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Bolt Carrier for 8” Grade 8s?

So what is the shear strength of a 3/8" grade 8 bolt across the thread section? To me, that has to be part of the discussion when comparing how 6" will be used versus 8".
I've always maintained that the entire threaded section must be fully inserted into solid wood because it's the integrity and strength of solid wood (not bark) that supports the bolt's shear strength. The weakest link would be a portion of the threads that might me not inserted into solid wood.
So getting back to the drill part of the equation when boring a thick barked tree...Will the bit drill deep enough to penetrate the thick bark and still bore deep enough so that the bolt's threads are completely encase within solid wood? I think the point of using an 8" bolt on such a tree is the user's tolerance of how much bolt is available for hand and foot support. If the bark is ~2" thick, then it essentially reduces the usable portion of the bolt by 2" when compared to a tree with thin bark.
We can't discount the leverage factor of the 8" bolt. An 8" bolt will tend to bend easier than a 6" but, if there is no thread exposure (the unsupported thread section) is not a factor then will the leverage bend the 8"? I think that's an answer that each individual will have to decide for themselves.
And regardless of bolt length...Keeping the bore hole nearly level will reduce leverage.
 
Allegheny Tom said:
So what is the shear strength of a 3/8" grade 8 bolt across the thread section? To me, that has to be part of the discussion when comparing how 6" will be used versus 8".
I've always maintained that the entire threaded section must be fully inserted into solid wood because it's the integrity and strength of solid wood (not bark) that supports the bolt's shear strength. The weakest link would be a portion of the threads that might me not inserted into solid wood.
So getting back to the drill part of the equation when boring a thick barked tree...Will the bit drill deep enough to penetrate the thick bark and still bore deep enough so that the bolt's threads are completely encase within solid wood? I think the point of using an 8" bolt on such a tree is the user's tolerance of how much bolt is available for hand and foot support. If the bark is ~2" thick, then it essentially reduces the usable portion of the bolt by 2" when compared to a tree with thin bark.
We can't discount the leverage factor of the 8" bolt. An 8" bolt will tend to bend easier than a 6" but, if there is no thread exposure (the unsupported thread section) is not a factor then will the leverage bend the 8"? I think that's an answer that each individual will have to decide for themselves.
And regardless of bolt length...Keeping the bore hole nearly level will reduce leverage.
Click to expand...

Here are some specifications I found. 150,000 pounds per square inch.

Grade 8 Bolts - Coarse and Fine Thread - Grade 8 Nut and Bolt Assortments (nutsandbolts.com)
 
My guess is that it is as strong as a solid shank bolt at of the same dimeter as the bottom pitch of the threads. For instance. The body of the bolt is 3/8 (.375). For a 3/8-24 coarse thread, a 21/64 drill is recommended for tapping a corresponding hole. Some material will be cut out in tapping so I would say it would be a good ballpark number to say you have 21/64 of solid material between those threads on a 3/8 bolt. So about .328. You could even round it down to .300 and if the breaking or bending strength of that number is acceptable then it should be ok.
 

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A simple solution if in doubt about the threads would be to buy a 10 inch bolt with short threads on the end and use a cut off wheel to remove 2 inches so now you have an 8 inch bolt with no threads. In the video by Warren Womack I linked earlier, he talks about cutting some part of the threads off the 6 inch bolt.

If you were only doing 10 to 15 of them that would not be too bad. They last forever as far as I can tell. I've lost a few in the woods but never bent a grade 8.

I just wish I could use these things more often.
 
cibor said:
Do the threads serve a purpose?
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In a way, yes. If you push the bolt into the hole or pull it straight out it will come out easily. If you put weight down on the bolt like you are climbing and try to remove it the threads bite into the top of the hole at the back and make the bolt tight in the tree. It is a subtle thing but makes a difference. John Eberhart talks about this in one of the recent videos.
 
NMSbowhunter said:
In a way, yes. If you push the bolt into the hole or pull it straight out it will come out easily. If you put weight down on the bolt like you are climbing and try to remove it the threads bite into the top of the hole at the back and make the bolt tight in the tree. It is a subtle thing but makes a difference. John Eberhart talks about this in one of the recent videos.
Click to expand...
I thought so, just saw you mention removing cutting off threads so I wanted to understand.
 
I would use threads for that reason but no I would make sure you and enough bolt in the meat of the tree to support your weight. This might mean buying a 3/8 Irwin speed bore bit and putting a stop collar on it so you can drill a 4 inch hole. I tried the 3/8 Irwin and the bolts slide right in and out, no problem.
 
This is all in an attempt to get over the issue of deep barked trees and the need for longer bolts. Normal trees with average bark are fine using the 6 inch grade 8 bolts and the Treehopper or EZcut drills. People have been using them for a long time.
 
NMSbowhunter said:
My guess is that it is as strong as a solid shank bolt at of the same dimeter as the bottom pitch of the threads. For instance. The body of the bolt is 3/8 (.375). For a 3/8-24 coarse thread, a 21/64 drill is recommended for tapping a corresponding hole. Some material will be cut out in tapping so I would say it would be a good ballpark number to say you have 21/64 of solid material between those threads on a 3/8 bolt. So about .328. You could even round it down to .300 and if the breaking or bending strength of that number is acceptable then it should be ok.
Click to expand...
I just spoke with my neighbor who is a journeyman machinist. The guy knows his stuff. He says the weakest part of the bolt is the spot where the threads meet the shank. If that precise spot isn't fully inserted within solid wood of the tree, that would be the point of failure.
So getting back to the post that asks about using 8" bolts, the important thing to remember is that the entire threaded section should be fully into the wood (not just somewhere in the lades of bark.
 
cibor said:
Do the threads serve a purpose?
Click to expand...
The threads also assist in removing bolts that are in a tight hole, either short-term tightness or also bolts that have been in a tree for a growing season. With tight bolts, they can be unscrewed. So the threads help retain the bolts and the also assist in removal of tight bolts.
And I've said this until I'm blue in the face...the best tool for bolt removal is a pair of mini vice grips.
 
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