Which size reamer tip should be placed into the pilot hole to enlarge the holes?

The correct choice for which size reamer tip to place in the pilot hole to enlarge the holes is the smallest diameter. The reason for this is that reamers are designed to precisely enlarge existing holes to a specific size and improve the finish, so starting with the smallest diameter helps ensure that the initial cut is manageable and allows for controlled enlargement of the hole.

Using the smallest diameter reamer first reduces the risk of overcutting or damaging the material surrounding the pilot hole. This initial cut creates a guide for the subsequent larger reamer, ensuring that the enlargement process is both efficient and accurate. Once the smallest diameter reamer has done its job, a larger reamer can be used if further enlargement is necessary.

In this context, the other options—largest diameter, medium diameter, and equal diameter—would not serve the same purpose effectively. Starting with a larger size could lead to excessive material removal and poor hole integrity, while using a reamer of equal or medium size may not provide the necessary precision for effective enlargement. Thus, employing the smallest diameter reamer first is the best practice in hole enlargement procedures.