18-8 Stainless Steel Hex Head Cap Screws

18-8 stainless steel hex head cap screws are externally driven threaded fasteners designed for securing machinery, structural components, equipment, fixtures, and industrial assemblies. The six-sided hex head permits installation with standard sockets, box-end wrenches, or open-end wrenches, making these fasteners suitable for applications where an internal hex drive is unnecessary or external wrench access is preferred.

Manufactured from 18-8 stainless steel, these hex head cap screws provide general corrosion resistance for many industrial environments exposed to moisture, humidity, and routine washdown. They are commonly specified for machinery, processing equipment, pumps, motors, conveyors, material handling systems, OEM assemblies, maintenance repairs, agricultural equipment, construction equipment, and general industrial applications where corrosion resistance and dependable fastening performance are required.

Proper fastener selection should consider thread size, screw length, head dimensions, wrench size, thread engagement, mating materials, installation access, and the environmental conditions in which the assembly will operate. Individual product pages provide verified dimensional information to assist engineers and purchasing professionals in selecting the appropriate fastener.

Cold Headers supplies 18-8 stainless steel hex head cap screws in a broad range of inch thread sizes and lengths, including standard and difficult-to-source configurations. Our catalog is designed to help engineers, distributors, maintenance professionals, and purchasing teams quickly locate the exact fastener required for industrial applications.

Why Choose 18-8 Stainless Steel Hex Head Cap Screws?

  • External hex drive: Compatible with standard sockets and wrenching tools.
  • 18-8 stainless steel: Provides general corrosion resistance for many industrial environments.
  • Versatile fastening: Suitable for machinery, equipment, OEM manufacturing, and maintenance applications.
  • Broad size selection: Available in numerous thread sizes and lengths, including difficult-to-source configurations.
  • Verified engineering dimensions: Product pages include thread size, screw length, head dimensions, wrench size, and additional dimensional information where available.

Selecting the Correct Hex Head Cap Screw

Begin by confirming the required thread size and screw length. Review the wrench size, head dimensions, thread engagement, installation clearance, mating materials, and service environment before selecting a fastener. Final material selection should reflect the mechanical and environmental requirements of the assembly.

Cold Headers Inc. has supplied specialty industrial fasteners since 1962. Our catalog helps engineers, distributors, maintenance teams, and purchasing professionals locate exact sizes, uncommon lengths, and difficult-to-find hex head cap screws without unsupported inventory claims.

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.

Request Information Search by Specification
Unit of Measure
Items
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4-40 x 1/4 18-8 Stainless Steel Hex Head Cap Screw
List Price (per 100 pieces) $12.00
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4-40 x 5/16 18-8 Stainless Steel Hex Head Cap Screw
List Price (per 100 pieces) $12.25
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4-40 x 3/8 18-8 Stainless Steel Hex Head Cap Screw
List Price (per 100 pieces) $12.50
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4-40 x 7/16 18-8 Stainless Steel Hex Head Cap Screw
List Price (per 100 pieces) Call or Email for Pricing
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4-40 x 1/2 18-8 Stainless Steel Hex Head Cap Screw
List Price (per 100 pieces) $12.75
Description N/A

4-40 x 1/4 18-8 Stainless Steel Hex Head Cap Screw is an externally driven fastener for wrench or socket installation from the side of the head. In this size range it is treated as a hex head machine screw, with the hex head driven by external tooling rather than an internal socket.

Common application reviews include machine frames, guard panels, and bracket assemblies. External hex drive is useful when a wrench or socket can reach the head from the side and a counterbore would add unnecessary machining.

18-8 stainless steel is an 18% chromium and 8% nickel austenitic stainless material used for ordinary atmosphere, moisture exposure, washdown, and clean appearance. Cold Headers has supplied specialty fasteners since 1962 and supports exact-size sourcing for hard-to-find industrial hardware.

Technical Highlights

  • Material: 18-8 Stainless Steel
  • Thread Size: 4-40
  • Length: 1/4 in.
  • Head Style: Hex
  • Drive: External Hex (wrench or socket driven)
  • Width Across Flats: 0.428-0.438 in.
  • Wrench Size: 7/16 in.
  • Head Height: 0.150-0.163 in.

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.

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For drawings calling out 4-40 x 5/16, this 18-8 stainless hex head fastener supports assemblies where top-drive clearance is not required. In this size range it is treated as a hex head machine screw, with the hex head driven by external tooling rather than an internal socket.

Common application reviews include food processing skids, washdown equipment, and packaging lines. The head can be tightened with standard side-access tooling, which helps where top clearance is limited by covers or nearby components.

18-8 stainless steel is an 18% chromium and 8% nickel austenitic stainless material used for ordinary atmosphere, moisture exposure, washdown, and clean appearance. Cold Headers helps buyers match uncommon lengths, older drawings, and replacement sizes without changing the protected SKU data.

