I am looking for right-angled metal cubes, with one vacant face to allow for concentric nesting, their tight tolerances allowing them to slowly sink under the force of gravity.

Although CNC milled options would achieve this, are there any cheaper manufacturing methods ?

Manufacturing is one expense, and making them to fine tolerances is another. Accuracy cost money. You got the high and low tolerance meanings the wrong way. 'Low tolerance' is the high accuracy stuff.... as in having a low tolerance for errors.

Edited October 28, 20223 yr by StringJunky

Just testing