Stuck stem - removing drilled out remnants of

[David9694]

On my current project someone had cut through a stuck stem entirely - pretty desperate measures if the only benefit is separating the forks from the frame. I’ve done some extensive drilling out, 13mm HSS bit and 5mm to get round the sides of the bolt and also attempting to disintegrate the wedge. The stem wedge is still holding together, but is now out of the way and is separate from the remains of the stem.

I think my next step is to gouge out the rest of the head tube with a 19-21mm adjustable ream.

Any advice or opinions?

[Brucey]

once you have got this far you can use a blowtorch to heat the remains of the stem directly. After a few hot/cold/hot cycles it will lose its grip on the inside of the steerer and will come free.

FWIW it may be a bit late now but the remains of the bolt should have unscrewed from the wedge. Once the bolt is out of the way and the wedge is knocked down you ought to be able to use a padsaw to slit the remains of the stem. Provided you don't cut into the steerer this is a good solution too.

The other thing that will help to release the stem is good old-fashioned hammering; the steerer can be hammered so that it stretches the OD very slightly; not enough to affect it adversely, but enough to make the remains of the stem loosen.

cheers

[peetee]

Assuming the steerer is steel and the stem body is aluminium the stem can be dissolved out with caustic soda/ water mix. After this the wedge can be given a good douse of release fluid. The steerer is thicker guage at the lower end so the wedge needs a good whack from below to get it up and out. Threading in the (redundant) stem bolt from below can give you something to hit and a bit of waggle leverage too.

[David9694]

Assuming the steerer is steel and the stem body is aluminium the stem can be dissolved out with caustic soda/ water mix. After this the wedge can be given a good douse of release fluid. The steerer is thicker guage at the lower end so the wedge needs a good whack from below to get it up and out. Threading in the (redundant) stem bolt from below can give you something to hit and a bit of waggle leverage too.

Yes, it’s the right combination of steel and aluminium. Just remind me please what sort of concentration of caustic soda would be required?

[peetee]

Hmmm. Been a while since I did this but I think you need to try a few combinations on a scrap bit of ally.
It goes without saying but wear protective gear as you can get random pockets of bubbles that break free and spit the stuff everywhere.

[Gattonero]

On my current project someone had cut through a stuck stem entirely - pretty desperate measures if the only benefit is separating the forks from the frame. I’ve done some extensive drilling out, 13mm HSS bit and 5mm to get round the sides of the bolt and also attempting to disintegrate the wedge. The stem wedge is still holding together, but is now out of the way and is separate from the remains of the stem.

I think my next step is to gouge out the rest of the head tube with a 19-21mm adjustable ream.

Any advice or opinions?

It sound pretty bad, have you checked the ID of the steerer form the bottom? A little rust is normal, a lot of rust is not good if has gone up to reach the stem's wedge.
If the wedge is not too low on the steerer, you should be able to use a small (hand-held) propane torch and not damaging the paint, just don't get the metal red-hot.

[MikewsMITH2]

Have done the caustic soda trick a few times. It works well and is great fun. You can buy lye off eBay. Crafters use it for making their own soap. You need a tall slim vessel and add the crystals until they won’t dissolve any more. Put the steerer into the vessel in a plastic bucket as it will bubble over. Then sit back and watch the fun. You may need to change the caustic solution a couple of times if the bubbling stops. You will hear the stem wedge fall to the bottom of the vessel when done. Very satisfying.

[gazza_d]

I had a stuck stem, and hacksawed 2 slots at 180' to each other.
Once almost through I was able to crush with a pipe wrench (no vices here) and twist the remains out easily.
I had left a fair bit sticking out above the steering tube though.
New stem has been liberally lubed up

[MikeDee]

From Jobst Brandt https://yarchive.net/bike/frozen_stem_remove.html

[Brucey]

FWIW some forks (eg with parallel-sided brazed fork crowns) can be clamped in the jaws of a small-ish bench vice; the fork blades straddle the throat of the vice. The allows brute force to be used without risk of damage to the fork blades.

The other main point that has been missed is that the crud occupying the space between the steerer and the stem can be mostly (by weight) water. The soaps used as grease thickeners (once the oil has run out of the grease) and the metal oxides formed via corrosion etc all have a ferocious appetite for water.

It takes sustained temperatures well over 100C to drive this water from the joint at any speed, but there is no doubt that the seizure is weakened by heat cycling. Not only does the oxide dry out and shrink, but the aluminium stem expands against the steel steerer (there is a considerable CTE mismatch) and may yield as a result (the strength of any aluminium alloys is appreciably lower at 200-300C ). Once it cools down again the stem is unlikely to be gripped so firmly.

Note also that the hot stem must expand lengthwise too; this cannot happen unless the bonds of corrosion are to some extent broken.

If you have access to liquid nitrogen the freezing action helps to break the bonds of corrosion and the differential CTE ensures that the aluminium stem shrinks away from the steel. The differential CTE is about 7 ppm/C, so a 200C temperature change will cause the stem to heave vs the steerer by ~30um, i.e. more than enough to cause the parts to loosen.

FWIW water/sweat ingress into the joint can be largely inhibited by fitting a tightly-fitting plastic washer to the stem just above the locknut (see the 'supercommuter' thread). The space between can be coated in waxoyl (or similar) so that it is rendered hydrophobic. This deters water ingress. To prevent the top of the stem from moving around(which as JB points out can pump water into the joint), it is not a bad idea to wrap a few turns of PTFE tape round the stem before lowering it to the correct height; this can prevent water ingress too.

cheers