length of 3.19 inches.

At the higher end of the spectrum, Morse taper #7 is one of the largest, with morse taper dimensions of a 3.2700 inch large end, a 2.7500 inch small end, and a 10.00 inch length. This morse taper shank size is commonly used in heavy-duty applications, and it’s worth noting that morse taper varies across different sizes and applications.

Common Uses of Morse Tapers

In various industrial machines, Morse tapers serve a significant role as tapered spindles or shanks. They are typically found in industrial drill presses, where they are frequently used in the spindles to secure tools. Additionally, Morse tapers are commonly used in lathe tailstocks, as well as with taper-shank twist drills and machine reamers, offering self-holding capabilities and, when needed, they can be modified for use with a drawbar.

Jacobs Tapers: Features and Applications

A Jacobs taper for holding a drill chuck on a CAT taper toolholder…

Next, we focus on Jacobs tapers, which boast a unique design. Known for their self-holding feature, they can be used for light-duty applications without the need for a drawbar. Specifically designed to securely attach drill chucks to arbors, they enhance the precision of drilling operations.

These tapers are polished smooth to keep the tapers clean and dry, thereby preserving the necessary friction for their self-holding characteristic.

Jacobs Taper Sizes and Dimensions

Jacobs tapers come in a variety of sizes including:

  • #0 taper: small end – 5.80 mm, large end – 6.35 mm, length – 11.11 mm
  • #1 taper: small end – ?, large end – ?, length – ?
  • #2 taper: small end – ?, large end – ?, length – ?
  • #2 Short taper: small end – ?, large end – ?, length – ?
  • #2½ taper: small end – ?, large end – ?, length – ?
  • #3 taper: small end – ?, large end – ?, length – ?
  • #4 taper: small end – ?, large end – ?, length – ?
  • #5 taper: small end – 33.43 mm, large end – 35.89 mm, length – 47.63 mm
  • #6 taper: small end – ?, large end – ?, length – ?
  • #33 taper: small end – ?, large end – ?, length – ?

Please note that the missing measurements are not provided in the original text.

Securing Drill Press Chucks with Jacobs Tapers

Jacobs tapers are pivotal in securely attaching a drill chuck to an arbor. They are designed to secure drill press chucks in drill presses, handheld drills, and lathes for accurate operations.

The self-holding design of Jacobs tapers, a versatile tool mounting system, eliminates the need for a drawbar and varies by size, making them suitable for light-duty applications such as securing drill chucks to arbors.

Jarno Tapers

Jarno Taper on a lathe center…

Named after Brown and Sharpe Manufacturing, Jarno tapers are characterized by their 0.60 inches per foot taper ratio. Often found in lathe machinery, they serve as headstock and tailstock spindles, and are also employed in profiling and die-sinking machines.

There are 19 standard sizes of Jarno tapers, with the larger diameter ranging from 0.25 to 2.50 inches and the smaller diameter from 0.20 to 2.00 inches.

Brown and Sharpe

Brown and Sharpe taper on a collet chuck…

Much like Jarno tapers, Brown and Sharpe tapers come in a range of sizes, with the large end diameters starting as small as 0.250 inches and reaching up to 3.4271 inches for the largest size. The taper per foot for the Brown and Sharpe tapers varies, with some sizes having a taper per foot of 0.6000 inches, while others have different measurements such as 0.6246 or 0.5010 inches.

Older tooling machines, such as those used for drill bits, reamers, end mill holders, and collets, commonly utilize these tapers. Machine tool spindles are most commonly found in these types of machinery.

HSK Taper

Next, we discuss HSK tapers, which are specifically designed for metal and wood milling. Featuring a hollow shank, they are specifically created for high-speed machining applications. The HSK taper has a 10:1 ratio and is standardized as:

  • ISO 12164
  • DIN 69893
  • DIN 29893-1
  • DIN 69063-1

Unlike traditional tool holders with retention knobs, HSK tool holders lack this feature and rely on high precision balancing, often requiring specific equipment for operations with exceptionally high rotation speeds.

NMTB Taper

The creation of the NMTB taper standard in 1927 is credited to the National Machine Tool Builders’ Association (NMTB). This standard has been influential in the machine tool industry. The NMTB taper has the following features:

  • Taper ratio of 3.50 inches per foot
  • Designed specifically for use in NMTB spindles
  • Includes a single flange with two keyways
  • Typically used for heavy-duty applications.

