For simplicity – 316 Stainless Steel fittings and 3.2mm G316 1×19 Stainless Steel Wire Rope are assumed in this discussion. And a similar discussion applies to 2.4mm and 4.0mm wire and fittings as well.
Virtually all of the hydraulic swaging/crimping tools that are sold to the masses for work with wire rope – originate from electricians’ tools. The critical difference is the dies that are used in the tools. General practice is to simply repurpose existing packaged tools. The standard “package” (usually called an HP-70 or a YCP-70 … and if there is an appended “C” that means it incorporates a factory set pressure relief valve) of a 5T (which is actually an extremely obscure measurement because the tools vary from about 4T to 6T – and are advertised at all sorts of ‘tonnage’) normally has die set that are 4,6,10,16,25,35,50, and 70. We have a different set because the #8 is non-standard.
Please also note that the reported tonnage of the tool – is across the surface of the head of the ram. And you do NOT use the surface area (contact surface) of the ram itself to press anything. You use dies that have a vastly smaller contact surface – which ENORMOUSLY elevates the effective crimping pressure. This contact surface area is incredibly important that lets a relatively weak 5T tool approximate what a proper 100T press can achieve (which MUCH bigger dies and a bigger contact surface).
Now all of the commonly available dies in a standard “package” that have a number on them (e.g. 4,6,8,10, etc) which is not relevant in the least to wire rope sizing or stainless steel fitting sizing (either metric or imperial) These dies sets are labelled and sized according to AWG standards and the number reflects the cable cross sectional size used with the relevant electrical fittings.
We term these GH-X where GH stands for Generic Hex and X is the AWG (American Wire Gauge) number. These are quite reasonable and have a smaller contact surface. This GH terminology separates these sorts of dies from our specialized HH-x where HH stands for Hardened Hex and X is the diameter of the wire rope that suits the fitting to which the dies are applied. HH dies have a wider contact surface and are manufactured with a much higher level of precision
The size GH-6 die set is recommended by many purveyors of these tools because their tools do not have a size GH-8. (We have added the GH-8 set to our tool as it is a better approximation of the “correct” size dies). A GH-6 sort of works – but it ‘pancakes’ the swaging tube. A GH-8 achieves (measurable) uniform compression.
And about the dies “closing”… if you think about it – the dies should NOT close. Because if they close, then they are no longer compressing the fitting, they are just squishing each other. Interesting side note is that when you are swaging big stuff with a very big tool – one trick is to put a piece of paper between the dies. You know you are ‘done’, when you are exactly at the pressure that prevents you from sliding the paper out from between the dies.
And back to a ‘correct’ set of dies for swaging 3.2mm stainless steel fittings… Well – you really have to first define the criteria of ‘correct’. And that correctness is akin to a safety factor that is used in rigging to determine SWL (a misnomer) from MBS. It is very application specific. For example – putting up balustrade wires is one thing – but rigging a yacht that is used in the open ocean is vastly different.
However, from a maritime survey perspective, a stainless steel fitting for 3.2mm Wire Rope has a nominal OD (before pressing) of 6.35mm (+/-0.010) and any die set that when applied to the entire length of the swaging tube (a nominal 38mm) achieves a reduction in OD to 5.44mm-5.56mm is correct (and insurable).
So if you read between the lines, there is no such thing as a “correct” set of dies, or a “correct” tonnage of tool – it is actually the clever application of force by a skilled craftsman – by whatever means available – to achieve a result that meets their criteria of an acceptable result.
Happy Squishing…