Cutting the Uncuttable
In the early 1990’s, we were approached by a company supplying tools to the manufacturers of Kevlar. Kevlar is bullet and stab resistant material and poses a singular problem for most scissors, in that it is designed to resist attempts to penetrate it.
This substance is produced as a polymer and spun onto huge spools two metres high. The full spools are worth thousands of pounds, and when the spool is full, the fibre has to be cut and a new spool started. If this process is slow (if people are hacking and hacking to cut the thread) then fibre is wasted and sometimes the production has to stop and time is lost. So it’s vital that the thread can be cut safely and quickly, and production can run uninterrupted.
We were asked to solve this cutting problem, which we did by trial & error – and the factory was happy! However, Kevlar is very aggressive to scissors and they don’t last much above a week. The scissors can’t be resharpened either, but to explain why might bore you to death….
Some years after this, when new types of polymer materials were arriving on the market at a rate of knots and we were trying to get our scissors modified to meet these demanding operations, we approached the Sheffield University Department of Engineering Materials who were most accommodating and very helpful with all this. They asked if we would allow one of their Masters students to do a project on how we managed to get our scissors to cut Kevlar and we were very happy to oblige!
Lots of tests were done, with electron micrographs taken of the cutting edges and so on which were very interesting – under the huge magnification, the Kevlar cutting edge looked as if it had been curled back by being bashed with a hammer; the Kevlar sample was ragged and mangled, but cut! They couldn’t work out how the scissors cut the Kevlar, so we now call it a black art.
Believe it or not, there’s a substance even harder to cut than Kevlar called Dyneema, which we also provide scissors to cut. With different modifications, our 10” black sidebent scissors can also cut carbon fibre, glass fibre and mixtures of the two, and are in ever increasing demand.
Every pair of these scissors is tested on the material it is designed to cut, so we have to buy the materials in. For a time we bought the Kevlar from a bullet proof vest manufacturer, and the material sometimes had mangled bullets in it!
We are sent samples of materials and ‘stuff’ on a weekly basis for us to provide the best scissors to cut them, as we are known as solvers of cutting problems.