316 SS and bolt cutters

Ian_Edwards

Ian_Edwards

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I've just bought some bolt cutters, as the almost mandatory safety device, although personally I think a good hack saw with good quality blades or pulling the pins on the chain plates are good options. The bolt cutters say they are good to HRC35, which I take to mean Rockwell C 35. I’ve looked this up on the web and it converts to an ultimate tensile strength (UTS) of 1103MPa. 316 SS has a UTS of 579MPa, so all looks OK, a safety factor of almost x2.
But that’s an annealed value, if the 316 SS is cold worked, like the way the wire is swaged into fitting, it look like the UTS could go as high as 1241MPa, which is above the rating for the cutters.
In addition the cutters work in shear, so is UTS the correct value to be looking at?
Since I’m no expert ... just trying to understand if the bolt cutter will really work when I really need them to. Am I on the right track??? Where do I aim the cutter? Presumably not the rolled swage, but at the wire or at the treaded part of the turn buckle?
Any expert help and guidance out there?
Cheers
Ian
 
As someone who is "not an expert" you are doing pretty well Ian.
You are correct that SS rigging wire is difficult to cut and the values you have given are pretty well on the button. In theory you should be looking at relative hardness of the SS to the blades, which should be OK from what you have said and shear strength which is quite high for SS. In practice the bolt cutters most people have would not stand much punishment cutting a lot of SS rigging wire but are adequate for emergency use. There is no way a hacksaw would work in an emergency holding a floppy rigging wire in one hand and cutting with the other. Just try it on a spare piece of wire and you will soon find out! There are explosive bolt cutters and other expensive kit you can buy but if the jaws are hard enough to cut a bolt you are pretty well OK on rigging wire with a good quality bolt cutter.
 
Cast 316 stainless is quite soft and will easily be cut with croppers. 316 doesn't work harden as much as some other grades, the highest tensile strength I can find being cold rolled 301S21, which reached 1235 N/mm2. I don't have a figure for cold rolled 316 but the text in my reference implies that it's a good deal lower.

Hard drawn wire, such as your shrouds are made from, are almost certainly nowhere near the maximum that can be obtained. However, the values we are discussing are tensile, whereas typically the shear strength of metals is around a third of these values.

I think the Rockwell C figure may be more concerned with the ability of the steel to keep its edge, rather than strength. Most cutting tools have a hardened edge coupled with a tough interior. The length of the lever is of more importance. i.e. can you physically create enough strength to cut through the wire? I can advise that my 18" bolt croppers won't cut 7 mm wire, whereas my 36" ones go through it with ease.
 
Thanks for the advice, I bought 30" cutter and the largest wire size on the boat is 10mm, so it sounds like they work in an emergency.
http://akcoatings.com/pdf/markets_products/stainless/austenitic/316_316L_Data_Bulletin.pdf
seems to give the increase in hardness for cold working, if I'm reading it correctly. But if the shear strength is ~1/3rd the tensile it shouldn't be a problem. I'll oil them well and seal them in plastic .... so they'll be ready should I ever need them.
Cheers
Ian
 
When cutting wire you are not cutting a solid 7mm strand you will be sequentially deforming and spreading the strands as the jaws close. However like all things you probably wont have to find out and if you do have to you may find that the immement danger and stress of the situation will give you the strength to knaw through the shrouds with your teeth.... well maybe not quite....
 
I too have a large bolt cropper, although mine is of dubious repute.
I also carry a hacksaw and blades.
I think I would try the cropper first, having taken the pins out of any unloaded stays.
I suppose the bodies of the bottlescrews would be easy to saw, being bronze, once you're through the chrome.
Or cut through the wire right next to the top of the roll swage.
It won't be flopping about much with the rig hanging on it!
Purely theoretical I hope.
Perhaps this is an argument for seizing the bottlescrews in a way you can easily undo?
I imagine the forestay would be very difficult, the bits under the harken furler are all massive.
Then there's the issue of the mast itself being keel stepped.
I think two handed we would be in trouble!
 
