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Discussion Starter #1
# 18 in this picture.

Cant find a single diagram with a p/n or a size for this bolt (there are 2)

Out of a disco but should be the same as defenders.

edit also thread pitch. My chart only goes up to M12, I'm thinking this is m13-20
 

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Going off memory I believe it is 1/2" x 6.5" - but I could be off by a little bit. Make sure to antiseize the **** out of the new bolts!
 

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Discussion Starter #4
Going off memory I believe it is 1/2" x 6.5" - but I could be off by a little bit. Make sure to antiseize the **** out of the new bolts!
OK - i couldn't seem to get it to thread onto a 1/2-20 nut but the threads may be jacked from hammering it out.

I'll try cleaning them up and try again.

Thanks don! Glad its standard.... makes life easier to get a new one!
 

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Discussion Starter #6
Ok. Pretty sure it's 1/2-20 and just the first few threads are jacked up

Thanks again don
 

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Could it be coarse thread, 1/2"-13?
I am sure you could do 13tpi but I believe stock is 20tpi fine thread. I would do fine thread if you had the choice.

------ Follow up post added September 13th, 2015 03:54 PM ------

OK - i couldn't seem to get it to thread onto a 1/2-20 nut but the threads may be jacked from hammering it out. I'll try cleaning them up and try again. Thanks don! Glad its standard.... makes life easier to get a new one!
Those fine threads get effed up easy - it could have been replaced by an M12/M13 at some point? I can check and see what I have for bolts in the garage if you want?
 

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Interesting article http://www.bestbolt.com/white_papers/white_paper_08.pdf Really not many reasons to use fine thread Don't worry about it Don I'll just grab something from HD or thompsons down the road.
Interesting article - agree with what they say.

I just thought that fine thread would hold its tightness better/longer in that application. Thought that is why they used fine thread for shock absorbers.

------ Follow up post added September 13th, 2015 05:29 PM ------

And Thompson will have something that will work - can't believe the stuff that guy has!
 

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In this application you want fine thread. You want the clamping pressure to provide the shear strength so that that bolts are not shear loaded. The fine thread makes it easier to ensure proper clamping force.
 

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Really not many reasons to use fine thread Don't worry about it Don I'll just grab something from HD or thompsons down the road.
Make sure you are getting grade 8. Not bolts you need breaking in an emergency stop on the highway.
 

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Discussion Starter #13
In this application you want fine thread. You want the clamping pressure to provide the shear strength so that that bolts are not shear loaded. The fine thread makes it easier to ensure proper clamping force.
Make sure you are getting grade 8. Not bolts you need breaking in an emergency stop on the highway.


Not really following you on the first one...From what i read the only advantage fine thread has is tensile strength (pulling the bolt apart literally from opposite ends). Wouldn't Shear strength depend on the material and thickness (example 1/2" grade 8 vs 3/8 grade 5) I understand if you were putting the shear load at the thread then coarse thread could be less (deeper thread cuts) but a proper sized bolt will have the shank at any shear point, not the threaded portion.

but yes, I'm going to use grade 8 yellow zinc on all hardware (that i can) on this build.

Probably overkill for many applications but rather safe than sorry. Also i found the yellow zinc plated holds up best to the elements.

McMaster Carr kills you on shipping and is often pricey. i think i may put together a list of all I need and try bolt depot out on a few orders.
 

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Are you in a hurry? I may have extras of these from doing mine - since you usually have to buy in quantities from mcmaster. I could look tomorrow evening.
 

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Discussion Starter #15
Are you in a hurry? I may have extras of these from doing mine - since you usually have to buy in quantities from mcmaster. I could look tomorrow evening.
No hurry at all. Don't even have the pcs back from coating yet

You can buy these 1 at a time since they are larger. But honestly it's nothing for me to purchase. Just wanted to make sure I had the right size since one twisted and broke taking it off and the other was banged up from removing it
 

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I got those bolts from the local Fastenal; might have had to wait a day or 2 to get them.

As someone else said, coat the entire bolt liberally with silver grease!


.
 

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If you are replacing them, the only things that matter are

grade
outer diameter
length including proper shoulder length

iic correctly the 3 are not all the same shoulder length.

You can choose whatever thread you like since you'll be buying new nuts too :)
 

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Discussion Starter #18
If you are replacing them, the only things that matter are grade outer diameter length including proper shoulder length iic correctly the 3 are not all the same shoulder length. You can choose whatever thread you like since you'll be buying new nuts too :)
3? Only 2 bolts. Typo?
 

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Not really following you on the first one...From what i read the only advantage fine thread has is tensile strength (pulling the bolt apart literally from opposite ends). Wouldn't Shear strength depend on the material and thickness (example 1/2" grade 8 vs 3/8 grade 5) I understand if you were putting the shear load at the thread then coarse thread could be less (deeper thread cuts) but a proper sized bolt will have the shank at any shear point, not the threaded portion.
When you clamp two things like this the idea is to tighten the bolts to proof. The way the clamping works, as you load the joint there is no change in the load on the bolts. In this case the bolts stay in pure tension and the shear load is only between the clamped parts. A fine thread bolt will provide better and more reliable tension due to the way the bolt tightens.

The engineers that designed the joint choose fine thread for this reason. Normal bolts are metric coarse on a Defender. They use UNF when there is a valid engineering reason.
 
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