I have a few paint tools, such as telescoping poles, that all use the same standard threads. Besides painting, I've seen the same or similar standards used for brooms, lightbulb grips, pool tools, and gutter cleaning poles.
Apparently there are two standards common in the USA, both based on a 3/4" dowel (0.75 inch or 19mm). One standard (shown here) has a pitch of 5 threads per inch; the other has 4 threads per inch. However, there is a LOT of variation due to the manufacturing of wood, plastic, milled aluminum, and cast aluminum tools on the market.
These objects are just the blanks, ready for combining into any other project. I've put in generous clearances, and a tapering thread at the shank end to help keep tools snugly fit regardless of thread sizing. I will post a 4-thread version too. Do any other global standards exist for these pole fittings?