limitscrew

Limitscrew is a term used in mechanical design to describe an adjustable screw that sets the end of travel for a moving part. The limitscrew functions as a physical stop, defining a maximum or minimum position by contacting a surface or engaging a dedicated stop point within a component or housing. It is often used where precise but simple travel limitation is required, and it may be paired with a lock mechanism to resist undesired movement.

Construction and operation typically involve a threaded screw, often a set screw or small machine screw, with a contact end that can be pointed, flat, or slightly rounded to suit the application. The screw is installed in a fixed body and adjusted by turning in or out to bring the moving part to the desired stop position. A locking feature such as a locknut, thread-lock adhesive, or a second threaded component is commonly used to prevent drift due to vibration or thermal effects. Materials commonly include steel or stainless steel, with coatings chosen for wear resistance or corrosion protection.

Applications are widespread across mechanical systems that require repeatable limits, including CNC machines, linear guides, automation actuators, robotics joints, and door or valve assemblies. In practice, limitscrews provide a low-cost, robust method for establishing end-of-travel without sensors, though they may wear over time and require periodic inspection and adjustment.

Maintenance and adjustment involve checking alignment of the stop surface, confirming the end-of-travel position, and ensuring the screw remains securely locked. Replacing worn screws and inspecting for burrs or thread damage helps maintain reliable performance.

See also: end stop, travel stop, limit switch.