Miniature thumb screws. Screws - Captive - Retractable - Steel Also see combined categories: ASTM F - alloy steel. All Captive Screws Knurled Head. All Thumb Screws Knurled head stainless steel thumb screws with an integral washer. All Thumb Screws. Widely used in power generation, chemical processing, aerospace and medical applications. Ratchet mechanism allows screw to be tightened down by hand, but a tool is needed to loosen. Grade 5 6Al-4V is a high strength titanium alloy. Request Samples Or A Quote. Collet Clamp Nm. Contact Us.