A Long Week’s Journey Back to Machining Mitchell 46

As there has been nothing simple about bringing Mitchell 46 back to life, it is only fitting that the process of getting the camera securely mounted to the milling machine, and true and parallel to the film plane, was a week-long endeavor. This process had to take into consideration machining the bottom surface of the camera so the aperture ends up parallel to the lens mount, as well as being at the correct flange focal depth. Additionally, it must be centered to the film plane’s north, south, east, and west positions. As there are only 2 factory machined surfaces left on the camera that I can indicate to, the magazine mounting position, and the lands that the film transport registers to, the setup on the milling machine had to allow for accurate adjustments in 4 planes. To begin, I selected a precision right angle jig plate as the starting point so the camera was at a true 90 degree angle to the machine table. Then I assembled a stack of 1,2,3 blocks and parallels so the magazine mounting surface on the camera could sit on the parallels.

This gave me two reasonably accurate planes to begin the indicating process from. A piece of threaded rod was placed through the angle plate, and a capture plate on the operator side of the camera was used to clamp everything to the angle plate. A sacrificial adjustment plate was put between the angle plate and the camera casting, and I added screws to the four corners of the angle plate as adjustment jack screws.

The next step was to indicate the surface that the movement mounts to, as well as making sure the camera casting is level front to back, so that after machining the replacement bottom plate, the aperture will be true to the L-base. I flycut the surface of the replacement bottom plate so that it was flat and the overall height of the camera from top to bottom was correct. Then I machined the mounting surfaces for the front and back dovetails. As there are so many variables here, I made the decision to stop at this point so that I can rough-assemble the camera casting on the rackover L-base and make sure what I have done so far is correct. That, and I needed a nap!