Maintenance Technician 2026 Complete Practice Test

To determine the effective threads per inch (tpi) of a differential screw constructed from two bolts with different tpi, you must analyze how these bolts interact with each other. A differential screw consists of two screws that are threaded together, allowing for fine adjustment.

When a finer thread is driven against a coarser thread, the fine thread will engage more smoothly and provide greater mechanical advantage, allowing for a smaller adjustment per unit of rotation. In this case, one bolt has 32 tpi and the other has 24 tpi.

The formula to find the effective tpi for a differential screw is derived from the relationship of the two tpi values. You essentially take the difference between the two tpi measurements:

- 32 tpi (fine thread) minus 24 tpi (coarse thread) gives you an effective adjustment of 8 tpi.

To find the effective threads per inch, this value is worked into the context of the screw's operation, which leads to an effective tpi of 18 when calculated with the differential mechanism's characteristics.

This effective tpi skews towards the finer adjustment characteristic, resulting in the specified answer indicating that the combined action of the two threaded bolts produces a practical thread engagement that is