Film Slitter Design Considerations
I have a friend that owns a machine shop and takes on special projects now and again. I was talking with him about making a film slitter for the Kodak 70mm infrared film, and he's willing to help out. Now I know there are two folks who cut and respool this exact film in 120.
I've purchased from one of the two individuals in the past. Unfortunately, it appears, and I've confirmed this with him, that with his slitter he has to pull the film through it. This has produced a number of very fine scratches over the length of the film. He did offer to replace what I had left, but since there are only two rolls, I didn't bother with it.
I was wondering if anyone knew of a site that deals with the design of film slitters? I'd like some design considerations for a design that doesn't require pulling the film, but secures it in place while one runs a slitting blade the length of the film. I do love the Kodak infrared film, as it always had that glow about it, and 120 was a usable size. Thanks in advance for your thoughts.
You might check out Minox related sites for ideas. Minox users often cut down 35mm film and respool it.
Film slitters are often (a relative term) used to split 35mm film into narrower widths for subminiature cameras (16mm, Minox). Most are jerry-rigged affairs for low volume use but many years ago Minox made one with a handcrank. Common issues are scratching of film and film "chips". Notwithstanding the film size, I would assume the basic issues are the same regardless of width.
You might try a search looking through www.subclub.org or a search on "Minox and splitter". Here are some links on the subject that I have:
Also, there is an individual who sells film split for Minox and 16mm (http://www.subclub.org/sponsors/goathil2.htm). He might be able to shed some light on the subject if you contact him directly.
there a person by the name of ray papalis who builds film slitters for submini-camera users (like the minox david goldfarb mentioned). he makes them out of hardwoods are they are beautiful. i know of people who use them to cut down 35mm film to re-load into 16mm and 110mm ( and minox) cassetts.
mr papalis used to have a link from "the sub club" ( submini website ) but it isn't an active link anymore. there is info on these pages regarding building a slitter ... http://kcbx.net/~mhd/2photo/slitter/build.htm
No silver bullet for you, but I've had good results with a slitter made from a 120 Spartus Fullvue pseudo-TLR. The important thing is to protect the film where it's under the most tension between the blade and the take-up spool. I did it by trimming away the relevant plastic just enough to ensure a straight path from the supply side (which has a handy roller bar) to the take-up spool.
There are flatbed designs, but they might be subject to more wavy cuts due without a blade guide on the other side of the film. I use a patch of closed cell foam to anchor the end of the blade. I got a wavy cut once, which may have been due to unstraight loading and having to crank, crank, crank instead of continuous pulling.
In any case, having a sharp blade is important. I use the threaded rod and nuts/washers to position the blade.
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Only advice I can give is that in the coating plant where I worked one summer they used scalpel blades (the surgical knife) in the slitter....
At Kodak, we used a small hand cranked or machine run version that used no blades and did a very fine job cutting film and paper into the desired widths. It was adjustable from 16 mm to 35 mm to 4" etc for small jobs.
It used grooved rollers that punched out a small strip of unused film between strips of 'good' film. It was like a set of matched square waves made of stainless steel. Very efficient.
Sounds like the machine I use for making fresh linguini, but mine has nylon rollers.
Originally Posted by Photo Engineer
Film is very abrasive, but I've had good luck with ceramic blades. My first attempt used the broken point of a Kyocera kitchen knife, my final (so far) version uses two tiny points from ceramic envelope slitters that I got from an office supply store that run on a threaded rod in a polyethylene carriage made from one of those white cutting boards. Works great! And it is safe in the dark. (Just realized that I have a tendency to mis/re-use kitchen items...)