I'm about to mount a Schneider Tele-Xenar 360mm F5.5 in a compound shutter on a Toyo 45A lens board. The lens was originally fitted to a Technika 70 board by an extension tube and 6 small screws. I'd prefer to mount it conventionally. The fixing ring needs to be about 60mm across, so it is not a Copal 3 size. In trying to track down a suitable ring, what size should I ask for?
Take the flange off the T70 board. Mill a hole the proper size for the len's threads to fit through on the Toyo board and place the flange on the back of the board and rotate the shutter till tight. You can have a machinist cut off the mounting holes on the flange by milling it down if you really don't want to mount the flange to the board. BTW, why not just mount the flange to your Toyo board?
If I could have obtained a mounting ring and mounted the lens conventionally, I thought it would better distribute the weight of the lens. Using the flange the weight would all be forward. Looking it it again I think I will mount on the flange as it was on the T70 board. I will be using a Toyo board with a '0" hole, and enlarging it. I can't get blank boards here, only pre cut ones. First I will use a compass to mark out a circle on card that will just fit within the lens board hole. I'll place the board over this circle, and tape into position. Then using the same compass pin hole, draw another circle on the lens loard to the dimensions of the old T70 one, it should then be central. I'll then score the circle with dividers. Then I intend to drill a series of holes just within the scored circle, pop out the centre piece, then slowly file it to size with a half round file. Then line up the old T70 board to mark out the 6 holes for fitting the flange, drill and countersink them. Previously I've cut many a similar hole in aluminium to mount meter movements etc in electronic/radio projects, so I don't anticipate any problems.
Sell the Tech 70 board on eBay with mounting tube for the 360/5.5 Tele-Xenar intact, and you'll probably make enough to order a custom flange from S.K. Grimes and have it mounted on the Toyo board and have cash left over. See if www.mpex.com or www.lensandrepro.com has the correct flange for that shutter in a box somewhere, and you'll have even more cash left over.
I knew I wrote this down recently - it's here: http://largeformatphotography.info/lfforum/topic/500154.html
In short, M60 x 29 1/2 tpi.
Typo there, the ring is M60 x 29 1/13 tpi. SK Grimes has the ring.
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