Technical Highlights

  • Material: 18-8 Stainless Steel
  • Thread Size: 4-40
  • Length: 5/16 in.
  • Head Style: Hex
  • Drive: External Hex (wrench or socket driven)
  • Width Across Flats: 0.489-0.500 in.
  • Wrench Size: 1/2 in.
  • Head Height: 0.195-0.211 in.

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.

 		N/A

4-40 x 3/8 18-8 Stainless Steel Hex Head Cap Screw is built for conventional hex-head fastening through clearance holes or into tapped parts. In this size range it is treated as a hex head machine screw, with the hex head driven by external tooling rather than an internal socket.

Common application reviews include pump bases, flanges, and plant-service hardware. Use it through a clearance hole with a nut or into a prepared tapped hole when the drawing calls for a stainless hex-head fastener.

18-8 stainless steel is an 18% chromium and 8% nickel austenitic stainless material used for ordinary atmosphere, moisture exposure, washdown, and clean appearance. For production, repair, and distributor sourcing, Cold Headers can help confirm the exact diameter and length before quoting.

Technical Highlights

  • Material: 18-8 Stainless Steel
  • Thread Size: 4-40
  • Length: 3/8 in.
  • Head Style: Hex
  • Drive: External Hex (wrench or socket driven)
  • Width Across Flats: 0.551-0.562 in.
  • Wrench Size: 9/16 in.
  • Head Height: 0.226-0.243 in.

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.

 		N/A

Use the 4-40 x 7/16 18-8 stainless hex head cap screw when the assembly calls for side wrench access and a general-purpose bolt pattern. In this size range it is treated as a hex head machine screw, with the hex head driven by external tooling rather than an internal socket.

Common application reviews include HVAC equipment, conveyor structures, and retrofit repairs. Stainless-on-stainless threads can gall when run down fast or dry; moderate installation speed and thread lubricant are prudent on larger diameters.

18-8 stainless steel is an 18% chromium and 8% nickel austenitic stainless material used for ordinary atmosphere, moisture exposure, washdown, and clean appearance. Cold Headers' catalog work is strongest where the requested size, material, and application details need a careful match.

Technical Highlights

  • Material: 18-8 Stainless Steel
  • Thread Size: 4-40
  • Length: 7/16 in.
  • Head Style: Hex
  • Drive: External Hex (wrench or socket driven)
  • Width Across Flats: 0.612-0.625 in.
  • Wrench Size: 5/8 in.
  • Head Height: 0.272-0.291 in.

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.

 		N/A

The 4-40 x 1/2 size in 18-8 stainless is suited to hex-head fastening where frames, brackets, or guards need serviceable external drive access. In this size range it is treated as a hex head machine screw, with the hex head driven by external tooling rather than an internal socket.

Common application reviews include outdoor hardware, equipment covers, and access panels. 18-8 stainless may pick up slight magnetism from cold working, which is normal for this austenitic stainless material.

18-8 stainless steel is an 18% chromium and 8% nickel austenitic stainless material used for ordinary atmosphere, moisture exposure, washdown, and clean appearance. When standard catalog searches are too broad, Cold Headers supports precise sourcing for stainless fasteners and related socket products.

Technical Highlights

  • Material: 18-8 Stainless Steel
  • Thread Size: 4-40
  • Length: 1/2 in.
  • Head Style: Hex
  • Drive: External Hex (wrench or socket driven)
  • Width Across Flats: 0.736-0.750 in.
  • Wrench Size: 3/4 in.
  • Head Height: 0.302-0.323 in.

Call 773-775-7900 or email Sales@coldheaders.com for pricing, availability, or a quote.
Brands N/A Cold Headers, Inc.
Diameter N/A 4-40
Length N/A 1/4 in N/A 5/16 in N/A 3/8 in N/A 7/16 in N/A 1/2 in
Maximum Width Across the Flats N/A 0.438 in N/A 0.500 in N/A 0.562 in N/A 0.625 in N/A 0.750 in
Minimum Width Across the Flats N/A 0.428 in N/A 0.489 in N/A 0.551 in N/A 0.612 in N/A 0.736 in
Maximum Width Across Corners N/A 0.505 in N/A 0.577 in N/A 0.650 in N/A 0.722 in N/A 0.866 in
Minimum Width Across Corners N/A 0.488 in N/A 0.557 in N/A 0.628 in N/A 0.698 in N/A 0.840 in
Maximum Head Height N/A 0.163 in N/A 0.211 in N/A 0.243 in N/A 0.291 in N/A 0.323 in
Minimum Head Height N/A 0.150 in N/A 0.195 in N/A 0.226 in N/A 0.272 in N/A 0.302 in
Material N/A 18-8 Stainless Steel
Quantity N/A 100
Package Type N/A Box
Note N/A Less Than Package Quantity Specified Plus 25%.