HOLO-KROME 32270 3/4-10 X 2-1/2" 杯端內六角止付螺絲 | 合金鋼熱處理黑色氧化（10入/包）

These set screws bit into the shaft cleanly with no slipping—the cup point really digs in. The thermal black oxide finish also seems like it'll resist rust better than the plain steel ones I've used before. Exactly what I needed for a stubborn pulley.

The hex socket drive seated perfectly on my Allen key, and the cup point bit into the shaft exactly where I needed it. Tapped them into a 3/4-10 hole and they haven't budged under vibration.

For the money, these set screws hold incredibly well — I used them to secure a heavy sprocket on a shaft and there’s zero slippage. The hex socket drive makes tightening a breeze, even in tight spots.