How to open B&L 6 in. Lens?

[Jon Shiu]

I picked up this old B&L 6 in. lens and want to clean the inner surface of the rear element. However, it seems neither the front, nor back group will unscrew. There are 3 set screws around the body. There are retaining rings for the front and rear elements. Any tips?

Jon

[Kevin Crisp]

You are saying the rear element won't unscrew from the body of the mount? If I had this situation I'd try my rubber cones on the retaining ring first. That works about half the time. If the slotted retaining ring by the glass is too stuck for that, SK Grimes wrench with the slotted tips.