Need help with Gunnebo Slink Hook (can't fit pin inside metal bushing)

[brasskey]

Sorry for the stupid question, but I just ordered some new winching equipment and I can't figure out how to put together this hook. I bought the 3/8" SKN Gunnebo Sling Hook (Part: SKN-10-8). I don't know how to get the pin to go through the metal bushing. I can see that the bushing has some threads inside to presumably catch the pin and keep it from moving. But, I just can't fit the pin through the bushing. I assume it's not supposed to be this hard and I'm doing something wrong. Before I screw it up by beating on it with a hammer or with channel locks, I thought someone here might have one. Anyone have any suggestions? Thanks.

 

[chuck45]

Sorry for the stupid question, but I just ordered some new winching equipment and I can't figure out how to put together this hook. I bought the 3/8" SKN Gunnebo Sling Hook (Part: SKN-10-8). I don't know how to get the pin to go through the metal bushing. I can see that the bushing has some threads inside to presumably catch the pin and keep it from moving. But, I just can't fit the pin through the bushing. I assume it's not supposed to be this hard and I'm doing something wrong. Before I screw it up by beating on it with a hammer or with channel locks, I thought someone here might have one. Anyone have any suggestions? Thanks.

One end of the pin is usually a bit smaller than the other end; this is the end that goes in first. And yes, you have to pound it in with a hammer. A 16 ounce ball peen ought to be about right. The pin is retained by friction and it is meant to go in hard.

 

[DaveInDenver]

Pulling this from the thread depths since I believe this is a related question.

For future reference an uploaded image of a Gunnebo Coupling G-Link before being made up. Normally the pin is retained by the collar.





Should a fella find himself needing to replace this pin in a pinch with two otherwise intact 'G' sections would a grade 8 bolt 5/16" (this for a G-10-8 coupler) in diameter be suitable?

It would obviously lose it's traceability but it's something that could conceivably happen and finding a bolt is easier than another pin, not to mention cheaper than buying a whole new link, which run about $30. I don't know what just a replacement pin costs, that's obviously the right repair. But even if you have one with you it's not nearly as easy to install as just running a bolt through it in place and so I suspect would be the likely in-situ repair.

 

[DaveInDenver]

Doing some calculations, please make corrections. These aren't for actual use but rather a theoretical worst-case exercise.

Gunnebo rates the SKT-10-8 and G-10-8 (which are called Grade 8, which I presume dictates the pin characteristics) for 3.2 tonnes, which is 3.53 short tons (U.S.) or about 7,060 lbs. Using this load on the hook means each joint of the link should see 1/2 the load, so the bolt/pin will see 3,530 lbs in double shear.

That puts 23,385 psi on the bolt (assume diameter of 0.31 or section of 0.075 sq-in), which is well below a grade 8 minimum yield of 130,000 psi and minimum proof of 120,000 psi and is I believe a factor of safety >5.

Taking this theoretical further, assuming the hook is used on a typical winch of 9,500 lbs capacity (it's over the rating WLL already). If a single joint has to bear this it's 62,934 psi on the pin. So using 31,468 lbs on each joint is consistent with a 4 or greater factor of safety.

FWIW, I believe Gunnebo assigns a MBS of 12.9 tonnes to the 10-8 hook, which represents 28,400 lbs and a factor of safety therefore of 4. This load (2 x 14,200 lbs) will put 94,069 psi on each 0.31" diameter pin in double shear so it appears the hook itself or the casting in the link are probably the limiting factor in the failure. It's not possible for a single side of the link to bear the whole 28,400 lbs in any case.