Acme threads are a type of screw thread with a trapezoidal profile, offering advantages in power transmission applications. They are known for their strength and ability to handle significant loads, commonly used in machinery where linear motion is required. These threads have a 29-degree thread angle, and their dimensions are defined by standards such as ASME/ANSI B1.5.
What are Acme Threads?
Acme threads are screw thread profiles characterized by their trapezoidal shape, widely used in applications requiring high load capacity and precision linear motion. They feature a 29-degree thread angle, unlike the sharper V-threads. These threads are designed for smooth and efficient power transmission, commonly found in lead screws, vises, and other machinery. The profile allows for robust performance and reduced friction compared to square threads, making them suitable for heavy-duty applications. Acme threads come in various classes, each providing specific clearances for different functional requirements.

Acme Thread Types
Acme threads are categorized into general purpose, centralizing, and stub types. These variations cater to different application needs, affecting factors like fit and the intended use in various mechanisms.
General Purpose Acme Threads
General purpose Acme threads, as defined by ANSI B1;5, are designed with clearances on all diameters for free movement. These threads are commonly used in applications where the internal thread is fixed, and the external thread moves, guided by bearings. The three classes, 2G, 3G, and 4G, offer varying levels of precision and clearance. These threads are widely applied due to their versatility and ease of use in many mechanical systems.
Centralizing Acme Threads
Centralizing Acme threads are designed to align the screw and nut accurately. They are used in applications requiring precise axial movement with minimal play. While less common than general-purpose threads, they provide superior alignment and are often preferred in situations needing high accuracy. These threads maintain consistent positioning and reduce the chance of errors or jamming, making them suitable for specialized machinery. Their dimensions and tolerances are detailed in relevant standards.
Stub Acme Threads
Stub Acme threads feature a shorter thread height compared to standard Acme threads, making them ideal for space-constrained applications. These threads maintain the 29-degree thread angle but offer a reduced thread depth, allowing for a more compact design. They are commonly used in situations where a lower profile is necessary and still require a good load-bearing capacity. The fit of Stub Acme threads corresponds to Class 2G, offering a balance of precision and clearance. They are standardized by ASTM B1.8.
Acme Thread Standards
Acme threads are governed by industry standards to ensure interchangeability and proper function. These standards, such as ASME/ANSI B1.5 and ASTM B1.8, define the dimensions, tolerances, and classes for Acme threads, guiding their manufacturing and application.
ASME/ANSI B1.5 Standard
The ASME/ANSI B1.5 standard is a critical document that specifies the dimensions and tolerances for general purpose Acme threads. This standard outlines the requirements for external and internal threads, including major, minor, and pitch diameters. It also defines the thread classes, such as 2G, 3G, and 4G, which dictate the degree of fit and clearance. The standard is essential for ensuring that Acme threads are manufactured and used consistently across different applications and industries, promoting interchangeability.
ASTM B1.8 Standard
The ASTM B1.8 standard is another key specification for Acme threads, particularly focusing on Stub Acme threads. This standard details the dimensions and tolerances for this specific type of thread, which is often used in applications with space constraints. It provides guidelines for both general and centralizing Acme threads, utilizing similar major and minor diameter allowances as the G and C series. Unlike ASME/ANSI B1.5, ASTM B1.8 is especially useful for applications that require a shorter thread height. It only includes one precision class, which corresponds to the 2G fit class.

Acme Thread Dimensions
Acme thread dimensions are critical for proper fit and function. These include major diameter, minor diameter, and pitch diameter. Standard charts provide these measurements based on the thread’s size and class, essential for both design and manufacturing.
Basic Dimensions Explained
The basic dimensions of an Acme thread are fundamental to its design and manufacturing. These nominal dimensions, such as the major, minor, and pitch diameters, form the basis for creating the threads. They are defined without allowances or tolerances, serving as a starting point. The specific series and class of the Acme thread, per standards like ASTM B1.5, dictate the allowable ranges for each dimension which are needed for machining and practical applications. These dimensions are crucial for ensuring proper fit and functionality in any assembly.
External Acme Thread Dimensions Chart
An external Acme thread dimensions chart provides essential measurements for male threads, adhering to standards like ASME/ANSI B1.5. This chart includes critical data such as the major diameter, which represents the crest of the thread, and the minor diameter, which is the root. The pitch diameter, thread per inch, and dimensional tolerances for various classes like 2G, 3G, and 4G are also detailed. This chart facilitates the selection and manufacturing of external Acme threads with the correct parameters. It is essential for ensuring proper fit and function.
Internal Acme Thread Dimensions Chart
The internal Acme thread dimensions chart specifies the measurements for female threads, following the ASME/ANSI B1.5 standard. This chart details the minor diameter, representing the crest of the internal thread, and the major diameter, which is the root. It also includes the pitch diameter, threads per inch, and dimensional tolerances for different classes, such as 2G, 3G, and 4G. This information is crucial for correctly machining or selecting internal Acme threads to ensure proper mating with external threads. It aids in precise design and manufacturing processes.

