Hitch mounted shackle Q's

I understand yalls concerns....but come on people. It's a tow hitch. I have jerked on shit so hard my back tires came off the ground. Strapped the receiver shackle to a tree and hooked 10k winch with double snatch blocks to a stuck spreader truck with over 10k of lime in it. Pulled it out no problem. Your truck doesn't have enough power, nor does it weigh enough to ever hurt the receiver hitch or a 3/4 inch shackle. Also as a helicopter pilot, when I see someone do the whole "1/2 turn back" thing on a rigging shackle, I land and escort them to the nearest vehicle and tell them to stay in it till I am done lifting. It is stupid and it makes no sense. Yall do realise that shackles are load tested, and fail tested to determine the safe WWL, and they are tested with the screw pin finger tight right? Oh your gonna jerk on this shackle that is attached to straps that could contract and accelerate it to deadly speeds..ok well you should help it come undone by unscrewing it some first. Terrible advice.

 

That was harsh, sorry I broke my knee and it really hurts

 

I just use the pin for my trailer hitch. Shove the strap in and insert the pin and clip.

The frame will snap in half before the pin bends or breaks.

 

A straight pull is fine for that, but be very very careful. The smallest angle, vertical or horizontal, and the edges of the receiver tube will cut the strap just like a knife will.

 

Good point.

I haven't yet had to use my method, hoping I don't have to before I get a real bumper (front and rear).

 

Wear on the strap is the concern. Lots of people do this and it's strong enough. I prefer to use a bow shackle if I can.

 

If I understand what you're ranting against is the advise you sometimes hear about leaving the pin on the shackle a little loose as insurance against it locking in place.

From one manufacturer's website: http://news.thecrosbygroup.com/news/shackle-to-shackle-by-crosby

"The screw pin threads shall be fully engaged and tight and the shoulder should be in contact with the shackle body."

 

Just be careful on how much directional / lateral force you put on your hitch receivers. They're not built to take a strong sideways pull.

 

Thread revival!

This is great info for a newb. Where does one find some of the strong hitch pins referred to in this thread? Most sites just sell the receiver and/or shackle.

Thanks!

 

https://www.amazon.com/gp/aw/d/B01M...+hitch+pin&dpPl=1&dpID=31HAz-FjDQL&ref=plSrch

 

I use a 5/8" grade 8 bolt personally.

 

That's bad. Not only will DOT give you a ticket for that if they see it, bolts are tested for tensile strength (pull) and not shear strength. A grade 8 bolts as been hardened so it will take more pull to break it, but it does not stretch or bend, it just shatters. You don't want a hitch pin that shatters, you want one that will bend and bend and bend and hold that hitch in with its very last breath and then break. If grade 8 bolts worked as hitch pins, why would hitch manufacturers go through the trouble of making a pin. They would just slap a grade 8 bolt in there.

 

But if you ever do break a grade 8 bolt using a tacoma then you are most definitely getting some shit done

 

I dunno about DOT, I don't tow anything. This thread is about a hitch mounted shackle adapter.

The question of grade 8 has been around forever. It is true that as you heat treat a fastener to a higher tensile strength it loses ductility and becomes more brittle. That means the region between yield and ultimate shrinks. It still has a point where it will deform.

The SAE charts for fasteners lists for bolts under 3/4" grade 5 proof is 85,000 psi and tensile is 120,000 psi. For grade 8 proof is 120,000 psi and tensile is 150,000. This means that even though the margin between proof and ultimate is smaller the grade 5 will have broken before you reach the proof point of a grade 8.



But in this case we're worried about shear, which is generally assumed to be 60% of the tensile.

For my 5/8" bolt.



A = (.3125)^2 * pi = 0.307 sq-in

Proof is therefore 0.307 sq-in * 120,000 lbf/sq-in = 36,840 lbf

Taking the 60% assumption for shear = 0.307 sq-in * 150,000 psi * 0.6 = 27,630 lbs.

Then for a hitch the pin is actually in double shear, so it's twice that at 55,260 lbf. In a recovery using my shackle adapter the grade 8 bolt is one of the last things I'm really worried about. Even if it's an impulse, which a shock load would be the concern on a fastener that more brittle, an 8,000 kg snatch strap is going break before the bolt.

The reasons I use it are (1) I know a grade 8 bolt from a known source is actually grade 8. I couldn't tell you for sure what is true of a random hitch pin. The pins I have for my tractor 3-point are grade 5, so I would assume that's typically the case and I would trust that to be true from a reliable source.

Second, using a bolt allows me to use a thick washer on each side of the hitch receiver and a lock washer and nut. So I feel the hitch is better supported and the pin/bolt isn't rattling around or sitting there rolling in the hitch.

If I was towing I wouldn't necessarily come to the same conclusion, but that's my logic for using a bolt with my adapter anyway.