I would take issue with some of your statements, but note your conclusion is the same. The figures originally quoted are actually quite accurate for 316 cold drawn wire. It is not "quite soft" although your term is relative. It is for instance "harder" than mild steel.
The shear strength of steels varies somewhat but is usually in the region of .75/.85 T not .33T as you suggest. Rockwell C is simply a hardness test measured by putting a set load on a ball of given diameter and measuring the indent. The relative hardness of the tool to be used to the material being cut is all that matters and then you are simply considering the mechanical advantage of the tool considering that only human power is applied. Even then some "humans" are bigger than others! If the tool is harder than the metal to be cut sufficient power applied to the harder tool will cut the softer metal with the proviso that the compression strength or "toughness" must be high enough too or the tool will fracture before the point where the tool penetrates. To be entirely pedantic this applies only to a tool where steady uniform pressure is involved. Impact tools are different. (glass is very hard but makes a poor chisel) All stainless steels work harden to a very high degree and this has a very big impact on any attempt to drill, cut, or in any way cold work it. Drawn 316 wire already has a highly work hardened surface due to the deformation of it's surface during manufacture and while not impossible to cut with a hacksaw is very difficult and will soon take the edge off an HSS blade. However, apart from that I agree with you! /forums/images/graemlins/smile.gif
 
Fortunately, I have never lost my rig over the side, but a good friend did. It was off the north coast of Anglesey, in reasonable weather but some chop from the north. The first thing that was apparent was that the rolling of the boat was violent, having lost the damping effect of the mast.

The mast was banging heavily on the side of the boat so his first thought was to dump it as soon as possible. It was hanging on the shrouds and all bottle screws were bent, and therefore in a mix of bending and torsion on the chain plates. He said it was utterly impossible to remove any clevis pins. He walked forward to begin cutting the shrouds but the rolling was so severe that he had some difficulty in using both hands on the croppers and staying aboard. Before he had even cut one wire he dropped the croppers overboard.

Fortunately another club member was close by and he was able to pass his croppers over. This time he was able to cut all wires without too much difficulty and the rig was dropped to the bottom. His view was that he could not have done anything with a hacksaw. I would add that he is a time-served craftsman, so not unfamiliar with the use of tools.

Ever since then we have had a leash attached to our croppers, securing them to my wrist with Velcro. After that incident I had a dummy run with my 18" croppers, which was when I found out that I couldn't cut my shrouds with them. That's when I bought the 36 " ones.

Just for interest, the 'other club member' was the then owner of Conachair, now under new ownership and a regular forumite.
 
I suppose the bodies of the bottlescrews would be easy to saw, being bronze, once you're through the chrome.
___________________________________________________________________

Most bottle screws are 316 stainless.
Taking shackle pins out with the rig over the side while they are in tension is almost impossible. In any case speed is of the essence.
For those who doubt their ability to cut rigging wire in a hurry with bolt croppers, forget hacksaws..... No chance! Buy a screw actuated cutter or one actuated with a spring or explosive charge ( If she still has it you could buy one off Becky if she hasnt sold it already!)
 
I agree with all that you say this time /forums/images/graemlins/smile.gif

But just as an afterthought put a lifejacket on before you strap the bolt cutters around your wrist won't you..... Man waving bolt cutters while in water and trying to swim....not good! Better to tie them to the boat? Not the rigging of course!
/forums/images/graemlins/blush.gif OK I will shut up now! /forums/images/graemlins/smile.gif
 
[ QUOTE ]

Just for interest, the 'other club member' was the then owner of Conachair,

[/ QUOTE ]
Thanks, always nice to hear a little piece of ones' boats history. Think those cutter are still be in a locker somewhere. Incidently, in the entertainments rigging industry (and probably most businesses which involves cutting smaller dia's steel wire rope) swiss made Felcos are the only tool anyone uses. Not cheap but very good, they shear like scissors rather than compress. I have a set of c16's which are quite hard work for dyform 8mm but well up to the job. Cutting steel wire rope onboard I use an angle grinder and keep the felcos sharp for when they might be really needed.
 
have a look for some hydraulic cutters on ebay. I bought an Enerpac set for about £100 which cuts through 3/8 chain and 5/8 wire very easily, just pump the handle a few times. BTW - One of the marine companies has started selling the same unit with a marine badge for over £1k.
 
