My film slitter
There was a problem with the previous version in that the blades were extended too far from the cutting head, allowing the film to ride up on the blades and get caught on the non-cutting edge. The film then tore or became ragged on the edge. I modified the cutting head by seating the blades farther in the head so that only the cutting edge is exposed. Then I added velvet to the cutting head and the film channel to avoid scratching. The result is the film channel holds the film in a narrow gap and the film passes through straighter with no scratching.
For construction, I used an oak wood base, 0.5 inch thick and 4.5 inches long, cut to match the film width at 35 mm. For the remainder on the slitter, I used plexiglass (Lucite), 0.120 inches thick. I cut four identical pieces and mounted them to the base allowing 0.5 inch space for the blade holder. I cemented a plate of plexiglass on each side to hold the blade straight.
I used the same construction for the blade holder as in the previous slitter, except for the material, I used 0.5 inch thick plexiglass. I drilled the holes using a 0.250 inch brad point bit and used epoxy to hold the blades in position. This time, I also made a holder to allow a strip of Minox and a strip of 16mm to be cut from the same film at the same time. I started from the outside of the holder and spaced the blade hole 8 mm from the outside edge. After the blade spacing was determined, I placed the center blade and adjusted for optimum cutting.
The shape of the side plates matches the diameter of the film cassettes and the film is held straight by the inside of the slitter channel.
The final product of the slitting operation with the dual width cutting head. Actual film width is 9.1 mm for the Minox cut and 15.1 mm for the 16 mm cut. There is about 0.4 mm left on each side between the cuts and the sprocket holes.