Case XX Rigging knife - Need "marlin spike"

[LemmyCaution]

For anyone interested-

A shackle rigging connection does not gain strength by being wrench tightened. Quite the opposite- wrench tightening a shackle puts a load on the bow that reduces the strength of the connection. One mouses a shackle because ideally the clevis pin is installed finger tight. There needs to be some means of preventing the pin from backing out under vibratory or shifting load.

Frequently, when a shackle has been loaded at or near its capacity, the pin will become stuck. Or, in salt air or exposed to spray, galvanic corrosion will gall the threads of the clevis pin. In these cases, the shackle cracker, or breaker, is used to loosen the stuck pin. The shackle cracker should not be used to tighten a pin, unless absolutely necessary (because one has nothing to use for mousing), and the load is assured of being static and constant (because no matter how tight one gets the pin, it will back out under a vibratory or rotational load).

 

[zorro45]

I prefer to use a hollow fid made out of a piece of copper pipe but the one you are looking for is a lot prettier and corrosion resistant.

 

[LemmyCaution]

I prefer to use a hollow fid made out of a piece of copper pipe but the one you are looking for is a lot prettier and corrosion resistant.

A fid is, by definition, made of wood or bone. If it's metal, it's a marling spike.

 

[Willie Sutton]

^^ Not absolutely so.... Fids can be made from anything and are often hollow...

Just an example of a commercial hollow fid for braided rope splicing:

http://www.amazon.com/WELLINGTON-CORDAGE-S6034-Splicing-3-Pack/dp/B000R2POFW


I had a few other corrective comments prepared for your shackle note, but didn't post them as they are not germane to the discussion in general.


Willie

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[rcmodel]

I made the mistake of buying that exact same set when my old poly rope fid went MIA.

The smallest one is too small for 1/4" rope.
The middle one is too big for 1/4" or 5/16" rope.

And the biggest one is too big for any rope smaller then 1/2" rope.

Or any size poly rope we use for Macramé in Kansas!

They are not even threaded inside to keep the loose end from slipping out.

rc

 

[LemmyCaution]

I had a few other corrective comments prepared for your shackle note, but didn't post them as they are not germane to the discussion in general.

PM me. I'm interested to hear your opinion.

 

[Willie Sutton]

^^ It'll be later, I'm travelling and don't have lots of time. But, In short, it depends on the design of the shackle, the size, and the application.

Bottom line is that Torque on the pin does not increase or decrease working strength, it just prevents unwanted disassembly *in some shackle designs*. There are hundreds of shackle designs, but the baseline "common one" has a flange on the dead-side of the pin and threads cut to a length on the threaded side that prevent "bowing" the shackle itself more than a very precise tensioning amount when they are threaded home. The bow-tension is the anti-unscrewing mechanism *on some but not all shackle designs*.

On order to put some OP's content in this, the spikes and slots on knives and tools in the size class we are discussing are designed to fit small stainless steel shackles on a sailboat. Think about a 1 inch long SS shackle made from stamped SS and you'll be scaled correctly. These are MOST DEFINATELY engineered to be pre-tensioned by a tool to bottom out the threads on the pin into the receiving threads on the shackle, tensioning the shackle very slightly, in order to not need mousing in use.

These are not the shackles sized where you need a crawler-crane to pick up the pin from the deck of the ship to handle (I've worked with those too as a commercial diver). Nor are they the 4" shackes used for basic utility on the farm. It's all a matter of what's right for the *individual* application.


Willie

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[LemmyCaution]

Willie-

Yes, you are correct that some shackles are designed such that wrench tightening them will stop the pin at a safe tension. I disagree that this is the baseline, or most common variety. In my experience, such shackles are a rarity outside of marine applications, where materials and finishes tend to be of a higher quality. In my trade, where working loads are specified and calculated very closely, and adhered to religiously, the shackles are not of the design you detail above. And there is great variance in the quality of the shackles from manufacturer to manufacturer, and on lower quality shackles from shackle to shackle within a given lot. I've seen Chinese shackles that have pin threads that will only fit the bow they came with- essentially hand cut. I've seen meat-headed iron workers strip the threads with a wrench. I've seen novice riggers install a shackle with the pin on a running line and spin the pin out. I've seen shackles permanently deformed by wrench tightening to a degree that, once removed, the pin cannot be reinstalled.

Further, unlike in a marine environment, where a shackle might be removed and reinstalled several times a day, in my trade shackles are frequently installed and left in place for the service life of the equipment, which can be 60 years or more. As such, it would be unwise to rely solely on spring tension to keep the pin in place.

My company buys 1/4" SPAS in 30gal drums. I've seen and handled a whole lot of shackles from 1/4" to ~3" over the last 30 years. Generally 200-400 every week.

So let me amend my statement to read "Wrench tightening a screw pin shackle, in all but very circumscribed applications, is risky and should be considered poor practice, unless one knows exactly what one is doing and has taken careful account of all variables that will affect the shackle throughout its service life. Mousing is a better practice, though impractical in certain applications."

