Given their legendary reliability, you’d think you could run your worm-drive saw forever without any maintenance, but that’s not the case. Worm-drive saws need their gear-oil changed regularly because it gets dirty through use. Once it’s sufficiently dirty, it’s lubricating ability is compromised and the internal gears will wear out faster than they would with fresh oil.

Before you decide you need to change the oil in your saw, you first want to be sure you have a real worm-drive saw. Some people mistakenly call rear-handle saws with a hypoid gears a “worm drive,” like Makita’s 5477. The confusion is easy to understand, as hypoid and worm-drive saws are configured similarly, with a rear handle and a motor parallel to the blade. However, hypoid saws, like sidewinder circular saws, have sealed bearings that don’t require any maintenance.

In this video, Tool Tech host Patrick McCombe shows how to identify a worm drive, explains the recommended oil-change schedule, and shows you how to check and change the oil.

Senior editor Patrick McCombe has been testing power tools on behalf of national publications for more than 15 years, and he regularly meets with product manufacturers to try out new introductions. In the Tool Tech series, Patrick reviews the latest tools and materials, discusses building technology, and shows time-tested techniques for better, more-efficient home building.