After some testing, it was doable. I could get infinity focus with EOS to DKL adapter, plus the 52mm filter ring that goes on the rear of the adapter, plus the Yeenon 18-33mm focus helicoid. So I started doing it but forgot to take pictures of the process. But, it's very easy anyway. Here is what you need:
- EOS-DKL adapter (M42-DKL will also work, and gives you a few millimeters more space to work with, but the mount to the helicoid will have to be modified)
- J-B Weld or J-B Kwikweld or similar epoxy. J-B Kwikweld is my favorite. Canadian Tires sells them in the automotive section with other welding materials, NOT in the glue section. It took me a while to find it and many store clerks had no idea what I was talking about when asked for it.
- A thin rim 52mm filter. Remove the glass from the filter. The thinner the rim the better. If this filter ring is too thick, you may not be able to focus to infinity. So test it first.
- 18-33mm Yeenon focus helicoid (other similar range cheaper equivalent). Helicoid should have a 52mm opening on the lens side. On the camera side, it should have a NEX mount.
EOS to DKL Adapter. Click for larger
First thing first. File the three bayonet blades (in red) on the side of the EOS-DKL adapter until the rear of the mount is all round. The picture below is not an EOS-DKL adapter but an M42-EOS adapter, but the principle is the same. A Dremel grinder is invaluable here and it would only take a few minutes.
File/Grind the bayonet blades (penciled in red). click for larger.
Once the blades are filed/ground, try putting the 52mm filter ring over the rear of the adapter. It should fit near perfectly. Take the filter ring out, and clean it, as well as the rear of the adapter to make sure no oily residue is on it. After both are dried, apply epoxy to the inside of the filter ring, and put on the rear of the adapter. Put the adapter face down on a level surface, and put on a heavy weight on top of the filter ring to ensure the epoxy will set with the ring perfectly flat and even. If you use J-B Kwikweld, it will set in under 10 minutes and cure in about 6 hours.
Happy together. Filter ring on the rear of the adapter. click for larger.
Once the epoxy on the EOS-DKL adapter is cured/bonded, screw it onto the focusing helicoid. Attach your favourite lens, and enjoy the close up capability! Next time I will post some comparisons with and without the helicoid.
With Yeenon helicoid and lens attached. click for larger.
A final note. You can do this with a different mount, like the EOS to EXA (Exakta) mount. In fact, that will be my next project. This time, I will make sure I take pictures of each step.