I was engaged in this alteration for the reason that my black Jupiter-9 1987 is too “fuzzy” on an open diaphragm.
It gave much more smaller sharpness, than my old Jupiter-9 under a Kiev photocamera.
I solved this problem having caught the high-quality optical unit of Krasnogorsk plant 1957 production, the release from Yury and replaced it in black Jupiter.
Of course,the regulation of a spacer for a new combination is required (lens/bayonet joint).
(comment ред: Floodlight-9 is one of the few lenses having a special ring spacer for focusing on infinity on the camera Zenith, as far as I know).
Holding a lens for a front rim the optical unit simply is turned off from a focus ring. There is no need to turn off screws. Here you damage nothing. Thus it can be set on Leica M3. It looks quite funny as Jupiter-9 and is much more normal lens 50/1.4.

jupiter9
I decided to leave a “soap” lens for photography of such old person, as I.
Again I received Jupiter-9 on M39 thread with an adapter on M42 from Yury. I received the no-lens adapter (there is no focus on infinity) from M42 on Nikon (price is $6) from Mike
Here that I managed to make:

Jupiter9M42
By arrow it is specified original ring spacer which gives focusing on infinity when the lens is set on the camera Zenith.

M42Jupiter9

Not changed Jupiter-9 of the Krasnogorsk plant (silvery) with M39-adapters,M42, M42 – Nikon. Red arrows specified a ring spacer, which it is possible to reach a focusing on infinity.

Jupiter9reshimmed
In this case the spacer isn’t reduced and now it is focused from macro to 9 meters.

1
On black Jupiter-9 there is a spacer allowing to be focused on infinity (together with fromt lens-block), and on Krasnogorsk it is deleted.

2
Here it is visible that the original spacer is ground off to the necessary size, allowing to be focused on infinity to black Jupiter-9 with a thread of M42 and the no-lens adapter.