The four advantages to using Grade 8 bolt vs. a hitch pin - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 10 (permalink) Old 03-16-2007, 03:14 AM Thread Starter
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The four advantages to using Grade 8 bolt vs. a hitch pin

The four advantages to using Grade 8 bolt vs. a hitch pin:

- Grade 8 is stronger than the grade whatever standard hitch pin. Gr8 is 130-150KSI, the only numbers I see on a HP is 36ksi from a page in McMasters. Read Table 1 and the "What Grade" discussion bottom of page 8 here: http://www.pirate4x4.com/tech/billav...lts/index.html

Grade whatever will bend and break before Gr8 even starts to bend, much less break. Shear strength is directly related to tensile strength as discussed in the paper above (shear = .6 tensile).

- A friction shear joint is created due to torquing the Gr8 bolt down to at least 150 ft-lbs, while a standard hitch pin or locking pin provide zero friction shear strength. Read more about friction shear joints on the bottom of page 4, same paper as above.

- Torquing the bolt to +150 ft-lbs. eliminates all "slop". Hitch bar is like a rock.

- Increased security over a standard hitch pin. Unless thieves come with 15/16" wrenches or maybe a couple of crescent wrenches, the bolt isn't coming off vs. pulling the pin on a standard hitch pin. However, it has less security than a locking pin, since it does only take wrenches to take the bolt and nut off and then the hitch bar.

I do size my Gr8 so that shear forces are on the main bolt diameter and not on the threads, so I have that covered also.

Good luck.

Al
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post #2 of 10 (permalink) Old 03-26-2007, 02:42 AM
 
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also, I had a hitch vibrate and it rubbed through the pin and I lost a horse trailer, almost over the side of a cliff
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post #3 of 10 (permalink) Old 04-10-2007, 07:30 PM
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I have thought about doing this before, and drilling for a padlock in the grade 8 bolt (tough drilling job!).

When torquing to 150 ft-lbs, do you end up permanently deforming the hitch at all? I was worried about such deformation when using a thin-walled ball mount.

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post #4 of 10 (permalink) Old 04-16-2007, 05:45 PM Thread Starter
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Michael,

My ball mount is a 2" solid steel square bar. I have no worries about deforming it or the hitch.

If it was hollow, like some are, I'd probably not torque it down as much.

Part of the reason for the torque is to eliminate the slop, partly for strength (friction) and partly to ensure the nut stays tight and you don't lose the ballmount. A lower torque would still work on all three areas, with less fear of permenantly distoring the ball mount.

Good luck.

Al
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post #5 of 10 (permalink) Old 05-22-2007, 02:23 PM
 
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A Nylock locking nut would work well also for less than desired torque.
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post #6 of 10 (permalink) Old 07-01-2007, 09:35 PM
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I don't really care for nylocs steel locks work better for me,but if it works then good deal
Later
Travis
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post #7 of 10 (permalink) Old 07-18-2007, 08:04 PM
 
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nyloc nust aren't gr8.If you are going to put the hitch in the receiver and leave it, I would use a steel lock nut. I don't leave my hitches in because they tend to become one, if you know what I mean.
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post #8 of 10 (permalink) Old 01-16-2008, 12:23 PM Thread Starter
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Quote:
Originally Posted by paul1987
nyloc nust aren't gr8.If you are going to put the hitch in the receiver and leave it, I would use a steel lock nut. I don't leave my hitches in because they tend to become one, if you know what I mean.
And that is definitely a disadvantage to those living in places where they salt the roads or people who live near salt water. Liberal use of grease on the ball mount would reduce or maybe eliminate this problem, but then that also eliminates the friction part of the equation also. Such is life.

Al
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post #9 of 10 (permalink) Old 03-25-2010, 02:56 AM
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I also am a big fan of using a grade eight bolt, my receiver is 2.5 inch, but same 5/8 bolt I use a flange bolt with a hard washer, and a flange nut, with a hard washer. I worked in a shop so getting bolts was not a problem. With the price of the 2.5 inch hitches, I do not leave it in, it really hurts when you walk into it. Especially if I have on the goose neck, and you are not paying attention.

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post #10 of 10 (permalink) Old 03-25-2010, 01:50 PM
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Just puttin some prior info on the table.

https://thedieselgarage.com/forums/sh...ght=grade+bolt
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