Which type of screw ensures a good grip without needing a drilled hole?

The type of screw that ensures a good grip without needing a drilled hole is a set screw. Set screws are designed to create a secure fastening by being threaded directly into a workpiece, utilizing the friction generated between the screw and the material it is driven into. This eliminates the need for a pre-drilled hole, allowing for a strong hold as the screw is tightened. Set screws often feature a hexagonal or square head, which allows for tightening with a wrench or a similar tool.

In contrast, wood screws typically require a pilot hole to prevent the wood from splitting, and their design helps them grip well in wooden materials. Sheet metal screws are not intended for materials like wood but for metal sheets, where they can tap their own hole but still benefit from being inserted into pre-drilled holes for optimal grip. Lag screws, while capable of providing strong fastening in wood, usually necessitate a pilot hole due to their thickness and course threads, which help to prevent splitting of the wood. Each of these other screw types serves specific purposes and applications that differ from the unique ability of set screws to hold tightly without pre-drilling.