Acme Thread Classes
Acme threads are classified into 2G, 3G, and 4G, each providing varying degrees of clearance. These classes determine the fit between internal and external threads, impacting assembly and movement. 2G offers the most clearance, while 4G has the least.
Understanding 2G, 3G, and 4G Classes
The 2G, 3G, and 4G classes for Acme threads designate the level of fit and tolerance between mating threads. Class 2G provides the loosest fit, allowing for more clearance, suitable for general-purpose applications. Class 3G offers a tighter fit with less clearance, often used when greater precision is required. Finally, Class 4G provides the tightest fit and the least clearance, suited for high-accuracy applications. These classes affect the interchangeability and manufacturability of Acme threaded components, impacting their overall performance and functionality.
Applications of Acme Threads
Acme threads are widely used in machinery for converting rotary motion into linear motion. They are commonly found in vises, lead screws, and other applications needing high accuracy and the ability to handle large loads.
Common Uses in Machinery
Acme threads are integral components in various types of machinery, providing dependable linear motion. They’re frequently employed in vises, where they offer the necessary clamping force. Additionally, lead screws in machine tools, such as lathes and milling machines, rely on acme threads for precise and controlled movement of workpieces or cutting tools. The robust nature of acme threads also makes them suitable for heavy-duty applications in lifting jacks and other similar mechanisms, where the reliable transfer of power is essential.
Cutting and Manufacturing Acme Threads
The Landis system offers a reliable method for cutting Acme threads, providing greater operational latitude. Manufacturing these threads involves processes that ensure precise dimensions and the desired thread profile, meeting specific application requirements.
Landis System for Acme Thread Cutting
The Landis system stands out as a superior method for cutting Acme threads, offering enhanced control and precision. This system provides greater flexibility in tool operation compared to other techniques. Landis Solutions has expanded its capabilities to include those of Acme Fette, Geometric, Hamp;G, and Vers-O-Tool, offering comprehensive threading solutions. This approach ensures accurate thread profiles, which are essential for the proper functionality of Acme threads in various applications. The Landis method is recognized for its effectiveness and reliability in producing high-quality Acme threads.
Acme Thread Terminology
Understanding Acme thread terminology is crucial for proper design and manufacturing. Key terms include major diameter, minor diameter, pitch diameter, thread angle, and threads per inch (TPI). These terms define the physical characteristics of the thread.
Key Terms and Definitions
When discussing Acme threads, several terms are fundamental. The major diameter is the largest diameter of the thread, while the minor diameter is the smallest. The pitch diameter is the diameter at which the thread width and groove width are equal. Threads per inch (TPI) indicates the number of threads within one inch. Understanding these terms is essential for accurately using Acme thread charts and specifications. Additionally, thread angle refers to the 29-degree angle of the Acme thread profile.

Acme Thread Calculators and Charts
Acme thread calculators and charts are essential tools for accurately determining thread dimensions. These tools provide data for major, minor, and pitch diameters, along with other critical measurements, aiding in design and manufacturing processes.
Tools for Dimension Calculations
Calculating the dimensions of Acme threads is simplified through various tools, including online calculators and detailed charts. These resources allow users to determine critical measurements such as major, minor, and pitch diameters, thread height, and other essential parameters. These tools often incorporate standard specifications, such as those found in ASME/ANSI B1.5, ensuring accuracy and consistency. Using these tools helps in selecting the correct thread size and class for specific applications, which is crucial for proper functionality and interchangeability.
Where to Find Acme Thread Information
Information on Acme threads can be found in standards like ASME/ANSI B1.5 and ASTM B1.8. Additionally, many suppliers and manufacturers provide charts, technical data, and resources online.
Resources and Suppliers
For detailed Acme thread information, consult resources like the American National Standard ASME/ANSI B1.5 and ASTM B1.8. Many companies such as Landis Solutions, Rolled Threads Unlimited, and Roton Products, Inc. offer Acme threaded products and related tooling. Additionally, online databases from sources such as amesweb.info provide technical charts and tables. These resources are invaluable for designers, engineers, and machinists needing precise specifications for Acme thread components and tooling.