I built my first drag knife in 2000. It was developed for die cutting (inlayed) snowboard base graphics. Over the course of about a year and a half, I developed 2 different holders that were very effective in different circumstances. I set myself the goal of creating a new knife holder this summer that could do both jobs.
My new knife holder uses a standard irwin utility blade rather than an expensive custom blade. Having spent a bit of time looking for a commercial product, it came to my attention that there is a potential market for such a device. Tangential cutters are great, but far more expensive and not always necessary. I put together a second one that can be used for materials up to 1/8in (like cardboard and leather). Both holders can be used to cut a variety of substrates. I have used drag knives for cutting gaskets, snowboard graphics, leather, flexible magnet material and probably others. I have also used them to score ABS plastic to later be broken apart.
I am curious if others would be interested in such a device and what they might be willing to pay for one.