I recently got a Nikon D3400 and an old auto Sicor-XL lens and wanted to use both. Only problem is that they don't use the same mounting system. Which lens adapter can I use for my D3400 with a Sicor-XL?
Here are some pictures of the lens:
The mount on this particular lens appears to be an M42 threaded mount.
Because the Nikon F-mount's 46.5mm flange focal distance (FFD) is larger than the M42's 45.46mm FFD, you can't use a simple adapter to mount this lens to any Nikon F-mount body and have it work as expected. The lens would need to be about 1mm inside the Nikon's body to work as expected.
M42 lens to Nikon F mount adapters exist, so you can physically mount the lens to your Nikon body. But because of the FFD mismatch, you will lose the ability to focus at infinity. In fact, depending on the focal length of the lens (your pictures don't show the focal length), you probably won't be able to focus more than a few meters away. But if you only want to focus on closer objects, this lens adapted to your Nikon will work fine.
See these related questions here for more information: