Crankshaft - damaged thread on clutch bolt - what to do ?
Turbo Mini Forums

I have damaged the threads on both the bolt and crankshaft while removing the clutch. (bouh !!!!)

I was considering installing an helicoil (do you call those this name over here ?) and renewing the bolts as those have to cope with a momentum througt the spacer more than anything else.

Would you guys agree with that ?

Alternate option is to re-tap the threads in the crankshaft and fit a new bolt.
=> not favoured because I don't have such tools at hand.

Alternate shamefull option is to torque that damaged bolt up that damaged hole and hope for the best
=> much favoured in a short term option but is definitely not hte way to go (still very tempting ...)

What would you do ?

And by the way , what size is this hole and bolt and what thread is it, can't find it in my documentations ?

Thanks in advance

Rusty by nature

The thread in the end of the crankshaft (both ends) is NOT a standard thread.
It is 5/8" X (something) 16tpi.
The reason for my "something" description is that it is not clear whether the thread form is Unified or Whitworth.

Most people seem to accept it is 5/8 X 16 UNS (ie, Unified Special, but NOT UNF or UNC) but I have also seen evidence it is 5/8 X 16 Whitworth special (but NOT BSW or BSF).
The difference between the two is minor (55 degree vs 60 degree thread angle) but, of the few companies that will provide a specialised tap, the majority say 5/8" X 16 UNS.

Whatever you may choose to believe, 5/8" UNF is 18tpi, 5/8" UNC is 11tpi, 5/8" BSF is 14tpi, 5/8" BSW is 11tpi, but the thread in the crankshaft is 5/8" by SIXTEEN tpi, which is none of the above, so it's truly a "special"...

One of the USA Mini suppliers has 5/8"X16UNS off the shelf, advertised for just this purpose.....

Rod.

Schrödinger's cat - so which one am I ???

Thread is Whitworth?

Smith and Bullough in Bolton might be able to sort you out with these od thread sizes

http://www.smithbullough.com/smithbullough.html

Edited by Sprocket on 4th Jan, 2008.

Schrödinger's cat - so which one am I ???

Here was the only place I could get it "off the shelf" but it's USA so add import costs.
http://www.minimania.com/web/Item/18G1128/...h/InvDetail.cfm
I believe that the part number they are using (18G1128 ) is the original Churchill special tool part number...

Schrödinger's cat - so which one am I ???

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=173244

The search function could be rather useful sometimes!

I wasn't a member of this forum when I was searching for the information 6 months ago !!!!

Schrödinger's cat - so which one am I ???

I had the same problem a few weeks back, I ran a tap down the thread and it sorted them out a treat.

I think minispares may do an extended bolt aswell if the threads are really bad, can't remembr if its the flywheel end or damper pulley though.

https://www.facebook.com/pages/Fusion-Fabri..._homepage_panel

www.fusionfabs.co.uk



1/4mile in 13.2sec @ 111 terminal on 15psi

Minispares do an extended bolt, but it is intended for the damper end, and is longer to give more thread engagement, as the standard one doesn't give that much, and can also start to bottom out on the radius/unformed threads directly under the head before it really puts that much axial load onto the pulley, possibly leading to it coming loose. The Minispares one comes with a thick washer to stop the radius under the head of the bolt bottoming.

The easiest way on fixing the damper end, is to fit a flywheel bolt

The offer of the loan still stands, though with only 11 posts I would be asking for a small refundable deposit.

Thanks Matty it arrived back a couple of days ago.

We supply the correct tap for the job which is 5/8 16UNS the taps are £46.00 plus vat and postage

http://www.avonbar.com

from stock.

http://www.avonbar.com

Wish i'd know that about 6 months ago, though a similiar price to having it shipped from america.

Half the price of minispares!!

Also Avonbar Racing, any chance of an update on when i'll recieve my online order (order no. 3003476), Cheers.