Contax RF / Kiev / Nikon RF mount adaptors...

Purchased a Kiev (Contax/Nikon) to Fuji FX adaptor from that auction site recently, I have to say I'm a little dissapointed. It's essentially the focussing helicoid and mount from a Kiev shoved into a LTM39 - FX adaptor, which is about what I expected I guess.

So I suppose it 'works as intended', it holds the lens and allows focus. Sadly, the infinity is way off, at around 3 metres on the focus scale and there is no minimum focus stop, meaning the lens can be unscrewed right off the helicoid. Overall it's rather sloppily put together, which is a shame, as it could be so much better.

So ideas...

I'm going to play around with some shims until I get the infinity focus right, then I'll see if I can get a precision shim piece made on the works 3D printer, to both set the infinity focus and centre the lens in the LTM39 ring, hopefully a nice snug fit will also make it good and light-tight.

So, my real question is, how can I create a "stop" to prevent the helicoid from unscrewing completely? Any ideas? Ideally in such a way that I can still use the external bayonet to mount larger lenses, though I'm not sure of the weight of a larger sonnar hanging on 3 tiny set screws, so maybe this will be for internal bayonet lenses only, which would simplify matters a bit.

Also, any ideas as to how I can 'tighten' the focussing action a bit? It's rather too easy to turn, as I'm guessing that on a 'real' Contax/Kiev, the rangefinder gearing provides the damping required for a nice focussing action.

Shame, particularly as the Helios-103 that came with it would appear to be a rather good example.

My goal is to try and create a digital replacement for my much loved Kiev-4A, the Fuji X-E series bodies have the right heft and mechanical, tactile, feel to them, it's just the lens adaptors where it all falls down...

Wouldn't it just be cheaper and easier to buy M39 fit lenses?

I have a Jupiter 8 (50mm f/2) lens that I use on a Sony a6000 via an M39 adapter. It's an excellent lens with its own focussing helicoid and no usage issues.

The lens cost me £20 (about $28 US), which was less than the cost of the Sony E to M39 adapter.

Where would the fun be in that?

I do have some LTM39 lenses, along with nearly the entire range of Zenit M39 SLR lenses, but I like the oddness of the Kiev/Contax system.

Besides, the Helios-103 is unique to the Kiev/Contax mount.

Fitted my 3D-printed shim today, needed a little adjusting, but it's a very snug fit. Infinity looks to be about as close as I'll get it without resorting to shimming 0.05mm at a time.

Not a bad look on the fuji. A few quick test shots suggest everything is sufficiently parallel and centred for real world use, I'll give it a go at the weekend.

Helios 103 at around f4, improved 3d-printed Kiev/Contax mount adaptor, Fuji X-E1, out of camera jpeg, resized only

I think I'm happy with the way that works.

"Helios 103" NOW, we're talking! It's said to be a Soviet version of the Summicron, although I think the "prototype" is the Zeiss Jena Biotar.

I have shot comparisons of the Soviet lenses to Canon, Zeiss, and Leica lenses in various posts here on Canon and Contax RF bodies, and in real situations they are surprisingly equivalent.