How to cut ropes

PPE ropes for mountain sports and work safety uses are usually produced by the manufacturer with a specific length. During this process, the ends of the rope are ultrasonically welded and labeled.

In many practical applications, however, ropes and cords also have to be regularly cut by the users themselves. This Knowledge Base article explains how ropes are cut and, above all, how they can be permanently sealed to prevent them from fraying.

The work described below should be performed outdoors, with the use of extraction equipment, or, as a minimum, in well-ventilated rooms. When melting and bonding synthetic fibers, toxic vapors are generated that should not be inhaled. In addition, heat-resistant gloves, ideally thin leather gloves, should be worn. The work should also be performed on a heat-resistant surface.

The process of cutting a rope always starts with stripping the last meter of rope. This makes the sheath sit firmly on the core. If the core disappears into the sheath while stripping the rope, sufficient clearance must be left when making the cut to ensure that the entire core is available at the point where the cut is made.

The next major challenge is that of the material composition. In the case of most ropes and cords used as personal protective equipment (PPE), both the sheath and the core are made from polyamide 6. This can be easily melted and thus sealed. The best tools for doing this are special rope cutting devices, which are essentially just soldering irons with a cutting blade.

First, the hot cutting device’s flat blade is used to smooth down the sheath in the intended cut area so the sheath yarn fibers melt to form a transparent surface. The rope is then severed by applying light pressure with the pre-heated blade. The resulting burrs can be smoothed down with the blade.

Anyone who doesn’t have a hot cutting device can use a Bunsen burner, camping stove, or lighter instead. In such cases, start by stripping the rope and melting the sheath in the intended cut area over the flame until it is smooth. A carpet knife can then be used to cleanly sever the rope in the melted area. Next, melt the exposed fibers at the end over the flame and press the cut section smooth by rubbing it over the still warm plastic (gloves).

The process becomes more complicated if the rope or cord is made up of different materials. There are cords with a Dyneema® core and a polyamide sheath, an aramid core and a sheath containing polyester, a polyamide core and a polyester sheath, or a sheath made of both polyamide and aramid, and all other conceivable combinations. The problem in such cases is that the materials don’t bond together when melted or, as in the case of aramid, burn rather than melt.

In the case of the combined use of polyamide and polyester, the easiest solution is to sever the rope with a hot cutting device and then use the device’s blade to make a transversal cut in the rope end before rotating the rope by 90° and making a further such cut. This significantly enlarges the melted area and creates a positive fit between the fibers once they harden instead of a chemical bond. The surface of the melted areas can then be smoothed with the blade again.

In the case of cords made with Dyneema® (UHMWPE) or aramid, heat is often not the ideal tool. Instead, such combinations of materials should ideally be bound with adhesive. This occurs as follows: first, adhesive tape is wrapped around the cord at the intended cut point. A sharp knife, ideally a carpet knife, is now used to sever the cord in the middle of the tape. Low viscosity, i.e. very runny, glue, ideally cyanoacrylate-based (super glue), is now applied to the exposed cut. Caution: a suitable surface and gloves as well as sufficient ventilation are required! Due to the capillary effect, the glue is quickly absorbed into the fabric and binds the fibers. The tape can then (but does not have to) be removed. If you like, you can also apply a little glue to the last few centimeters before the end of the rope and allow it to absorb. This additionally stiffens and glues the end.

As with all PPE products and servicing measures, don’t forget to relabel the rope and document the work!