Wow,
I did not know I had these messages here...sorry all....been out of town..
Joaquin100...the answer is yes....the adapter lets you focus to infinity....here are the issues...1. Most of the G lenses do not work...due to the fact that the aperture is controlled by the camera....so I have gone to manual AiS lenses...I do have a few lenses that I like that are AF that I have to use on Manual mode..(not an issue for me...I like the older lenses...)
You have to take the SA mount off the camera and put the F mount on...so yes your SA lenses don't work....however, since the Sigma SD-14 are so cheap...I bought another one....I have one that is SA and the other is Nikon F....
Here a few threads you might find useful...
Let me know if you have anymore questions...
Avk and Robert....Ya I know the Geese are green....first attempt with the Nikon F mount on the SD-14....I just shoot with both eye's open and when I have what I want to shoot I take the shot...the Focusing dot in the bottom..does work too..however...I found due to the difference of lenses...and again these were not made for the Sigma...you get back and front focus issues....unless shooting Macro...this is probably my camera..and I know there is a way to adjust this...but found it easier to just do it the old fashion way....

...I always try to take two or three pictures...of the same subject....never fails that I move or it moves...Digital makes life so much better...The mount lets you use the camera just like the SA lenses...but only Manual.....
Hope this helps...
Let me know if you have any more questions....and sorry it took me so long to get back to you...
Tony C.