A drawbar is utilized to secure the tapered shank tightly in the tool shank of power tool spindles of equipment using NMTB taper.

R8 Taper

Another type worth exploring is the R8 taper. Specified as 3.5 inches per foot, they are often associated with Bridgeport Machines, Inc., for milling machine applications. The correct angular conversion for an R8 taper from inches per foot is approximately 16.26 degrees.

CAT, CV, or V-flange taper

CAT, CV, or V-flange tapers are also worthy of attention. These tapers, also known as:

  • ANSI B5.50
  • Caterpillar “V-Flange” standard
  • ISO 7388-1
  • IS 11173 (TC)
  • DIN 69871
  • NFE 62540

are considered interchangeable with ANSI (Caterpillar) shanks.

Measuring Tapers: Tools and Techniques

Having explored the various types of tapers, it’s time to understand how they are measured. The measurement of tapers is integral to ensure their proper fit and function. Tools such as calipers and indicating 2-point gauges are commonly used for this task.

An easy way to measure the taper angle is to use ball gages.

Essential Measuring Tools

A 0.0001” Dial Indicator is a vital tool for verifying the spindle taper’s exactness. Non-drying high-spot paste can be used to detect imperfections in the taper contact surface.

Precision test bars are employed to ensure the taper is correctly dimensioned and aligned within the machinery.  Here is a typical CAT 40 Test Bar:

It is essentially a cylindrical standard attached to a tool holder.

Taper Maintenance and Cleaning

Similar to other components, machine tapers also necessitate regular maintenance and cleaning for ensuring optimal performance and longevity. Failure to maintain and clean tool tapers can lead to precision issues in machining and diminish both the cutting tools’ and the spindle’s service life.

Importance of Taper Maintenance

Routine maintenance of machine tapers is crucial to maintain optimal cutting performance. Here are some steps to follow:

  1. Perform monthly inspections of the taper surface.
  2. Clean the taper surface regularly to remove any dirt or debris.
  3. Apply oil to the taper surface to ensure smooth operation.
  4. If a taper surface is damaged, use a finish reamer to clean it and enhance contact and accuracy.

By following these steps, you can ensure that your machine tapers are in good condition and performing at their best.

Here is our article on spindle taper maintenance.

Cleaning Methods and Tools

Kelch Taper Cleaner…

An effective cleaning system for tool tapers involves using a specialized taper cleaning tool, which includes a drive unit with a brush and compressed air nozzles to clean automatically. Tapered brass brushes are recommended for cleaning tapers without causing damage.

For heavy surface corrosion on tapers, a wire wheel on a Dremel and WD-40 can be effectively utilized.

Selecting the Right Taper for Your Application

Given the variety of tapers available, choosing the right one can pose a challenge. The right taper can significantly affect the efficiency of the machinery and the quality of the final product.

Factors to Consider

Several factors should be considered when choosing a taper. The type or style of the taper, like CAT, BT, or HSK, and its size must be selected based on the specific application, considering the different advantages they offer.

The particular industries and applications, including aerospace, automotive, and construction, should dictate the taper selection to ensure compatibility and performance.

Tips for Choosing the Right Taper

To ensure proper fit and function, it’s vital to match the taper with both the machinery and the tooling. It is crucial to determine whether the taper should be self-releasing for ease of tool change or self-holding to ensure a more secure fit, depending on the specific machining operation.


Diving deep into the world of machine tapers, we’ve explored the various types, their dimensions, uses, and the integral role they play in machinery. From Morse to Jarno, each taper has unique characteristics that cater to specific applications, ensuring optimal performance and longevity. Regular maintenance and proper cleaning practices are critical to prevent precision issues in machining and to extend both the cutting tools’ and the spindle’s service life. Choosing the right taper can significantly influence the efficiency of your machinery and the quality of your final product.

Frequently Asked Questions

tapers are measured using tools such as calipers, indicating 2-point gauges, and ball gages.

Maintenance and cleaning are important for tapers to prevent precision issues in machining and prolong the service life of cutting tools and spindles.  Failure to do so can lead to various problems.

Not all machines accept all taper types (usually they accept just 1 taper type), so it is important to check the specifications of your equipment before choosing a taper.


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