Fine thread bolts vs coarse

[John S-B]

Are you guys replacing broken/stripped bolts with the same sized fine thread bolts, or are you switching to coarse? Fine thread are much harder to find off the shelf, although I do have a Fastenal fairly close. Sometimes they only offer stuff in large quantities, and they close at 5. I assume the military spec'd fine thread for the holding power to resist loosening from vibriation since there aren't a lot of lock washers on a lot of the body bolts. But with thread lock I'm wondering if it will matter if I just use course thread bolts. They'll be a lot easier to find in the same size. Have any of you done this? Are you noticing any problems with loose bolts? I'm going for a retro Vietnam era look, but I'm not going for museum quality resto.

 

[JCKnife]

I've been using fine-thread bolts from Mcmaster-Carr.

I think before it's over with, I will have spent more on bolts than I did on the truck from GL (in all seriousness).

 

[clinto]

I use fine thread (even for my modifications) as I want to keep the vehicle as close to "as built/designed" as possible.

Luckily, there is a Mom and Pop style hardware store near me with a great selection of fine pitch grade 8. Expensive, but what isn't.

 

[nk14zp]

Fine thread here also.

 

[willy]

As a general rule when a bolt goe into some thing it is coarse tread
And when 2 pieces are bolted together it is fine
Now if you want to change all off your bolts you better not sell the truck because the next guy will have a problem off knowing whether it is coarse or fine.
Willy

 

[frodobaggins]

I use coarse thread, no problems.

 

[joshs1ofakindxj]

Course thread here also.

This is what I was told:

If you want to put it together once and never take it apart, then fine thread. If you plan on taking it apart again and again for maintenance or whatever, then course thread.

 

[steelandcanvas]

When I remove any bolts, I usually run them across the wire wheel and then chase the threads with a die, or a tap for a hole or nut if they need it. A little anti-seize on the threads and it's ready to re-install. I might replace a fine thread with coarse, but only in a pinch, there is a reason the engineers chose fine thread hardware.

 

[Wildchild467]

I used as much fine thread as i could when i rebuilt my deuce. i put antisieze on some threads and used lock washers. some things i did not want the goopy antisieze on it, so i used a tacky penetrating teflon lube instead. it seems to work good. even if i dont plan on taking it apart again, i dont want any problems if i do. i have also used fine thread ny-lock nuts too. its not 100% Original, but being fine thread is close enough for me.

another trick i did if i used nuts with no locking feature is clamp the end of the bolt lightly with a pair of visegrips. you cant really notice it and it just deforms the threads a little that if the bolt comes loose, the nut will not come off. yet if i want to take the nut off the bolt, a pair of wrenches will do the trick.

Those are just some of the things i did. to each their own. thats they make vanilla and chocolate

 

[m816]

I also chase the threads on every bolt I remove and chse the threads witha die if needed. Every bolt I remove gets anti sieze in it, no matter what. You never know when you will have to take it apart again. Especially when it is easier to remove three thigs to get at the one thing you have to work on, Look around, you can always find a supplier of finethread bolts either locally or on line. Stop shopping at Home Depot, When you shop at Home depot, you get cheap. When you get cheap, you wind up painting your deuce with house paint.. Don't paint your deuce with house paint

 

[mistaken1]

From what I have seen most of the nuts are deformed thread reversible lock nuts. The manual says to replace them with new.

I will match whatever is replaced.

This is more money up front but the per unit price beats the heck out of home despot.

Bolt Depot - Nuts and Bolts, Screws and Fasteners online

 

[wsucougarx]

I use fine threads on everything. Peace of mind for me.

 

[SCSG-G4]

Fine threads are used because the root diameter (the part without threads inside where it is threaded) is larger on bolts of the same outer diameter, while the bearing surface (the part where the threads touch) remains the same as coarse threads. For the same metal characteristics, that results in a stronger bolt. For example, a 1/2 inch grade 8 coarse thread bolt has about the same strength as a 1/2 inch grade 5 fine thread bolt.

Do as you think is right, as for me, I'll continue to use grade 8 fine thread bolts whenever I can.

 

[quickfarms]

Home depot only sells cheap low grade bolts. They are great for bolting wood together but not so good on a truck. The markings on the head of the bolt indicate the grade.

If the bolt is replaced I use the same thread, pitch and grade as they built it with.

 

[renovate7]

I don't think the poster was talking about putting a course bolt into a fine thread nut...When i'm replacing a nut bolt combo I use course thread and a lock washer.
Tractor Supply is an excellent place to buy bolts. They sell them by the pound, way cheaper than any big box. They even have grade 8, which I use most of the time.

 

[Tinwoodsman]

I used fine thread. I get them at my local welding shop or NAPA. Good luck.

 

[0352]

Fine threads are used because the root diameter (the part without threads inside where it is threaded) is larger on bolts of the same outer diameter, while the bearing surface (the part where the threads touch) remains the same as coarse threads. For the same metal characteristics, that results in a stronger bolt. For example, a 1/2 inch grade 8 coarse thread bolt has about the same strength as a 1/2 inch grade 5 fine thread bolt.

Do as you think is right, as for me, I'll continue to use grade 8 fine thread bolts whenever I can.

This is 100% right because there is more surface area along where the tread touches, and that drastically reduces the shear force along the normal of the bolt. Always use fine thread nuts and bolts when you are securing two plate structures together.

 

[197thhhc]

I use fine thread on all deuces we work on to sstick with the original theme of the truck. I would use coarse thread on add on parts on my truck. When I put on my remote reservoir I used coarse thread bolts. Look around a little and you will be able to find the bolts and nuts cheaper.

 

[Katahdin]

I use my judgement, I try to use the original bolt type but sometimes you can't find or wait for an order of grade 8 fine threaded bolts. What ticks me off about rusty fine threaded bolts is the threads can break and the bolt just spins in place. Good if you want to keep the part together, bad if you want to remove the part!

I recently did a tow hitch install and noticed the Curt 18,000lb trailer hitch and Reese 16,000lb ball and pintle both came with grade 8 coarse threaded bolts for the install. The ball however was fine threads. If grade 8 course threaded bolts are good enough for towing...well....? I do make sure to use lock washers or thread locker after a bad experience loosing a leaf spring bolt on a trailer once.

 

[gimpyrobb]

John, make a trip to Mendleson's on 1st street in Dayton. All their hardware is $1 a lb. Doesn't matter if its grade 10, fine or coarse, titanium, or whatever.