Drilling a hole through a benchtop can be a bit tricky, especially when there are multiple materials involved. Here are a couple of options for you to consider:
- Starting from the top: If you use a regular holesaw to drill through the stone top, you can then use a Forstner bit or a hole saw for wood to finish the hole from the bottom. This way you can avoid using the diamond holesaw on the wooden underside, which could cause burning. But you will have to drill a pilot hole in the center of the stone first to start the holesaw. This method is less precise, but it will still give you a clean cut.
- Using a multi-material hole saw: Some hole saws are specifically designed to cut through multiple materials, such as wood, metal, and tile. These hole saws typically have a diamond-coated edge for cutting through harder materials like stone, and a separate edge for cutting through softer materials like wood. This might be the best option for you because it can cut through both materials neatly and you will only need one holesaw.
Regardless of which option you choose, make sure to use plenty of cutting oil or water to keep the hole saw cool and lubricated, and work slowly and carefully to avoid any damage. Let me know if you have any other questions or if there's anything else I can help you with.