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Inch, Metric & Mil-Spec MS51575 & MS51576 Precision Shoulder Screws

What are Precision Shoulder Screws?

Precision shoulder screws are specialized fasteners designed for applications where accuracy, precise alignment, and reliable connections are critical. They feature a cylindrical unthreaded shoulder that serves as a dowel or pivot point for rotating parts, and that are also used to hold parts together within a precision assembly. These screws, which are sometimes also called “high tolerance” shoulder screws, have tighter tolerances compared to standard or commercial shoulder screws (also known as shoulder bolts or stripper bolts). The thread class for these precision screws is 2A, and the tolerance on the shoulder diameter varies from +.000/-.001 to -.0005 to -.0015 depending upon the manufacturer.

Precision Shoulder Screws are generally classified as part of the electronic hardware family. Commonly used in high-tolerance industries such as aerospace, automotive, and electronics, these high-tolerance screws are ideal for rotation or sliding applications, serving as precision spacers with a bearing surface that supports a wide variety of uses and applications.

Precision Shoulder Screws at MF Supply

At MF Supply, we offer a complete range of precision shoulder screws, including both commercial and precision options to meet your specific needs. Choose from the Inch, Metric or Mil-Spec (MS51575 & MS51576) precision shoulder screws product categories below to see available sizes, materials and specifications. Standard materials offered include 18-8 / 300 and 416 Series stainless steel.

MF Supply is a leading supplier with expertise in precision shoulder screws. We stock and source an extensive inventory, including major brands and equivalents to BERG, Concord, Globe, PIC, Lyn-Tron and RAF—in inch/imperial, mil-spec and metric sizes, specifications, and materials.

Our catalog includes commercial and precision shoulder screws. Mil-spec parts/numbers, which include MS51575 & MS51576, are DFARS compliant and have full paperwork. Below, we highlight the primary styles of precision shoulder screws available.

Precision Shoulder Screws Styles Available - Slotted & Hex

Shoulder screws can belong to either the commercial or precision categories.

Commercial shoulder screws, also known as shoulder bolts or stripper bolts, adhere to the inch/imperial standard ANSI ASME B18.8.2, with shoulder diameters ranging from ¼" to 2". These screws feature a 3A thread class, with a shoulder tolerance of +.005 / -.005. (ASME B18.3?)

Precision shoulder screws, often called "tight tolerance" shoulder screws, aren't governed by any official ANSI or ASME standard. They come in shoulder diameters from 3/32" to ½", with a 2A thread class. The shoulder diameter tolerance varies by manufacturer, ranging from +.000/-.001 to -.0005/-.0015.

Precision shoulder screws have sockets, headless or thumb heads, and are usually accompanied with either hex or slotted drives.

Mil-Spec Slotted Precision Shoulder Screws (MS51575):

These slotted shoulder screws, made from 300 Series stainless steel, are designed to meet Mil-Spec MS51575 standards, making them perfect for military, aerospace, and industrial manufacturing applications where secure fastening and easy disassembly are required. They are available in shoulder diameters from 1/8" to 1/2" and in various lengths.

Mil-Spec Hex Socket Precision Shoulder Screws (MS51576):

Crafted from 300 Series stainless steel, these screws meet the stringent Mil-Spec MS51576 standards, delivering reliable performance and exceptional corrosion resistance in demanding military, aerospace, and defense applications. They are available in shoulder diameters from 4-40" to 3/8-16" and also in various lengths to meet your needs.

Inch Hex Socket Precision Shoulder Screws:

Our inch-sized precision hex socket shoulder screws, made from 300 & 416 Series stainless steel, are ideal for precision engineering projects requiring high-strength fasteners with exacting tolerances. Compliant with ANSI/ASME B18.3 standards, they are suitable for general & commercial engineering, automotive, and robotics applications, and are available in shoulder diameters from 1/8" to 1/2" with various lengths.

Inch Slotted Precision Shoulder Screws:

These slotted shoulder screws, also made from 300 & 416 Series stainless steel, are designed for easy installation and are perfect for applications requiring frequent adjustments. Compliant with ANSI/ASME B18.3 standards, they are ideal for use in electronics, instrumentation, and medical devices. Their sizes range from 1/8" to 1/2" shoulder diameter and are available in various lengths.

Metric Hex Socket Precision Shoulder Screws:

Our metric-sized hex socket shoulder screws, made from 18-8 / 300 & 416 Series stainless steel, are engineered for global compatibility, adhering to DIN 610 and ISO 7379 standards. They are ideal for machinery, industrial automation, and precision manufacturing applications, with shoulder diameters ranging from M3 to M12 and various lengths available.

Metric Slotted Precision Shoulder Screws:

These metric slotted shoulder screws, also made from 18-8 / 300 and 416 Series stainless steel, offer a secure fit with the flexibility for easy adjustments, making them perfect for precision assembly tasks. Compliant with DIN 610 and ISO 7379 standards, they are ideal for industrial equipment, optical devices, and measuring instruments, available in shoulder diameters from M3 to M12 and in various lengths.

