Who the HECK.......

[CJim7]

...created fine thread bolts and why the heck do they have any purpose on my CJ7

The definition of "eternity" is tightening a nut down on one of these things

 

[mylittlecj5]

they can take a higher load on the threads than a course threaded bolt, much like 35 spline axles are much stronger than 19 spline ones!

Or, they just do it to torture you!

 

[Fifesjeep]

Don't be fooled by the spline counts... You have to realize that, with automotive parts the different spline counts come with different diameters.... Now, If a 19 spline shaft had the same working diameter of the 35 spline shaft they would almost mirror each other in strength... the difference is so minimal that it would come down to $$$.... and honestly the real difference and true deciding factors are time and money... It's much easier, faster and cheaper to roll splines than cutting them.
Think about all of the large machinery that have tons of torque that use large splines. How often do you see them breaking?
Me personally, I've machined both.... I can't wait to cut some more...

 

[Kane]

Aren't fine thread bolts able to hold a specific torque value without loosening better than a coarse thread?

 

[Cheepjeep85]

yes ^^^ that was always my understanding they are stronger. more threads more bite.

 

[CJ]

they can take a higher load on the threads than a course threaded bolt, much like 35 spline axles are much stronger than 19 spline ones!

Or, they just do it to torture you!

Aren't fine thread bolts able to hold a specific torque value without loosening better than a coarse thread?

yes ^^^ that was always my understanding they are stronger. more threads more bite.

Higher surface contact area per diameter = higher stress leveling.

You all are kinda right...

 

[Cheepjeep85]

three collective minds got it right

 

[ftwflh]

Fine thread bolts and nuts are less likely to back off and can be torqued more accurately.I run fine thread with nylon lock nuts on everything I can on my old Harley and I dont have any problems with things loosing up.

 

[gert]

:laugh::laugh: yep they are great until they rust then they are a mother....

 

[CJim7]

Thanks for the insight, makes sense about strength and load dispersion.

Seems other then the crank dampner bolt, the only other place I've found so far that uses them are at the motor mounts and engine frame brackets. One of the hardest places to get wrenches on.

I almost wonder why headbolts aren't fine thread...

 

[iCEMAN]

Fine thread bolts and nuts are less likely to back off and can be torqued more accurately.I run fine thread with nylon lock nuts on everything I can on my old Harley and I dont have any problems with things loosing up.

Oh yeah, Nylok nuts, fine thread bolts and old Harleys are made to go together.

So what year do you have (old Harley wise)

 

[ftwflh]

Oh yeah, Nylok nuts, fine thread bolts and old Harleys are made to go together.

So what year do you have (old Harley wise)

I have a 1972 FLH that has been through 4 wives and still loves me

 

[IOPort51]

Lets not forget about after market suspension U bolts. Fine thread, lock nuts, on your back. over head and about three feet longer than they need to be. The reason I own compressed air and an air ratchet.

 

[CJim7]

Lets not forget about after market suspension U bolts. Fine thread, lock nuts, on your back. over head and about three feet longer than they need to be. The reason I own compressed air and an air ratchet.

aggh...I forgot about those

 

[Fifesjeep]

I almost wonder why headbolts aren't fine thread...

They don't need to be as they're not practical for that application. The coarse threads matched to the diameter and grade of the bolt easily exceed the required torque loads. The finer threads would be complete overkill and a waste of time/money.