M42-4-E-Var - A Focusing M42 to E-Mount Adapter

thingiverse

This is M42-4-E-Var, a focusing M42-screwmount to Sony E lens adapter / variable extension tube. It's a multi-part print ("mount", "spacer", "outer", "inner", "grip_and_retainer", and four "tabs"). If you prefer to spend several hours of print time, as much as a couple hours of post-processing/assembly depending on print quality and your expertise, and about 46g of filament, instead of buying something that does the job better, this print is FOR YOU! If you have a lens that needs servicing and you're afraid of trying it, building this adapter is very similar to re-assembling a lens, so this print is FOR YOU! If you want to learn how many manual lenses focus, this print is also FOR YOU! After you make this, maybe then you'll tackle your lens CLA, or avoid it like the plague (and focus with this instead of the ring that's too darn stiff on your treasured old lens). Disclaimer: Print and use this adapter at your own risk (which include but are not limited to the following: introducing small dust/PLA particles to your camera's internals, having prints break on you, having prints warp in extreme heat, having grease go where it should not, outgassing from glue, epoxy, and/or paint)! If parts print and assemble as expected infinity is guaranteed, and the helicoid should have over 10mm of valuable extension. When it's fully assembled the helicoid bottoms out at infinity and "tops out" on the "grip_and_retainer" focus ring, while having plenty of tab length, so it's my hope that it won't fall apart on you. I think the best use case for this adapter is as a platform to adapt small optics from film compacts and such, but it also works pretty darn well with small vintage primes! It feels a little rough/iffy with telephotos, especially if you can't support it while you focus. When adapting typical M42 lenses, the helicoid is always taking an unbalanced load - these PLA parts flex a bit and with enough force, unfortunately lubrication doesn't quite overcome the friction between the plastic parts. It's of course very sturdy when it's bottomed out or fully extended (and pressed against the retaining ring), but does have some slight play in between because the helicoid threads have the loosest tolerances. This adapter was tested with a wide variety of M42 lenses including Pentax Super-Takumars, Pentax Super-Multi-Coated Takumars, auto-only EBC Fujinons, automatic Helios and Jupiter lenses, Meyer Optik / Pentacon lenses, and various Made-In-Japan brands, including Mamiya-Sekor, Vivitar, etc. I've tried to make this M42 mount as universal as possible by making room for S-M-C Takumars' extra bits, Fujinons' aperture ring tab, and Mamiyas' outer tab also while providing a stop-down ledge for auto-only lenses. Thread alignment is more of a pain than I foresaw, but the rendered "inner" I included worked well enough for me and my lens stable - Fujinons thread past center, Takumars stop before it, and other M42 lenses land somewhere in between. I've also provided a way to help you sort rotation out for your lenses with a test print object and a file that lets you rotate the threads as needed.