Precision shoulder Screws Materials Available

Precision shoulder screws are available in 18-8 / 300 & 416 Series stainless steel, carbon Steel, brass and alloy steel. Each offer specific advantages that are tailored for demanding and precision engineering applications:

  1. 18-8 / 300 Series Stainless Steel: Precision shoulder screws made from 300 series stainless steel, specifically 18-8 stainless steel, contain 18% chromium and 8% nickel. These screws offer excellent corrosion resistance and maintain their mechanical properties across a wide temperature range (-320°F to 800°F). This material provides a good balance of strength and ductility, making these precision screws ideal for general-purpose applications in mildly corrosive environments.
  2. 416 Series Stainless Steel: Precision shoulder screws manufactured from 416 stainless steel are known for their high tensile strength, reaching up to 125,000 psi. This martensitic alloy offers excellent machinability due to the addition of sulfur and provides good corrosion resistance in mildly corrosive environments. These screws are magnetic and have high wear resistance, especially after heat treatment, making them suitable for applications requiring both durability and precision.
  3. Carbon Steel: Carbon steel precision shoulder screws are valued for their high tensile strength and affordability. With tensile strengths ranging from 60,000 to 100,000 psi, these screws offer excellent mechanical performance in high-stress applications. They are heat-treatable for enhanced hardness and are magnetic, making them ideal for structural and heavy-duty uses where durability is essential.
  4. Brass: Precision shoulder screws made of brass provide excellent corrosion resistance, particularly in marine environments, and offer good electrical conductivity, making them suitable for electronic components. Brass is also non-magnetic and aesthetically appealing, making it a preferred choice for decorative applications.
  5. Alloy Steel: Precision shoulder screws made from alloy steel are enhanced with elements like chromium and molybdenum, which provide superior tensile strength, impact resistance, and wear resistance. With tensile strengths that can exceed 200,000 psi after heat treatment, these screws are designed for high-stress, high-performance environments, such as those found in automotive and industrial machinery applications.

These material options ensure that precision shoulder screws can meet the specific demands of various industries, from aerospace and automotive to electronics and medical devices.

What are the Features & Benefits of Precision Shoulder Screws?

Precision shoulder screws offer a range of features and benefits that make them ideal for demanding applications. Below we list five features and benefits of precision shoulder screws:

  1. Tight Tolerance and Precision Manufacturing: Precision shoulder screws are manufactured with extremely tight tolerances, often within ±0.001 inches (±0.0254 mm) on critical dimensions such as shoulder diameter, length, and thread engagement. This high level of precision ensures consistent and repeatable performance in applications requiring exact component alignment, such as in robotics, precision machinery, and instrumentation.
  2. High Tensile Strength: Precision shoulder screws are typically made from high-strength materials, such as 18-8 / 300 and 416 series stainless steel, which have tensile strengths ranging from 70,000 to 125,000 psi (pounds per square inch). The high tensile strength allows these screws to withstand significant loads without deforming, making them ideal for structural applications in aerospace and automotive industries where reliability is critical.
  3. Corrosion Resistance: Constructed from corrosion-resistant stainless steel grades like 300 series (18-8 stainless) or 416 series, these screws offer excellent resistance to oxidation and chemical exposure. Corrosion resistance ensures long-lasting performance even in harsh environments, such as marine, chemical processing, or outdoor applications, reducing maintenance costs and downtime.
  4. Optimized for Load Distribution: The unthreaded shoulder of the screw is specifically designed to serve as a bearing surface, optimizing load distribution across the shoulder and preventing localized stress. This design feature minimizes the risk of galling or wear, especially in dynamic applications where components rotate or slide over the shoulder, such as in gear assemblies or pivot points.
  5. Versatility Across Standards and Applications: Precision shoulder screws are available in a wide range of standards, including Mil-Spec (MS51575 & MS51576), ANSI/ASME, and ISO, and in various sizes, from 1/8" to 1" in shoulder diameter for inch sizes, and M3 to M20 for metric sizes. This versatility ensures compatibility with a broad range of industrial applications, from military and aerospace projects to precision medical devices, allowing engineers to specify the exact screw required for their specific application.

What Is The Difference Betwen Inch & Metric Precision Shoulder Screws? (Coming Soon)

Precision Shoulder Screws Installation Steps

Installing a precision shoulder screw demands careful attention for accurate alignment and secure fastening. Follow these six steps to properly install a precision shoulder screw:

  1. Prepare the Components: Ensure both the shoulder screw and mating parts are clean and free of contaminants. Verify proper alignment and confirm that holes are correctly sized for the screw's shoulder and threaded portion.
  2. Select the Appropriate Tools: Choose the correct tool for the screw type (hex socket or slotted). If specific torque is required, use a calibrated torque wrench to prevent over-tightening or under-tightening.
  3. Insert the Screw: Carefully align and insert the screw's shoulder into the pre-drilled hole, ensuring a snug fit without excessive play. Turn the screw clockwise using the appropriate tool, making sure the threads engage smoothly without cross-threading.
  4. Tighten the Screw: Continue tightening until the shoulder is flush with or slightly below the component surface. Use a torque wrench to achieve the manufacturer's recommended torque value or tighten until snug for general applications without over-tightening.
  5. Verify Installation: Confirm that the shoulder is properly seated, and the components are correctly aligned, with the threaded portion fully engaged and no visible gaps between parts.
  6. Final Inspection: Gently test the assembly to ensure all components are securely fastened without unwanted movement or looseness. If issues are detected, loosen the screw, realign the components, and repeat the installation process.


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Why Buy Precision Shoulder Screws from MF Supply?

With over 50 years of experience as a supply chain partner to manufacturers, and deep and broad expertise in fasteners and electronic hardware, MF Supply can help with all your fastening and hardware needs.

We work with the best-established factories in the United States and abroad, and we also supply the most popular precision shoulder screws, including RAF, Pic, Berg, Lyn-Tron and less expensive generic alternatives to Grainger, McMaster and MSC. Our large inventory includes precision shoulder screws in 18-8 / 300 and 416 Series stainless steel, and in inch/imperial, mil-spec and metric sizes. Our mil-spec products, MS51575 & MS51576, are certified, DFARS compliant, and their full paperwork is available upon request.

Can't find what you're looking for? Email us at [email protected] for a custom quote. "We have the right screw for you" is our motto after all!