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Old 03-27-2013, 11:06 AM
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Default Bolting up a winch bumper, hardware questions

So I have a new bumper I bolting up to my cruiser, its a HFS CCOT winch bumper. I am wondering about what kind of bolts to use to mount it up.

I have used 3/8" grade 5 carriage bolts in the past and it never tore off, nor did I use it super hard. I like the look of the carriage head bolts on the bumper.

Can I stick with that or should I bump them up to 1/2" bolts? The CCOT bumper has holes large enough to use 1/2" bolts without drilling, but the frame horn extensions on the 40 will need to be opened up to 1/2".

There are 10 bolts all together. I am thinking grade 5 is still overkill, but I thought I would ask if I need grade 8 1/2" bolts? I gotta' buy new bolts either way so I thought I would ask. I am using grade 8 to bolt the winch to the bumper.

Thank you... discuss.
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Old 03-27-2013, 01:04 PM
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Grade 5 3/8" is fine in terms of strength, as you say--overkill.

I don't like grade 8 on bumper mounting bolts, because I like the "softer" grade 5 bolts that will deform in the event of an accident. I'd rather replace some bolts then bend a frame.

Worked like a charm when my little truck got rear ended by a big old Tahoe. Bent the bumper a bit, deformed the bolts, but that's it. The frame survived intact.

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Old 03-27-2013, 02:20 PM
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There are probably a lot of variables that need answering for someone to really answer that question on an engineering level. But I say 10 3/8" grade 5's should be plenty. Especially if they are on different planes (vertical & horizontal)
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Old 03-28-2013, 03:02 PM
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What is 3/8? What is Grade 5? Land Cruisers use 10mm x 1.50 with the proper JIS 14mm nuts in grade 8.8
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Old 03-28-2013, 03:49 PM
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Subzali, check me.

In general a grade 5 bolt will begin to deform and potentially hit its ultimate before the same size grade 8 begins to deform. The only reason in my opinion to use grade 5 is cost. If you are manufacturing trucks and were sourcing 25 million bolts, grade 8 being a few cents more each makes a difference and would be an unnecessary cost if grade 5 is sufficient. What difference does it make to us if 10 bolts cost $10 or $12?

I'd use grade 8 (or like Jeff mentions DIN class 10.9, I prefer my bolt heads to use the correct 10/12/14/17/19mm spanner progression) and the largest that fits at all critical points. The problem as I see it is you can't guarantee that all the bolts are equally loaded and so you must assume some subset of the total is doing the majority of the work. I'd go ahead and chase holes to 12mm or 1/2" with the bumper fitted to make the connections as snug as possible.

A 1/2" carbon steel grade 8 (150ksi) in single shear has a yield (assuming 60% of ultimate) of about 17,660 lbf and the same in grade 5 would be 14,130 lbf. For comparison the same in 3/8" would be 9,935 lbf and 7,948 lbf. Those numbers are per fastener, 10mm and 12mm bolts would fall roughly between those numbers, 10mm being ever so slightly higher than 3/8" and 12mm being slightly lower than 1/2". So the safe assumption is to analyze for just one bolt and then you have a whole lot of redundancy and in practice no bolt ever comes close to being stressed.
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Old 03-28-2013, 09:27 PM
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Quote:
Originally Posted by Rzeppa View Post
What is 3/8? What is Grade 5? Land Cruisers use 10mm x 1.50 with the proper JIS 14mm nuts in grade 8.8
For the benefit of those who might not know...The Grade 5 and Grade 8 specifications fall under the Society of Automotive Engineers (SAE) classification system. Not to be confused with the Society of Japanese Automotive Engineers. I'd just use barbed wire!
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Old 03-29-2013, 08:38 AM
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I wouldn't drill the frame to 1/2".
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Old 03-29-2013, 09:03 AM
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Quote:
Originally Posted by subzali View Post
I wouldn't drill the frame to 1/2".
Not arguing, just curious, but how come? Would the holes not have enough metal around them to remain strong?
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Old 03-29-2013, 09:04 AM
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Well, I don't know about the bolts, but where are the pics of this bumper?
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Old 03-29-2013, 09:14 AM
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Quote:
Originally Posted by AxleIke View Post
Not arguing, just curious, but how come? Would the holes not have enough metal around them to remain strong?
Mainly cause the frame was designed, like Jeff said, for 10mm bolts. It annoys me that even Land Cruiser specific vendors don't build their stuff with metric hardware in mind. I'm surprised CCOT doesn't provide hardware to help make the decision easier. MAF provides 3/8" hardware with their bumpers and that helps people make the decision, and most don't worry about it. 3/8" aren't that much smaller than 10mm. Shrug.

If Drew wants to "bastardize" his frame with 1/2" holes, he can certainly go for it. But then he'll become a PO ()

(note this is just my opinion, I know and understand there are other opinions out there. Because Drew's truck is stockish with mostly bolt-on accessories, it seems to make sense to not go down "that" road. If it were Wild Rice we were talking about, then do whatever the heck you want cause there ain't no going' back! (and that's a good thing ))
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