Quote Originally Posted by David A. Goldfarb View Post
Pretty much, yes. Most enlarging lenses made since the 1970s for 35mm and medium format use M39 (Leica thread mount). For bigger lenses starting around 135mm, you may need a larger lensboard hole, and some short lenses designed for formats like 110 may have had smaller mount sizes.
Pretty much is correct, but you should be aware of some exceptions. The M39 thread is fairly standard, but there are other sizes out there. They require different lensboards. You also have to watch the back focus length (the distance between the back of the lens and the negative). Some enlargers will not focus using short focal length lenses like the 28mm Companon-S. Other enlargers do not have enough bellows draw to focus longer focal length lenses.