Shouldering The Burden: How Shoulder Screws Bear Weight

Posted on: 15 January 2019

Shoulder screws are unique fasteners in that they wear a "collar" around and just underneath the heat of the screw. The threaded part of the screw is typically what fastens things together, but it is the shoulder component that fascinates anyone who builds. In fact, these screws can turn and pivot, even while bearing (or shouldering) weight other fasteners could not. Just to give you an idea of the weight these clever fasteners can manage, here is a "page" from various engineering projects.

​Shoulder Screws Withstand Atmospheric Pressure

​Shoulder screws are used to construct and secure panels on spaceships and rockets. Where rigid rivets are not ideal, the shoulder screws will definitely do. Since anything that tries to leave Earth's orbit has to travel at several hundred miles per hour with intense force pressing inward on all sides, you can imagine the kind of gravitational weight and force every single screw inside and outside of the ship takes. 

​Shoulder Screws Help Move Loads Easily

Automated assembly lines use overhead cranes. Overhead cranes can move partial tons to full tons of materials or single-piece products. Built into those overhead cranes are shoulder bolts, which help parts of the crane rotate, spin, and pivot, all while feeling the pull of the weight that the cranes have to bear all day while the cranes are in operation. When the shoulder screws wear down, they are replaced to ensure that the cranes can continue doing the jobs they are meant to do.

​Shoulder Screws/Bolts Aid in Pouring Molten Liquids

One such example is an overhead crucible of molten metal on freely swinging handles and an arm that keeps the crucible from tipping and pouring accidentally. When it comes time to pour, the shoulder bolts allow for the crucible to tip and pour. Since these screws/bolts come in all sizes, you can easily spot them when they are in use in this fashion and recognize the important and heavy job they have to do. 

Heavy, Spinning Machinery

​Some milling machines that spin rapidly may incorporate shoulder screws/bolts of substantial size into the construction of the machines. The machines rely on the free-moving shoulder girdles of these fasteners that allows the milling machines' inner mechanisms to spin with minimal lubrication and minimal wear and tear. Meanwhile the size of these milling machines is massive, and the weight matches the size, pound for pound, ton for ton.