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[camz]

Does anyone know how to open the front group on the B&L Ic 5x7 lens? I know it unscrews from the front, but mine seems stuck.

Which lens wrench will work?

[disemjg]

Use a rubber tool; while a recent thread referred to a car tire I use a section of inner tube placed on my workbench. Press the lens into the bench/tube and twist, and pretty much anything will come free with this approach.

The only wrench that would be suitable is one of those rubber strap wrenches.

And be careful not to exert too much pressure on the diaphragm ring; they are not intended to take severe side loads and may be damaged.

BTW, the B&L lenses I have seen do not dismount beyond being able to remove the cells from the barrel. Each cell is crimped shut and cannot be disassembled. The front cell has a threaded engraving ring that you can assme is frozen in place; none of mine will budge. Thus you will not be able to clean the internal surfaces the way you can clean a Zeiss lens. Only the outer surfaces of each cell can be cleaned.

[disemjg]

I just realized that CAMZ already has the cell out of the barrel, and my first parpagraphs were not needed.

The last paragraph speaks to the issue, and as I said all the ones I've had were frozen. The B&L lenses have an aluminum cup, and I think the ring is also aluminum. That is a bad combination, as AL on AL tends to seize over time. The surfaces are painted but that may not prevent the seizing. It also does not help that there are no spanner slots, and the only "enhancement" to grip the retaining ring is the serrated edge. That edge is usually flush or below the edge of the cell cup in any event, and cannot be reached.

So if you have to make a determined effort to get the ring off, try the rubber tool trick on the ring. Cover the front element with some masking tape to prevent its being marred during the wrestling match you are about to have with the lens. Then you need to come up with a tool to reach the face of the ring without touching the front element. My favourite source for this is my tool box, where I find several racks of socket wrenches whose various sizes offer a good chance of finding one that fits the bill. Lens + rubber sheet + socket may equal removed ring, but there are no guarantees.

Also, before trying to get the ring loose, apply some penetrating oil on the ring threads and let that soak in for several days. Be sure to remove all traces of the penetrating oil from the ring before trying to remove it. You may also have to resort to heat cycles with a torch to break the bond between the ring and the cup.

The lens may win this one.

[ This Message was edited by: disemjg on 2006-12-23 12:08 ]