Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3993003.
This adapter allows you to use 18v Makita batteries in 18v Ozito/Einhell tools. The fit is close but not tight, so that the adapter doesn't move around in the tool or battery but also does not bind.
To complete this print you will need some 1mm thick copper sheet (I flattened a copper pipe which had 1.2mm thick walls, after flattening the thickness was about 0.9mm.) and you will need to solder the copper together as seen in the photos. I have included a sketch of the shapes that you need to make. Make 2x of each shape per adapter. The 21mm length is the one that gets bent to receive the tool contacts. The cheapest way to cut copper sheet is probably with a pair of tin snips.
This will likely need to be printed in something more flexible than PLA. I printed in ABS but PETG should also be suitable.
I have included two versions, a one piece version and a 2 piece version. The 2 piece requires less support material but does need to be glued. I prefer the one piece version.
Thanks to whity and sportssedan for their original designs. whity's Makita adapter is fantastic but was too tight to fit so I have adjusted it and cut some holes for the contacts. I took inspiration from sportssedan's Ozito adapter design, especially the latch but I made it more flexible and all around bigger for ease of use and positive locking.
As a side note, I discovered the hard way that Aluminium is very hard to solder and had to change to copper which was much easier to work with. You can find 1mm copper sheet online, however you can also split a copper pipe and flatten it out if you have trouble sourcing a copper sheet.
Edit 28/04/2020: I made thte catch slightly taller and printed in PLA. Can confirm that PLA works fine.
Edit: 21/07/2020: I have added a version with a 35.5mm gap as requested by Kingphil18