These are Acorn Nut Screws. They are also referred to as Luke Rivets for knife handles. Acorn Nut Screws are 3-piece threaded fasteners that work
Industrial Acorn Nuts & Cap Nuts for sale
Acorn Nut Fasteners - Luke Rivets for Handles - (.250 HD x 8-32 US x 1 L) - Stainless Steel - (10 Pk)
KYDEX™ Sheet - Coyote Brown - (.080) - (1ft x 1ft)
Acorn Nut Fasteners - Luke Rivets for Handles - (.312HD x 8-32US x 1L) - Brass - (10 Pk)
Combat Survivor Knife Kit - DIY Knife Kit - (Blade Blank & Pinstock Only)
Acorn Hex Cap Nuts
Hillman #8 x 32 Brass Wood Insert Nut (2-Count) in the Lock Nuts department at
HOLSTEX™ - DIY Thermoform Sheet - Carbon Fiber/Tactical - (Olive Drab) - (.080) - (1ft x 1ft)
Combat Survivor Knife Kit - DIY Knife Kit - (Blade Blank