What tool is primarily used for preventing excessive wear on machine ways?

A lubrication system is crucial for preventing excessive wear on machine ways. Machine ways are the surfaces along which components move, and they can be subject to high friction and wear due to movement and load. A lubrication system provides the necessary oil or grease that minimizes friction between these surfaces, allowing for smooth operation and extending the life of the equipment. Proper lubrication reduces the chances of overheating and damage to the machine, resulting in better performance and reliability.

While a grease gun is a tool that can be part of a lubrication system, it is not the comprehensive solution sought in this question. A cleaning brush, though essential for maintaining cleanliness and ensuring proper adhesion of lubricants, does not directly prevent wear on machine ways. An adjustment tool might be used to align components for better functioning, but it does not address the lubrication aspect critical for reducing wear. Thus, the lubrication system stands out as the primary tool in maintaining the integrity of machine ways.