Fujinon 135mm EX Mounting Thread

This lens won't mount on any of my existing boards and I was wondering if anyone out there had one of these beauties and knew the correct thread size for mounting this lens?

W.

A Fujinon brochure specs the thread as 53 mm diameter by 0.75 mm pitch. This is the same thread that Nikon used on an older version of the 150 mm El-Nikkor. Unfortunately it is a peculiar thread. Depending on the enlarger brand, lensboards were available years ago for the 150 El-Nikkor. Now, you may have to have custom machining done (e.g., S.K. Grimes). If you have the retaining ring, it shouldn't cost much to have the correct size hole bored. Or you can do it yourself. If you need threads machined, it will cost more.