Yes, the Kalawen bottle cutter can cut the bottoms of jam jars. This tool is designed to cut glass bottles of different sizes and can be adjusted to accommodate various diameters, making it suitable for cutting the bottoms of jam jars or similar glass containers.
The Kalawen glass cutter set is mainly designed for cutting glass bottles and other round glass objects. It is not suitable for cutting smooth glass or mirror surfaces as it has been specially developed for cutting round surfaces.