Technical Specifications

“All AMPG Shoulder Screws are Precision Made”
AMPG has assembled the most complete line of nonferrous shoulder screws manufactured in North America. Each shoulder bolt is made in one operation on state of the art Swiss Lathes. AMPG begins with precision ground DFARS compliant material. A finished part is made in one operation without the need for secondary broaching, slotting or thread rolling which can lead to many inconsistencies. AMPG’s process ensures shoulder diameter concentricity and tight tolerances. Each part is then carefully cleaned and packaged.


What Type of Shoulders Screws Are There?

AMPG manufactures two types of precision shoulder screws, Knurled Head and Smooth Head. Both types have shoulders that are held to a precise diameter. This dimension determines the type of component the shoulder can accommodate.

Knurled Head Shoulder Screw

Shoulder Screw diagram

Smooth Head Should Screw

Shoulder Screw Diagram

Knurled head shoulder screws are made to ASME shoulder tolerance and have been the industry standard suitable for use in machinery, and other critical mechanical applications. Knurled Head Shoulder Screws heads are knurled, stamped, or both to provide finger grip.

Smooth head, also known as precision-grade shoulder screws, have tighter shoulder tolerances making them ideal for use with ball bearings and other precision components.

How Do I Order Shoulder Screws?

Shoulder screws are specified by shoulder diameter and shoulder length. For instance, a 5/16 x 3/8-inch shoulder screw has a shoulder diameter of 5/16-inch and shoulder length of 3/8 inch. This differs from other screws and bolts, where this size represents the screws thread size and a thread length.

Some guidelines for choosing between the materials we produce are shown below.

AMPG Material Type chart

AMPG 303, AMPG 316, AMPG 316H5, AMPG 174, AMPG 405, AMPG Ti2, AMPG 661, AMPG 360 are ® Registered Trademarks of AMPG (Accurate Manufactured Products Group) and may not be used or reproduced without our permission.

What Type of Alloy Choices Are There?

Collection of alloy materials

Stainless Steel 18-8 (303)

  • Offers excellent corrosion resistance.

  • Resists chemicals, most dyes, food and nitric acid.

  • Corrosion-resistant material used for screws, bushings, nuts, and hardware.

  • May be mildly magnetic.

Stainless Steel 316 (316/316L)

  • Offers greater corrosion resistance than Type 303 stainless steel.

  • Resists salt water, acids, chlorides, alkalis and other industrial solvents.

  • Low-maintenance material used in commercial kitchens and food processing.

  • May be mildly magnetic.
    *AMPG uses dual certified Type 316/316L stainless material. Meets all 316 stainless properties but has lower carbon content, making it more suitable for welding.

Stainless Steel 416

  • Type 416 stainless can be hardened up to Maximum Rockwell C40 after heat treatment.

  • Resists acids, alkalis, fresh water and dry air.

  • As hardened, non-galling material used for fittings, gears, shafts and screws.

  • Magnetic.

Stainless Steel A286

  • Maintains superior corrosion resistance and strength at high temperatures, exceeding 17-4 PH performance.

  • Resists salt water, acids, chlorides, alkalis and other industrial solvents.

  • Used for fittings, valves, bolts and shafts.

  • Used in high heat/stress applications such as jet engines, gas turbines, and super-chargers.

  • Nonmagnetic.

Alloy Steel 4140/41L40

  • Thru-hardened to C24-32 per ASTM A108.

  • Used in high strength fasteners and components.

  • Common to Grade 8 designations in bolts and studs.

  • Requires a finish to resist rust, such as black-oxide treatment or zinc plating, but must be treated for hydrogen embrittlement.

  • Used for socket screws, studs and components.

  • Magnetic.

Mild Steel – Grade 2

  • Applies to an array of material designations, including AISI C1010; C1018: C1038 cold heading quality, or 12L14 for turned parts with cut threads.

  • Used in many general-purpose applications.

  • Requires a finish to resist rust, such as black-oxide or zinc plating.

  • Low-strength material used for bushings, washers, inserts, fittings, screws and nuts.

  • Used to manufacture our hex head product, which are often termed as “lawn mower bolts” due to their use as wheel axles.

  • Magnetic.


  • Softer material approximately two-thirds copper and one-third zinc.

  • Provides good resistance to rust and atmospheric corrosion.

  • Friction-resistant material used for gears, bearings, fasteners, and valves.

  • Sometimes used in anti-spark applications around flammable substances.

  • Yellow color desired in ornamental and decorative applications.

  • Nonmagnetic.

Stainless Steel 17-4 PH

  • Maintains excellent corrosion resistance and strength at high temperatures.

  • Used in automotive drive trains and heat exchangers.

  • Resists chemicals, most dyes, food and nitric acid.

  • High-strength material used for fittings, valves, bolts, and shafts.

  • Mildly magnetic.

Stainless Steel High Five® (316H5)

  • Higher strength grade of AISI 316 marine grade stainless steel.

  • Resists salt water, acids, chlorides, alkalis and other industrial solvents.

  • Corrosion-resistance material with strength equivalent to Grade 5 steel materials.

  • May be mildly magnetic.

  • Registered trademark and patented material of Accurate Manufactured Parts Group of Indianapolis, Indiana, USA.


  • Has the strength of mild steel with one third the weight.

  • Resists corrosion in wet environments.

  • Lightweight material used for fittings, hardware and fasteners.

  • Nonmagnetic.

Nickel Alloy 406 (Monel)

  • Also known as “nickel-copper alloy.”

  • Higher-strength corrosion and heat resistant material.

  • Excellent resistance in corrosive environments: sea water, some acids, alkalis.

  • Marine industry material used for propellers, heat exchangers, and valves.

  • May be mildly magnetic.

Titanium Grade 2

  • Very strong, lightweight, and corrosion resistant.

  • Resists chlorides, hypochlorites, chlorates, perchlorates and chlorine dioxide.

  • Used for chemical-processing equipment, heat exchangers and fasteners.

  • Nonmagnetic.

Titanium Grade 5

  • Also referred to as Titanium Gr5 (6AL-4V)

  • Two times stronger than Grade 2, and four times stronger than 316 stainless steel at nearly half the weight.

  • Resists chlorides, hypochlorites, chlorates, perchlorates and chlorine dioxide.

  • Lightweight material used for higher-strength fasteners, racing components and marine hardware.

  • Nonmagnetic.