!!!! WARNING !!!!
This is a quick but well working solution for lenses mounting and macro photography. Threads working with standard 52mm, 42mm, 37mm (not tested yet) accesories, lenses and spacers and you won't meet any problems with that. Still (3 rings set with bayonet fittings costs 5$ on ebay) Do not trust plastic for expensive or heavy lenses, if so you do it at YOUR OWN RISK!!!!
It's a set of rings which i designed for a replacement of BeastGrip's DOF adapter. The main body is 60mm ID and 62.6 OD with 3 main rings 36mm, 20mm,12mm plus a 42mm to 60mm adapter, a 60mm to 52mm adapter, a 52mm to 37mm adapter and a 12mm 37mm spacer. Not all needed for the adapter but i designed them anyway.
The threads for 60mm, 52mm, 42mm are tested and working amazingly with a tight fit on each other and components. The 37mm rings are not tested for accuracy, i'll come back to that to confirm or correct once tested. Missing the internal focus screen holder from the set, will be uploaded as soon as i make some modifications.
For the first time you have to clean all the female thread starts (bottom sides when printed) with a knive to remove any access plastic in a 45 degrees angle so you won't destroy the inner threads. Go easy on the first attempt on putting them all together.. (needs patience) once you start screwing it straight, screw and unscrew a bit. Use this technic tightening a little more every time till you have it screwed all the way.
The rings are strong enough and might hold heavier lenses (than my helios m44) allthought as i wrote in the beggining you are using it at your own risk.
Hope you'll find it usefull!!!
If printer is callibrated correctly you won't meet any issues. Support is needed especially for the adapter with different threads but i used them in all pieces for a clean edge. A little knive cleaning job on the internal edges that face the heat bed will be needed in 45 degrees angle to not harm the threads, and at the external side also. Printed with PLA with 210 nozzle, 60 heatbed.