Cap screws

Cap screws: A fastener for machine parts, threaded along the whole length of its shank and held by threads tapped in the hole in which it is screwed.

A socket cap screw, also known as a socket head capscrew, socket screw, or Allen bolt, is a type of cap screw with a cylindrical head and hexagonal drive hole. The term socket head capscrew typically refers to a type of threaded fastener whose head diameter is nominally 1.5 times that of the screw shank (major) diameter, with a head height equal to the shank diameter. Forged heat-treated alloy examples are high strength fasteners intended for the most demanding mechanical applications, with special alloy formulations available that are capable of maintaining strength at temperatures in excess of 1000 degrees F (587 degrees C).

The term cap screw refers to many different things at different times and places. Currently, it most narrowly refers to a style of head.

black oxide hex drive socket cap screw black socket head cap stainless machine screws hex socket cap m3 machine screw
M3 stainless steel machine screws hex socket cap M4 cylindrical head stainless steel socket head cap screws M4 stainless steel machine screws
Self sealing screw socket cap DIN 912 yellow patch . socket head cap captive half threaded screw Tamper-proof screws self sealing screws socket cap machine screws

In addition to the socket head capscrew design, other head designs include low head, button head and flat head, the latter designed to be seated into countersunk holes. A hex key (sometimes referred to as an Allen wrench or Allen key) or hex driver is required to tighten or loosen a socket screw. Socket head capscrews are commonly used in assemblies that do not provide sufficient clearance for a conventional wrench or socket.

More broadly, and more commonly, it refers to the group of screws: shoulder screws, hex heads, counter-sunk heads, button heads, and fillister heads.

18-8 stainless steel washer head torx drive screws supplier 6mm allen socket stainless steel flat head screws supplier black truss head machine screws manufacturers
black zinc finish torx drive machine screws manufacturers brass socket head brass countersunk screws wholesale cheese head slotted brass screws for sale
custom flat head socket stainless steel screws wholesale Custom hexagonal socket head cap screw wholesale custome truss head hex socket machine screws supplier
double sems truss socket cap head screw manufacturer double washer hex socket cap sems screws manufacturer nylon patch torx drive washer head machine screws

Hex cap screw and hex bolt

A hex cap screw is a cap screw with a hexagonal head, designed to be driven by a wrench (spanner). An ASME B18.2.1 compliant cap screw has somewhat tighter tolerances than a hex bolt for the head height and the shank length. The nature of the tolerance difference allows an ASME B18.2.1 hex cap screw to always fit where a hex bolt is installed but a hex bolt could be slightly too large to be used where a hex cap screw is designed in.

Combination indented hex phillips screw with big washer external tooth washer hex head machine screw manufacturer indented hex washer head phillips drive sems screw with wave washer
indented hex washer head slotted drive thread cutting screws phillips drive sems indented hex washer head screws manufacturer stainless steel sems phillips pan hex washer head screw
Zinc-Nickel Plating hex washer head thread forming screw White and black flange self-tapping screws supply 6-32 x 58 square conical washer phillips hex head sems fasteners screw

In the United States, cap screws are defined by ASME B18.6.2 and ASME B18.3. In the past, the term cap screw, in general, referred to screws that were supposed to be used in applications where a nut was not used, however the characteristics that differentiated it from a bolt vary over time.

In 1910, Anthony defined it as screw with a hex head that was thicker than a bolt head, but the distance across the flats was less than a bolt’s.

In 1913, Woolley and Meredith defined them like Anthony, but gave the following dimensions: hex head cap screws up to and including 7⁄16 inch (11.1125 mm) have a head that is 3⁄16 inch (4.7625 mm) larger than the shank diameter; screws greater than 1⁄2 inch (12.7 mm) in diameter have a head that is 1⁄4 inch (6.35 mm) larger than the shank. Square head cap screws up to and including 3⁄4 inch (19.05 mm) have a head 1⁄8 inch (3.175 mm) larger than the shank; screws larger than 3⁄4 inch (19.05 mm) have a head 1⁄4 inch (6.35 mm) larger than the shank. In 1919, Dyke defined them as screws that are threaded all the way to the head.

You may also like All types of screws

If you’re interested in purchasing screws, be sure to check out the wide range of standard and custom products from Yuhuang Electronics Technology Co., Ltd.

For more information about cap screws from us at www.yhscrew.com, please email us at info@www.yhscrew.com. We look forward to hearing from you.