 

[ApacheCoTodd]

This whole shackle drift is fascinating...

and completely relevant to me. I figure replacing the original style with a shackle wrench spike is a goer now given the above input.

As to use, I can't imagine caring to tighten with it but coping with post-use tensions whether load induced or various cruds causing resistance makes a slotted spike more practical to me than a round eyelet as originally provided.

Thanks for the drift fellas. The Myerchin is ordered.

 

[LemmyCaution]

Excellent choice, sir!

 

[Willie Sutton]

"Further, unlike in a marine environment, where a shackle might be removed and reinstalled several times a day, in my trade shackles are"

<snip>

Lemmie:Here's the problem. We're not talking about what's used in your trade. You're an expert in an allied field, but not all similar things transfer well to other applications.

Here, we're talking *specifically* about the marine environment and a specific tool used for a specific application within that environment. The tool is used on small scale shackles. I think your "1/4 inch shackle" is a 1/4 inch pin diameter one which is not at all what we are discussing. We are talking shackles that range from about 1/2 to maybe 1 1/2 inches overall in height with bow widths of between 3/8 and maybe 3/4 inch. Think SMALL. Think sailors, and not iron workers.

Todd, if you hand-tighten a marine sailboat-application sized shackle by hand using your fingers, it WILL come undone under normal use. The shackles MUST be snugged to prevent the pin working out. This is based on about 45 years of experience aboard boats (I live aboard one 6 months a year), as well as many years working as a commercial diver in the offshore oil fields rigging loads running towards the 1000 ton range (yes, we rigged to lift salvage weighing up to one thousand tons...) using shackles and wire. I know a few things about shackles both small and large. Your spike is all about the small ones. Stick the point into the hole on the end of the pin if it has one and give a little extra torque to it, or drop the slot over the flats on the end of the pin if it doesn't have a hole and do the same thing. Not too much... just a bit.


Willie

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[LemmyCaution]

Wilie-

Perhaps you'll be surprised to learn that rigging knives have applications outside of marine rigging. I carry one every day. And I work every day with exactly the same size shackles we are discussing.

I've qualified my opinion to exclude your specialty. But to assert that my specialty isn't relevant to discussion of rigging knives and marling spikes is reaching.

Further, the class of shackles we are discussing are, in fact, designated by their pin size, as it is this nominal diameter (the pin is generally slightly larger than the nominal diameter) that designates the thickness of the stock, which correlates to the load rating of the shackle. Designating a shackle by its overall dimensions is less helpful, as is clearly indicated by the size difference between, for example, a 1/4" chain shackle and a 1/4" headboard shackle, both of which should have approximately the same load rating, but the headboard shackle will be around twice as long. And when we're talking about rigging tackle, the load rating is what it's all about.

 

[ApacheCoTodd]

Regardless of professional particulars...

this is a tool I never knew I needed.

I've used various shackles in the family's trucking business, in a career in the Army and as a civilian in the woods, vehicle recovery and weird make-do rigging. Generally I would finger tighten and snug with the inside of a pocket knife and use the same knife if things grew too tight. Sometimes "safety" it with a strand of 550 cord gut or wire.

Having a dedicated rope knife with its own rope wrench and a shackle wrench seems like a combo I should have come across sooner.

Such is the ignorance of a 'lubber I guess.

Funnier now that I look back and thought the slot in the sheath was for a steel.

 

[rcmodel]

I don't know about you?

But I am almost Shackeled out!

I didn't ever need one in Kansas either.
Except the trailer hitch ones you stick a pin in and hook a log chain too when you get your Pick'm-up or tractor stuck in what mud there is every few years!
But we called them Clevises.

I did use a couple of shackles on the Anchor ropes on my old bass boat years ago.

But I can't remember if I tightened them with a screw-driver, crescent wrench, or with pliers?

I am sure I didn't use the Marlin Spike on my old British Navy folding knife though.
I never could get it open without breaking two fingernails off.
(And all along, I thought it was only used for splicing hemp rope???)

I know for sure I didn't Mouse, Rat? or Gerbil? them though.

And they were still on the anchors when I sold the boat.
So I must have over-tightened them?

Pity the fool that bought that boat if I over-torqued them with my Leatherman pliers the last time I replaced the anchor ropes!

rc

 

[ApacheCoTodd]

I've used spikes, nails and other rope wrenches quite a lot but I'm one of those fellas that sees knots as challenges and specifically like using the most secure and removable knot that I can.

Cracks my wife up at how long I'll work at a knot before giving up. After that, if there's a tool I'm gonna have anyway - and it keeps me from splitting my folder sides anymore, I'm in.

The Ford-Chevy or Colt-S&W level of debate surrounding shackles here has provided me with info I would never have though to come a cross on this type of forum.

All 'cause of a found thing at an estate sale... Go figure.