Star Fangled Nut Problem

[Christophe]

Just giving the Trucker an overhaul and want to remove the fork to clean and regrease the headset.
When I undid the headset nut it felt a bit tight but now when I inscrew it just turns without coming out. It feels like the nut is just turning which leads me to believe the screw bit in the star fangled nut is broken. I cant drive it further in to the fork as the headset top cap is still in place together with stem and spacers. Also will now not tighten up.
How am I going to get it out. Will it come out through the top if I try to drive it out from the bottom? Any other ideas?

[Jurek]

[strokeschin]
Interesting one.....
[/strokeschin]
ETA - it won't come out if you attack it from beneath - it'll just dig deeper into the internal bore of the steerer.

Have you considered a new frame/ forks?
*runs away*

ETFA - I'd suggest drilling off the head of the bolt, removing the top cap and then drifting the severed bolt and star-fangled whatsit further down the steerer.
The problem with this is that if the bolt is turning, you're never going to get a drill bit to 'bite' in it.

[LittleWheelsandBig]

You can always drill off the head of the bolt (if you can wedge the bolt from turning from the top or bottom) and continue on from there, but that is pretty drastic.

[Jurek]

LWAB has read my branes while I've been typing!

[Paul H]

I'd sacrifice the top cap to remove the stem and spacers, you'll get a better idea of what the problem is.  The bolt may turn if you're pulling it at the same time. If that doesn't work then unless the bottom of the steerer is blocked it should be possible to knock it through, I've done so with a couple.  I'd have thought trying to knock it out the top, against a tightening star nut would be difficult to impossible.
EDIT - or as Jurek and LWAB say sacrifice the bolt instead of the top cap, but I'd rather leave the head to grip. Also cutting through an aluminium t cap will be easier than drilling out a SS bolt...

EDIT, EDIT - if you do this and then need a new cap, I've got several knocking around and am happy to stick one in the post to you.

[Jurek]

I think the easiest scenario may be a sacrificial top cap, sacrificial stem (it's not exactly an expensive component - usually) and an angle grinder with a 2mm cutting disc.
Job done.
Drastic maybe, but a comparatively swift solution.

ETA - Currently dwelling on this - maybe it's not so clever.....

[Paul H]

I think the easiest scenario may be a sacrificial top cap, sacrificial stem (it's not exactly an expensive component - usually) and an angle grinder with a 2mm cutting disc.
Job done.
Drastic maybe, but a comparatively swift solution.

ETA - Currently dwelling on this - maybe it's not so clever.....

The caps are pretty flimsy, once you've got one cut a pair of mole grips is enough to break them up.  Not pretty but shouldn't be any need to damage the stem.
just PUT THE POWER TOOLS DOWN

[Jurek]

 

[rogerzilla]

The technique to get an unwanted SFN out, assuming that's the root cause, is to drill through the top part of the nut.  You can then knock the bottom star away from the top star, tap each star on its side in turn and pull them out easily with needle-nosed pliers.   I did this a few months ago on a s/h pair of Kona threaded forks that some philistine had used with a threadless headset.  Amazingly, the threads weren't damaged.

[Brucey]

the centre part of the SFM is meant to be riveted to the upper and lower stars. If it starts to seize to the bolt it will turn when you try to undo the bolt.  Two suggestions;

1) once the tension is gone the bolt may unscrew OK. To remove the tension, chop out a spacer from beneath the stem, eg by hacksawing half way through and then breaking up with a screwdriver.

or

2) bring something (ideally a length of tube of the same diameter as the centre part of the SFN) to bear against the underside of the SFN an then see if you can get enough purchase to help the bolt unscrew.

also

3) if the bolt has no tension on it then waggling it sideways may help it come loose enough to unscrew  OK

cheers

[Christophe]

OK. Cheers chaps. Had a bit more of a twiddle and the threaded bit in the nut definitely feels like its just spinning freely. So
Plan a. Give it a whack from underneath to see if the star fangled bit grips the thread enough for me to undo the bolt

Plan B. Get the drill out and attack the bolt and/ or top cap. From there I can push the old nut through and install a new one.

LWAB. The idea of the overhaul was to refresh my current fleet and not give me any more ideas regarding buying yet another new frame!

[Torslanda]

MOST top cap bolts are stainless, given that it's spinning in place you've got two problems.

The bolt is very hard AND you have no way of holding it while you drill.

Destroy the top cap and replace the lot.

[quixoticgeek]

I had a similar issue. Discussed in this thread here: https://yacf.co.uk/forum/index.php?topic=106083

In the end we drilled out the bolt, hammered the star fangled nut down into the tube, and then fitted a BBB power head instead.

I am not impressed with the failure modes of the star fangled nut. Won't be using them again.

J

[zigzag]

i would try to extract the sfn from the steerer, as it would keep bugging me if it's pushed down serving no purpose..

there is always a way, especially with the almighty tools like a mini grinder

[Brucey]

if you are dealing with a steel 1-1/8" steerer then there is a simple solution involving (ahem) a big hammer....

Get a length of tubing (ideally steel) which is just small enough to be inserted into the steerer from below. 7/8" or 15/16" OD tube is usually about right; the steerer bore is nominally 1" but the bottom of it may be distorted from welding or have burrs from being drilled.

Invert the bike, place the tube in contact with the underside of the SFN, rest the top end of the steerer on a piece of wood (with a hole drilled in it, big enough to accept the M6 bolt), and simply start boshing away.

 The lower part of the star will soon release its grip and in fact at this stage it may bind onto the threaded centre well enough that you can undo the bolt like you should be able to.

If this does not happen then continued boshing will do one of several things;

-it may collapse the lower star so that the tube bears against the upper star and releases that too

- it may cause the upper star to start to slide in the steerer

- it may collapse the upper star anyway.

If the bolt comes out and the upper star is still gripping the steerer, it can usually be pryed one petal at a time using a screwdriver so that it loses its grip.

This method should not be attempted with an aluminium steerer; you will just damage the inside of the steerer too much.

If successful this method leaves no junk inside the steerer tube.

cheers

[Christophe]

OK we have success.

Not as problematic as first thought. I managed to get a screwdriver under the top cap and prize the sfn out of the steerer. As suspected the thread bit had completely seized on to the bolt and was spinning freely in the centre. Glad I didn't have to resort to more desperate measures.

Thanks all for your tips.
Cheers
Chris