Gibraltar 31051G Steel Thumb Screw 1/2-13 Lobed Head

Product Description

The GIBRALTAR 31051G is a 12L14 steel thumb screw with a lobed aluminum head and a dog point tip, designed for manual fastening applications where tools are not required for routine adjustment or clamping. The fastener features a 1/2-13 UNC thread and an overall length of 4.5 inches. The lobed head provides a secure grip surface for hand-tightening, while the dog point tip aids in alignment during installation. A black oxide finish provides a basic level of corrosion resistance and a uniform dark appearance. This type of fastener is commonly installed by machinists, millwrights, and maintenance technicians working on fixtures, jigs, and mechanical assemblies.

This thumb screw is suited for use in industrial, manufacturing, and maintenance environments where frequent manual adjustments are required. The shoulder construction adds lateral stability in applications where the fastener must resist side loading. The 1/2-13 UNC thread size makes it compatible with standard inch-series tapped holes used widely across machine fixtures and tooling setups. Sold individually, this fastener fits applications requiring a single replacement or low-volume procurement.

Key Features

• 12L14 steel body with black oxide finish for corrosion resistance
• Lobed aluminum head — 2.5 inches diameter, 1.5 inches height — for hand-tightening without tools
• Dog point tip, 0.3438 inches (11/32 inches) diameter and 0.25 inches long, for alignment during engagement
• With-shoulder construction for lateral load resistance
• 1/2-13 UNC thread standard, 4.5 inches overall length
• Meets TCMAI standards

Compatibility

Designed as a standard inch-series replacement thumb screw for machine fixtures, jigs, and tooling assemblies using 1/2-13 UNC tapped holes.

Installation Notes

Installation is performed by hand or with minimal tooling into a pre-tapped 1/2-13 UNC hole. Verify the tapped hole depth and thread condition before installation to avoid cross-threading or bottoming out. Do not use power tools to drive this fastener, as the lobed head is intended for hand operation only. Ensure the mating assembly is de-energized or depressurized as required by the specific machine or fixture before adjusting or replacing this fastener.