Precision Shoulder Screws!? What the heck are those?

What the heck are Precision Shoulder Screws?

Here we go again, with our “what the heck is that” series refreshed for 2023, where we discuss some of the unique fasteners and electronic hardware that manufacturers use in the design and assembly of their products. Today, we will re-introduce you to the Shoulder Screw!

What is a Precision Shoulder Screw? 

Shoulder Screws, which are sometimes called Shoulder Bolts or Stripper Bolts, are (generally) hex socket screws with an enlarged, unthreaded cylindrical shoulder under the head.  They are comprised of 3 main parts: the head, the shoulder and the thread.  They come in two basic categories, “Commercial” and “Precision”.

Commercial Shoulder Screws are made to inch standard ANSI ASME B18.8.2.  The size range for the shoulder diameter is from ¼ to 2”.  The thread class is 3A and the tolerance on the shoulder is +.005 /  -.005.

Precision Shoulder screws are sometimes referred to as “tight tolerance” shoulder screws. They are not governed by any official ANSI or ASME standard. The size range for the shoulder diameter is from 3/32 to ½.  The thread class is 2A and the tolerance on the shoulder diameter varies from +.000/-.001 to  -.0005 to -.0015 depending upon the manufacturer. Now that’s precise!

Who uses Shoulder Screws?

Just as Dowel Pins and Retaining Rings are used to locate or hold parts together within a precision assembly or a fixture, so are Precision Shoulder Screws.

Yet shoulder screws are more versatile. When installed, the unthreaded shoulder acts as a shaft for rotating items such as bearings and bushings, precision spacing, machinery support, and motion guiding. Precision Shoulder screws exacting tolerances make them ideal for use with other precision components.

They are broadly used across various applications in many industries, including: aerospace, electrical motors, hydraulic equipment, instrumentation, tooling and fixtures, machinery, military and many more.

What do I need to consider when selecting Shoulder Screws?

Although Shoulder Screws are offered in a multitude of materials and styles, when it comes to the main commercial and precision offerings, there are a few main issues to consider.

Which Drive and Head Style?

Precision shoulder screws are readily available in hex socket and slotted drives.  Philips drives are available in certain sizes. Torx and Star are available for special order. Typical head styles are a modified fillister with a flat top where the head diameter is about twice the head height. Low head fillisters are available in certain sizes

Which material do I need?

Precision shoulder bolts are readily available in Type 18-8/303 Stainless Steel and 416 Stainless Steel.  316 Stainless Steel, Alloy and other exotic materials are available for special order.

Are there other factors to consider?

When ordering Precision Shoulder screws, specify the Shoulder Diameter, Shoulder length, thread size, material and drive type. For example, an example of a typical Precision Shoulder screw is a ¼ shoulder x ½ long x 10-32 thread in SS18-8 with a hex-socket drive. Non-locking is the most popular style, but locking may also be available.

Precision Shoulder Bolts  often show up under their brand name.  Some of the most popular brands include: BERG, Concord, Globe, PIC, Lyn-tron and RAF. A comprehensive selection of Shoulder Screws is also offered by McMaster-Carr (tight tolerance series), MSC and Grainger.

Finally, Precision Shoulder Screws can also show up under their Mil-spec numbers, which include MS51575 & MS51576 and are DFARS compliant with full paperwork.

Precision Shoulder Screws at MF Supply

We currently offer:

  • The full range of commercial and mil-spec parts, including parts that are DFARS and ROHS compliant.
  • MS51576 Now available for online purchase!
  • Brand names and generic equivalents.
  • Custom made parts per print in non-standard and exotic materials and finishes.
  • Inch, Metric and Mil-Spec sizes.

For more detailed information on Precision Shoulder Screws, visit us at our website or Request a Quote today, and our MF Supply team of sourcing experts can help you find what you need. “Finding the right screw for you” is our tag line after all!

Book a one-on-one consultation with our President, Robin, to discuss how MF Supply can help you solve your Industrial Sourcing, Fastener, and Safety concerns.

MF Supply Work With Us

Six Reasons To Buy From MF Supply

  • Full eCommerce Enabled Website With Technical Manual Available 24/7 – Visit our website and Create a New Account, track online orders, browse our product catalog, check technical specs, subscribe to our blog, or buy online.  We are adding items and improving functionality daily!
  • Same Day Shipping From The USA – Our hardware products are in stock and ship to you directly from our USA based distribution centers. 
  • Functional Equivalents To Expensive Brand Names- We stock and source alternatives to brand name fasteners, reducing long lead times and saving you money.
  • Creatively Solve Problems – We are sourcing experts, offer competitive pricing and specialize in finding hard to find parts and reducing long deliveries.
  • One-Stop Shopping On Certified Hardware – We stock and source a full line of fasteners including Mil-Spec, DFARS compliant and other industrial products.
  • WBE/WOSB Woman Owned Certified Small Business – To meet your diversity & set-aside needs.

MF Supply is a WBE/WOSB certified supply chain partner to business, industry and government.  We are sourcing experts and stocking distributors of Hardware, Precision & Mil-Spec Fasteners and Safety supplies.  For more than 50 years, we have been supplying manufacturers in the electronics, industrial, commercial, aerospace and military markets with the full range of fastener products and services.  Our Cage Code is 58QG4 and our registered name is RL Supply Inc dba MF Supply. 

New Inch & Mil-Spec Precision Shoulder Screws

MF Supply is happy to announce that in addition to our Metric Precision Shoulder Screw line, we are now offering Inch and Mil-Spec Precision Shoulder Screws, including MS51575 & MS51576. These new products are available for RFQ directly from!

As your source for functional equivalents to expensive brand name fasteners, we know how to save you money and reduce long lead times commonly found with brand name fasteners.

Here is an example of a functional equivalent in action:

The following screw, available for RFQ at, has a generic description as follows:
3/16” shoulder diameter x 1” long x 8-32 thread in SS18-8 (300 Series) with a hex-socket drive. Below we list seven OEM brands (yes, seven!) including their part numbers, and one Mil-Spec part number that are all functional equivalents:

    • Grainger 6JY20
    • Lyn-tron SS7431-00
    • McMaster-Carr 94035A208
    • MSC Industrial 67313726
    • Pic Design 4423
    • RAF 6931-SS
    • WM Berg PZ-14-3
    • MS51576-14

Visit our cross reference chart and plug in your part number to see if a functional equivalent is available. Popular precision shoulder screw brands include: Amatom, Cambion, Concord, Globe, HH Smith, Keystone, Lyn-tron, Misumi, Pic Design, RAF, Unicorp and WM Berg. A comprehensive selection of Precision Shoulder Screws is also offered by McMaster-Carr (tight tolerance series), MSC, and Grainger.

We encourage you to check out our Precision Shoulder Screw Buyer’s Guide on our blog where we share “Five things you need to know” to have the most efficient shopping and buying experience.

Send us your part number
to see if we can cross to a functional equivalent,
shorten lead times & save you money!

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Five Reasons to buy from MF Supply

  1. Huge inventory including 18-8, 303, 316, 416, A2, A4 stainless in Inch & Metric, including major brands and functional equivalents
  2. Domestic parts with full paperwork and Certificate of Conformanceavailable
  3. Custom Sizes, Materials and Plating options available
  4. Creatively solve problems including hard to find parts and long lead times
  5. WBE/WOSB Woman Owned Certified Small Business