Precision adjustment screws are precision hardware components that have a very fine thread count. Thread density is usually up to 508 threads per inch (TPI). Thread class for precision adjustment screws is typically 3A and 3B for its mating components because of the close tolerance requirements for these products.

Applications

Precision adjustment screws are used to provide micro positioning on precision instruments such as tables, optical mounts, microscopes, analytical instruments, and flow metering devices. They are used in applications in which fine linear adjustment or measurement is required. They are also commonly referred to as fine adjustment screws or micrometer screws and are often supplied w?th a corresponding threaded?bushings. 

Types

The threads of precision adjustment screws are classified as ether fine or ultra fine. Fine adjustment screws have between 40-100 TPI (0.5mm to 0.2mm pitch) and ultra fine adjustment screws have betw?en 100-508 TPI (0.2 mm to 0.05 mm pitch).

Specificati?ns

Precision adjustment screw are typically made from 18-8 (303) stainless steel with rolled or cut threads. The p?imary specifications for these products are dia?eter, TPI (threads per inch), lead, and sensitivity.

The lead is the linear range of travel per screw revolution. To calculate the lead divide 1 inch by the TPI. Some examples of TPI and corresponding lead values are:

• 20 TPI (.050" per rev.)
• 127 TPI (.0079" per rev.)
• 200 TPI (.005" per rev.)
• 254 TPI(.0039" per rev.)
• 508 TPI (.0019" per rev.)

Sensitivity is the linear distance traveled based on one degree rotation of the screw. It is measured in micrometers, commonly known as a microns (SI symbol: µm).

Precision adjustment screws are also available with a selection of drive knobs, drive connections, and position locking features.

References

Images credit:

Grainger Industrial Supply