A small disk sander is a useful and cheap addition to the shop. For about $100, you can buy a cheap combination 6″ disk/belt sander that’s extremely useful. The size and cost of power tools ...

Cut each disk about 3/8-inch-thick using handsaw or power miter saw. Then, sand each side smooth with a disk sander or belt sander. Once you’ve cut and sanded several disks, ...

Cut a disk with a 30-centimeter diameter. You can craft your Secchi disk from just about any material, including metal or wood, though plastic is most common as it’s often easier to cut to size.