Also think about this, the shackles and hooks we use sometimes get heat treated to grade 8. The Gunnebo hook I have on my winch is a G-8-10 series, which is heat treated to use with grade 100 chain. The material characteristics can't be taken out of context individually, being brittle is only important if your load is large enough for it to matter.

 

That's all true, and I agree 100 %, but what you are no remembering is the hitch does not fit tight and will rattle and move, it's not solid like it should be when using a hardened bolt. If you can get it tight enough that it snugs the bar up, then hell yeah use one. But that won't be possible, cause if you side load threads they become a sheer point where they connect to shank. As far as shackles go, if you get them from the fastener section they are like $8 and are only rated for 1700 lbs. The same size shackle for my sling equipment will hold 4.5 tons and costs about $14. Thats because it's forged metal, like a hitch pin, and it's stronger. When I lift bags of fire retardant mix for the forest service, they do inspect at the beginning of the season to see what rigging you have. I had a 4 wheeler trailer on my truck and a drunk guy hit me head on once. He narrowly missed my truck and hit the trailer square it the corner. The cops got there and we started looking and it broke the hitch ball, but not before it pulled the hitch bar into a "v" shape. The hitch pin was clearly deformed and bent, but it didn't break. I am pretty sure a bolt would have just broke.

 

Thanks all. I appreciate the info

 

Most bolts are hardened, the grading is telling you how much. A grade 5 is hardened to lower state (Rockwell C25 to C34) than grade 8 (Rockwell C33-C39), which is a byproduct of the treating they needed to get to reach their tensile strengths. A grade 5 is therefore more brittle than a grade 2. The question is a matter of degree. You should never use grade 2 or ungraded bolts on your truck, BTW. The flip side of the brittleness is being harder a grade 8 is more resistant to physical damage, e.g. it's a "tougher" bolt.

That the joint isn't a tight fit doesn't matter, the load is the load. It changes the nature of the load. In this case the bolt or pin would be completely in bearing shear instead of clamping tension and friction shear. The object just needs to be able to deal with the load it's presented. The hitch pin and a bolt are undergoing the same loading. If the joint was tight and there was clamping the joint itself may hold an even higher load than the bolt/pin alone. But it isn't so it's just the shear of the bolt alone.

One thing you should try never to do is a single shear bolt that puts a bending moment on it. That's where you get into trouble with fasteners, putting both compression and tension on opposing sides of it.

Forging is how the steel shape was formed (as opposed to cast, NEVER use a cast shackle) from the original billet, ingot or bloom delivered by the foundry. A bolt can also be forged or rolled then maybe machined (depends). Heat treating is a separate process, could be done in various places in the production of the bolt, shackle or whatever else. The raw material was probably heat treated to some extent to meet the ASTM material spec the next factory in line requested.

All shackles are heat treated, quenched and tempered, to give them whatever properties they need. They need to be tough but ductile but also hardened and stress relieved. There's a lot that goes into making this stuff.

FWIW, the shackles we typically use in 4WD are grade A carbon steel hardened to grade 6 and not grade B alloy steel you may in aviation. You can tell instantly because a grade A 3/4" carbon shackle is rated 4.75 tons while the same size grade B 3/4" shackle would be rated for 7 tons.

I also only buy known shackles from trusted sources, Crosby, Gunnebo, Van Beest, Columbus-McKinnon, etc. I don't personally even trust major name brand Warn, etc. Only primary manufacturers from sources known not to sell counterfeit. You can't get good shackles from Home Depot or 4 Wheel Parts or from eBay (usually). The place you buy them should be able to furnish certification or traceability documentation and if they can't they probably aren't approved to distribute or sell the brand.

Your hitch pin did exactly what a grade 5 bolt would have done. That's all a hitch pin is, an unthreaded, loose fitting length of rod. If you cut threads in then it becomes a threaded rod. Put a 6-sided cap on it then it's a bolt. There's nothing magical about any of this. You start with iron, smelt and alloy it into steel, form it into a shape and treat it to whatever it needs to be.

So a grade 5 hitch pin that's 5/8" in diameter is going to do the exact same thing as the shank (unthread part) of a 5/8" grade 5 bolt would in the same application. There is a small reduction in strength of a bolt due to being threaded, which is reducing the diameter to the minor diameter. That's something I did not calculate for before but should be mentioned.

 

All I can think is this:

 

Me too. The shoulder sticks just past the receiver tube so it gets a washer and nut.

 

Your previous quote was not harsh at all. Someone was asking a good question and someone else gave improper info. in response. A shackle with a threaded pin is indeed suppose to be tight. Do not back off any amount. Yes it eases removal after loading but it is designed and the rating is with the pin tightened. Check with Crosby if you want, I actually advise you to do so. All off roaders or anybody pulling, lifting or performing recovery should take proper rigging classes. Not only will or can learn to protect yourself but how to do it efficiently.