Electro Hardware THS1004M01F21 Brass Thumb Screw 4-40

Product Description

The ELECTRO HARDWARE THS1004M01F21 is a brass thumb screw with a knurled head and shoulder, designed for hand-tightened fastening applications in mechanical assemblies, enclosures, and panel work. Threaded to 4-40 UNC, it delivers reliable engagement in fine-threaded applications without the need for tools. The knurled head provides a secure grip for repeated removal and reinstallation. At 0.75 inches overall length and a head diameter of 0.375 inches, this fastener suits tight-clearance installations where a standard slotted or hex fastener is not practical. It carries a zinc finish over a solid brass body.

This thumb screw is suited for light-duty industrial, electrical, and instrumentation panel assembly where hand-operated fastening is required. The integral shoulder provides positive seating and helps prevent over-insertion. Typical applications include equipment covers, access panels, junction boxes, and fixture mounting in settings where tools may not be available or frequent access is needed by technicians and assembly personnel.

Key Features

• 4-40 UNC thread for fine-threaded engagement in light-duty assemblies
• Knurled head allows tool-free hand tightening and removal
• With-shoulder design provides positive seating and controlled insertion depth
• Solid brass construction with zinc finish for corrosion resistance
• Compact head profile: 0.375 inches diameter, 0.1875 inches height
• Meets multiple material and finish standards including ASTM B633

Compatibility

Designed for use in applications requiring a 4-40 UNC threaded thumb screw with a knurled head and shoulder. Suitable for standard inch-measurement threaded inserts and tapped holes conforming to UNC 4-40 specifications.

Installation Notes

Installation requires no special tools — the knurled head is intended for hand tightening only. Verify the mating thread is clean and free of debris before installation to avoid cross-threading the fine 4-40 thread. Do not apply excessive torque, as over-tightening a hand-turn fastener can damage the threads or the mating material. Follow applicable assembly standards for the equipment type being serviced.