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Cutting the Uncuttable…

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We left the previous blog at a point where I was discussing the uselessness of cheap scissors, with those attempting to cut Kevlar being a case in point! In the early 1990’s, we were approached by a company supplying tools into 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 (2m high) and when the spool is full, the fibre has to be cut and a new spool started. The full spools are worth 1000s of pounds. If the process of cutting off and starting a new spool is slow, ie people hacking and hacking to cut the thread, then fibre is wasted, sometimes the production has to stop, and time is lost. So it is vital that the thread can be cut safely and quickly and production can run uninterrupted.

We were asked to solve this cutting problem, and we did by trial & error and the factory was happy!

The Kevlar is very aggressive to scissors and they don’t last much above a week…..

They can’t be re-sharpened as – oh well it would take too long to explain why without boring you all 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 and 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. There is another horrible material called Dyneema, harder to cut than Kevlar, which is cut by other means. With different modifications, our 10” black sidebent scissors will also cut

Carbon Fibre, Glass Fibre and mixtures of the two (picture below) 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! See pictures below.

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.

Kevlar & Bullet
Kevlar & bullet close-up
Kevlar & bullet test situation
Carbon and glass fibres weave

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.

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