5/8"-18 Hex Cap Screws

5/8-18 Hex Cap Screws in all available lengths, grades, materials, and finishes. This collection covers every 5/8-18 option in stock — use the filters to narrow by length, grade, material, and finish.

5/8-18 Thread Specifications

• Nominal diameter: 0.625"
• Threads per inch: 18
• Tap drill (75% thread): 37/64" (0.578")
• Clearance hole (close fit): 41/64" (0.641")
• Clearance hole (free fit): 21/32" (0.656")

To thread a 5/8-18 hole, drill with a 37/64" (0.578") tap drill for a standard 75% thread. For a clearance hole that the 5/8-18 screw passes through, use 41/64" (0.641") for a close fit or 21/32" (0.656") for a free fit. Pair with a matching 5/8-18 nut or tapped hole.

Orders before 12 PM ET ship same day.