**There is likely no pre-existing adapter that will do what you need.** The [Flange Focal Distance][1] (FFD) of MD mount is 43.5mm, while the FFD of EF mount is 44mm. That's only 0.5mm for an adapter without optics. For a *hypothetical* adapter with optics, you'd likely be multiplying focal length by 1.4x, so 85mm → 128mm.

**The feasibility of modifying the lens depends on its specific construction and design.** Although there is no aperture or autofocus mechanism to complicate conversion, I personally would not try, unless the lens was particularly cheap, like less than $10.

* **Converting to M42 is *not* as simple as just cutting threads into the existing EF mount** because the FFD of M42 is 45.46mm. Ordinarily you would need to shorten the lens by 1.46mm. Given the apparent design of the mount portion of the adapter, based on examination of the photograph in your question, it would not be possible to just shave the barrel down. However, since the lens is available in Nikon F mount, the built-in focusing mechanism probably has enough "play" to allow infinity focus after altering the mount.

* Another option is to **cut off the threads and drill screw holes into a thin lens reversal adapter for MD mount.** Since FFD of MD and EF are similar, the lens would likely still focus to infinity, though it would lose some of close focus.

Rather than "throw good money after bad", **I would opt for a different lens.** There are other lenses that are known for producing swirly bokeh, such as those in the Helios series. I have also encountered other lenses that produce mild amounts of swirly bokeh that are most noticeable when there is foliage in the background. You may even already have one without having previously noticed the swirl.

**See also:**

* https://photo.stackexchange.com/q/62000/75526
* https://photo.stackexchange.com/q/105926/75526


  [1]: https://en.wikipedia.org/wiki/Flange_focal_distance