Two lens mounting questions

[chrism]

This is harder than expected! I have acquired two lenses, but both have a mount problem. The first is a huge and heavy Symmar 360mm, which has no retaining ring. Any source for such a thing? S K Grimes?

The second is a Nikkor-M 450mm, and despite using a proper lens spanner, I can't loosen the retaining ring at all. Even then, there is an extra ring for lens extension tubes, which I don't think I will need on a 10x8 camera, and which is larger than the 65mm hole in my lens board for its Copal #3 shutter.

Again, I'm wondering if I hadn't better just ship both of them to S K Grimes. Unless any of you clever folks have easier solutions?

Chris

[EdSawyer]

Pics would help. Many copal 3 sized lenses have a spacer/centering ring to deal with different lensboard thicknesses. These should be easy to mount, no need to spend months at SKG for this.

[chrism]

Here is the Nikkor-M, showing the threaded mount for the extension tubes. The rear half of the lens doesn't protrude, unscrews easily, but the retaining ring after that is stuck fast. I guess I could mount the flange of the extension tube onto a lensboard, even though I think I have bellows enough for this lens without the tubes.



If I do that, I have to confess I don't know anything about flange mounts!

Chris

[Jim Noel]

You might try removing the rear cell and placing it in the freezer. Once good and cold, you might be able to unscrew the offending ring using two rubber pieces made for removing difficult jar lids.

[chrism]

I'll try that.

I did find a retaining ring for the Symmar-S at BHP.

[EdSawyer]

sometimes a heatgun also helps loosening stuck rings. Also, try a rubberized strap wrench, that will help apply torque and pressure evenly. (actually use 2 strap wrenches, one to counter-hold the shutter body...)

[c.d.ewen]

Jim's advice is the first thing to try, then Ed's. Try and just heat the ring evenly a little bit and then see if it'll come off. I wouldn't put a strap wrench onto the shutter, as it's plenty big enough in your hand.

Given that it's not a precision surface, I wouldn't hesitate to use a pipe wrench on the extension, although I wouldn't do it all hand-held. Put the wrench in a vice and make sure you have a good grip on the shutter. Don't use too much force, and watch out you don't bend any of the levers. If you don't get it off after the first try or two, give up and send it to Grimes.

Charley

[EdSawyer]

Good info from Charley. It should be possible to remove this without machining it off, hopefully.

[chrism]

I'm afraid neither heat nor cold undid the Nikkor-M 450mm, so I have flange mounted it with four bolts onto a lens board. I used three layers of black cartridge paper as a gasket to make it light tight. Used it for the first time today with just the 40mm extension tube that is permanently attached to the flange. This let me focus at infinity, and I assume the other tubes, if used, will help closer focussing (though I don't see any advantage over cranking out the bellows).

Still waiting for the retaining ring for the Symmar 360mm.

Chris

[jb7]

If you can get a good grip, they should come apart- easier said than done though.

Regarding the missing ring, is the symmar in a Copal 3?
There might be an inexpensive answer here-