Mutual Screw & Supply

#4-40 X 3/8" Socket Cap Screws | Flat Head Hex Socket Drive | Nylon Pellet | Fully Threaded | Alloy Steel Thermal Black Oxide (100 / Pkg.)

#4-40 X 3/8" Socket Cap Screws | Flat Head Hex Socket Drive | Nylon Pellet | - Main image
$101.13 $142.44 In stock

These #4-40 x 3/8" socket cap screws are manufactured from Alloy Steel Thermal Black Oxide, featuring a hex socket drive. They are well suited to machinery, tooling, jigs, and precision assemblies.

  • Material and finish: Alloy Steel Thermal Black Oxide
  • Head style: Flat Head
  • Drive: Hex Socket Drive
  • Thread style: Fully Threaded
  • Thread size: #4-40
  • Length: 3/8"
  • Applications: Machinery, tooling, jigs, and precision assemblies

Specifications

  • Product type: Socket Cap Screws
  • Head style: Flat Head
  • Material: Alloy Steel
  • Finish: Thermal Black Oxide
  • Drive type: Hex Socket Drive
  • Thread style: Fully Threaded
  • Thread size: #4-40
  • Length: 3/8"
  • Threads per inch: 40
  • Measurement type: Inch
  • Pack quantity: 100 per package
Before you pay

Check the method and total at checkout.

When it ships

Allow for processing time as well as the journey to you.

Standard Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

Express Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

View policy
If you need a refund

Keep your order number and contact the store to start.

Please contact us for the refund processing timeframe before returning an item.

View policy
Delivery costs

Review the cost for your destination and chosen service.

Standard Shipping · United States: $0.00

Express Shipping · United States: $3.99

View policy
Returning an item

Check the return conditions before sending anything back.

United States · Return window (days after delivery): 30. Return method: By mail. Return postage: Seller pays.

View policy

Customer Reviews (4.2 / 5 · 5 reviews)

Michael ★★★★★

The nylon pellet in these #4-40 x 3/8" screws is a lifesaver for keeping them snug on my jig fixtures—no more worrying about them backing out mid-run. They’re fully threaded and the black oxide finish looks clean on the tooling, just what I needed for precision assemblies.

Evelyn S. ★★★★☆

The black oxide finish gives them a nice uniform look, and the nylon pellet does keep them from backing out during vibration. Took a star off because a couple screws in the bag had slightly burred threads, though they still seated fine in my jig.

Owen M. ★★★★☆

I was pleasantly surprised by how tight these nylon pellet screws hold under vibration—much better than standard machine screws. The black oxide finish seems durable enough for my jig setup. Only wish the package included a few extras.