Hi,
I recently got a 10"/5.6 Tele-Optar to use as a portrait lens on my 3x4 RB Ser. B. The lens was made to fit a Graphic lens board, but I hoped the screw threads would match. The diameters seem identical at about 48 mm. However, the thread on the lens is finer than the thread on the (fixed) lens board of my RB.
What I'm wondering is this: Is it be possible to have an adapter milled? If so, is this a complex (expensive) operation?
Any ideas would be appreciated. Thanks.

A good machanist such as SK Grimes should be able to do it but they are pricey.
The lens and lens board are measured in inches for both the RB Series B and the Wollensak lens. Use a caliper and measure the threaded section of the lens. Rounding up to the nearest standard fraction is common, .495 would be called .5 or 1/2 but I'm not sure that .7 would be rounded to 3/4. Look at the measuring threads on Grimes web site found under products then mount flange.

Now, take the lens and under good lighting and magnifaction as needed count the number of peaks of the threads on the lens. Next measure the thread distance of the lens, do not include blank area of the lens barrel. Now divide the thread distance by the number of peaks to get the thread dimension.
Take the RB and count the valleys in the lens board threaded area and measure the distance then divide the thread distance by the number of valleys to find the thread deminsion for the lens board.
I've been working on two tonight to figure out what size flange to look for. A Wollensak Vesta portrait from around 1912 has 6 thread peaks in .2 inches: .2 divided by 6 = .03 = 30 threads per inch (tpi), 1 divided by 30 = .03. The other lens a Kodak Anastigmat from 1942 has 5 thread peaks in .2 inches: .2 divided by 5 = .04 =24 tpi.

I think the adapter would have to extend beyond the lens board and hold the Tele-Optar just infront of it which might cause some vingeting.
Although the lens board is fixed to the camera one might be able to make a new one with the correct thread for the Tele-Optar and replace the lens board assembly currently on the camera. Graflex assembly techniques and manifacturing suggest that this might be a more cost effective means of mounting the lens. The lens board/front standard should be mounted to the bellows with screws making disassembly/reassembly easy. I am assuming a wood standard with metal clamps.