Nikkor-W onto a Sinar lens board

[cluttered]

I've previously mounted several different lenses to Sinar lens boards as well as Linhof-compatible ones, but this particular one has me baffled.

The lens is a Nikkor-W 300mm 5.6 (copal 3 shutter), and I'm trying to mount it into a Sinar lens board. I've got the front element, the shutter, and the rear element, plus a flange and what appears to be a spacer ring. The problem is that I can't mount the lens to the lens board without about a millimetre of free play. It appears as if the spacer ring is too small for this combination, but maybe I'm just doing it wrong.

So I unscrew the rear element from the shutter, place the front element plus the shutter face-down on the table, put the spacer on top of that, and then the lens board on top of that, and then try to screw the flange into place with the aim of securing the lens board to the back of the shutter. But if I do this, even if I screw the flange all the way in I have about a millimeter of free play between the shutter and the lens board. It's as if the spacer ring (between the back of the front element and the front of the lens board) is too small, or I'm missing a second spacer between the back of the lens board and the flange.

So am I doing this wrong or am I missing something? I bought this lens a while ago but haven't tried to use it until today.

This is the first time I've tried to mount a copal 3 shutter (all my others are either copal 0 or 1), so maybe there's something different to how it's done compared with copal 0/1.

[fishbulb]

On my Nikkor w 360mm f/6.5, it goes: front element and shutter face down, lens board, spacer ring (on top of back side of lens board NOT through the hole in the lens board) then the threaded ring to tighten it down, then the rear element. Just took the lens apart and checked. If the spacer ring is falling through the lens board hole, then the hole is probably too big and not actually copal 3 size. Also I am using a sinar board.

[cluttered]

I tried that combination (ie, having the spacer on top of the lens board as I assemble it), but it ends up much the same. The spacer ring isn't falling through, but it's as if it is just isn't "thick" enough.

Or maybe my lens board is too thin? It's a no-name Sinar-compatible lens board, it looks to be about 2mm thick, but my other Sinar lens boards seem to be a bit thicker. I've only got the one copal 3 board, I'm tempted to try to find a different one somewhere...

[fishbulb]

Measured the hole? Copal 3 should be 65mm exactly or a bit over 2.5 inches. About 2mm sounds right for the sonar board thickness. But thickness shouldn't matter; I have mounted my 360mm on a much thinner toyo board.

What happens when you tighten down the retaining ring? It just runs out of threads and stops, not tight enough? Would the problem be solved by a thicker spacer?

[cluttered]

I've measured as accurately as I'm able, and the diameter does appear to be exactly 65mm, and the thickness is about 2mm.

Yes, when I tighten the retaining ring it does run out of threads and stops about a millimeter short of where it needs to be with this spacer. So I think I'd need to do one of three things:


Use a thicker lens board (but it sounds like mine is the right thickness), or
Use a thicker spacer, or
Use a second spacer (one on each side).


So I'm still not clear if I've bought something that's not quite right or if I'm just simply doing something silly.

Thanks for your help, you've helped me rule out some options. I think I'll try to find something in my boxes of parts that I can use as a quick-and-dirty second spacer.

[cluttered]

Well, I've not been able to find anything that I could use to improvise a solution.

Does anyone know if I can buy an extra spacer ring somewhere or maybe a "thicker" lens board, or some other inexpensive solution?

[Louis Pacilla]

If and when I run into this I put one trimmed piece of gaffers tape on the back side over the hole & then cut the hole out. I then put 1)shutter 2) spacing ring on the front side of the lens board then the 3) retaining ring goes in the rear. I tighten the retaining ring by hand moving it's position until I can tell that when tightened up all the way the shutter position will be correct. To finish up I tighten it up by holding the shutter (w/ out damaging any of the external parts) and turning until fully seated. The gaffers tape w/ both make up for gap & will add friction so holding the retaining ring and that keeps it from spinning.

[cluttered]

If and when I run into this I put one trimmed piece of gaffers tape on the back side over the hole & then cut the hole out. I then put 1)shutter 2) spacing ring on the front side of the lens board then the 3) retaining ring goes in the rear. I tighten the retaining ring by hand moving it's position until I can tell that when tightened up all the way the shutter position will be correct. To finish up I tighten it up by holding the shutter (w/ out damaging any of the external parts) and turning until fully seated. The gaffers tape w/ both make up for gap & will add friction so holding the retaining ring and that keeps it from spinning.

That sounds like an ideal solution, I'll definitely try it. Thanks!