My EBB bolts not so good?

[mountaincarrot]

Mechanical enginering types, or perhaps Andy/Robin ?

Is it likely (I hope) that the EBB locking bolts on (eg) Enduro frame are softer material then the nuts they thread into?

My secondhand Enduro frame (very nice 5000KM last year), needed it's EBB bolts lubricating. Upon their complete removal I realize the threads are partly stripped. Clearly sometime during their lifetime they have been over tightened. They still seem to be working, but I put them back gingerly without using the 10NM (min) suggested. Seems OK after a quick ride, but I'm now concerned the EBB insert might slip round because of inadequate retention.

I see replacement EBB bolts are available from Thorn. I'd like someone who knows to reassure me the welded nuts are of harder material then the bolts!

[Chadlington]

I'd also appreciate a view on this....

[freddered]

It seems incredible that they are stripped, they are quite substantial bolts.

I'd have thought you'd completely puncture the soft rotating EBB holder before you stripped any threads.

You only need to 'nip' the bolts tight to secure the EBB so I wouldn't worry about it slipping (it's no disaster if it does really, just tighten it a bit more.  My bolts aren't done up with much pressure.

[expr]

The bolts as far as i know are made from stainless steel, although I'm not sure as to what grade ? Have the threads on the screw started to go or on the female thread in the bb. I have allready thought about this issue happening and desighned my own bb thread replacement inserts so if the thread goes then i can replace the insert with a new one.

[expr]

The other option open to you would be to use a helicoil kit if the threads have gone in the bb. The helicoils are made from hardened stainless which usually perform much greater than the material they are put in to. This type of thread repair is usually as far as you need go and is much stronger than the origional one. The reason I decided to make mine totally replaceable was more for peace of mind and also looks as I have mirror polished the new stainless steel thread sockets.

Regards expr

[Chadlington]

Thanks, luckily mine are fine :-) But, it's the only part of my Thorn I fear for most....

[expr]

I would'nt worry to much, the amount of force required to pull threads out of the bb is quite alot. If the bb threads totally failed then new nuts could be welded to the frame anyway. And if you know a good engineer he could easy make you replaceable nut inserts like the ones i have made!

[expr]

I can't seem to post any pictures at all they are around 500 kb, i have4 selected the picture using aditional options and then tried to up load but then it says the file might be to big ? can any one suggest what I might be doing wrong please,

[stutho]

The Attachments folder is full - I will ask SJSC if we can have a bit more spaces on there server!  However in the mean time you can still add photos that are hosted elsewhere.  I use photobucket.com - it free.    (There are lots of other photo hosting sites).

Regards

StuTho

[expr]

here is the link to the pics for the modified screw threads.  http://www.photobox.co.uk/album/104559156

This shows the new insert holders being made from a solid bar, and then put in the lathe for the center hole and counter bore for the new insert lip which has been made as a top hat shape. The insert is a press fit with a little loctite retainer so to remove it for a new insert to be fitted you simly tap out the old one and push in a new one from the inside of the bb .

All made from 316 stainless steel, mirror polished and tapped out to accept the standard m8 fine threaded screw. After the tig welding to the BB I have then primed the shell and then airbrushed in a single pack jet black base coat with a single pack clear coat finish, allowed to dry and then fine polished with G3 cutting compound. Also included a little peep into what's inside the hub for those of you interested.

[mountaincarrot]

I bought 2 new Thorn bolts and they seem to be holding fine at (or just below) the required torque . Inspection of the threads indicated the old bolts had indeed come off worse than the female threads in the frame.

[expr]

That's good news, I found out just out of interest that both the m8 fine screw and the female threaded boss on the bb shell  are both stainless steel.

just a little point for those of you who feel the torque req'd to keep the bolts tight is a little to much.

Set up the ebb to where you require it, use the screw to mark the ebb and leave an indent then remove the ebb from the shell and use a punch or carfully use a 6/7 mm drill to make a definate indent in the ebb, then reinstall the ebb into the shell and then add a little loctite blue threadlock and lightly tighten the screw back into the shell, this way you have a definate indent to stop the shell moving and the screw cant come out with little force on the threads etc..