Well, not wishing to give a lecture in metallurgy, which I am well qualified to do, I didn't attempt to delve deeply into the technology of the question. In fact neither of the shear statements is correct, shear strength being recognised as being either 0.57 YS or 0.5 UTS, which comes to about the same thing. However, it is dependent upon the mode in which the shear is applied. Where the action is a cutting one, via a sharp pair of tools, the value will reduce. Where the application is blunt it may increase.

I stand by the softness statement of 316. Of course it is harder than mild steel. It is harder than plasticine as well, so what does your statement tell us? So far as a pair of bolt croppers is concerned, it is pretty soft.

I am well aware that Rockwell C is a hardness measurement too, but in what way does demonstating my superior knowledge answer the original question?

Drawn stainless steel is not highly work hardened. It is undoubtedly work hardened but deforming it to its maximum possible extent leads to the generation of surface cracking that is likely to nucleate fatigue cracks in service. It is typical to deform 316 stainless by only a few percent, increasing the yield by 2-300 MPa. Further increases are possible but additional measures need to be taken for example in spring material, and these are not normally economic in wire production.
 
Interesting to hear (see?) all the banter, but I’m still not sure I know the answer to my question, which perhaps more simply put is:
Will the Sealey AK510 (750mm ~30”) with HRC35 cutters, cut 10mm 1X19 SS 316 wire?
The answer seem to be ... probably .... yes, because although the steel is work hardened to some degree, the pressure required to shear is somewhat less than the pressure required break the wire in tension.
Most of us are keen sailors and most of us will never see the rig go over the side, but if we are unfortunate enough to have it happen, we need the right equipment and the right training/advice, so we know what to do and we’re not making it up as we go along.
Cheers
Ian
 
I have a pair of large good quality bolt cutters approx. 4ft long and last used on inch by quarter mild steel, which still required a fair amount of effort to cut. The blades are not sharp, as with a knife, but are flattened to just less than 1/16th inch.
I have never tried them on rigging wire but would be interested to hear comments re the blade and its potential to cut rigging of 10mm minimum.

I should add that the idea of trying to use them on a rolling deck is not something I would contemplate due to the sheer unwieldiness of the beast.
 
vyv,
value your actual experience of this. Was it a deck stepped mast?
I don't fancy the task with 10mm dyform and a big mast, keel stepped.
Looking through the catalogues for a cutter actually specified for 10mm, it ain't trivial, but I suppose cutting 10 wires is easier than cutting bolts all day every day.
best keep the rigging in good order I feel!
 
I'm in the process of equiping my new boat (Sadler 290) & this thread has given me the idea that I should always have with me my Dewalt 18v angle grinder. With a 1mm thick disc you'd have no trouble whatsoever going thro 10mm dia one handed !
 
Probably lighter than croppers too!
And possibly no more expensive?
I wonder what RORC would say?
You'd certainly regret leaving it at home that day.
 
Sorry about the techno-banter.

<<< Will the Sealey AK510 (750mm ~30”) with HRC35 cutters, cut 10mm 1X19 SS 316 wire?
>>>

I would say you would have to be pretty strong! I'm not sure of the exact length of mine, they are on board in Greece, but they are definitely longer than 30", more like 40" I would guess. They cut my test piece of 7 mm reasonably easily but there's a lot of difference between 7 and 10 mm (actually 3 mm!) but you know what I mean.

This page shows your croppers (I think) and it says 13 mm soft metals, 8 mm medium metals. The Rockwell C 35 is the hardness that it will cut. I can't think in Rockwell but it's equivalent to 350 Vickers, which is close to what I would expect stainless wire to be. My guide is that 400 Vickers is the limit for hacksaw cutting with difficulty, so that would seem about right.

The only way that you are going to find out is to try it. Any rigging shop will have offcuts of all sorts of wire and will almost certainly be pleased to cooperate in a scientific experiment. I shall be very glad to hear your findings.

One problem that has been highlighted in several reports is that normal bolt croppers have difficulty with wire as it slips out of the jaws. I was careful to buy a pair that had a notch in one jaw that prevents this from happening.
 
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