Hi Crew,
Just my 2c worth on things to keep in mind when getting a steerer tube
lengthened...especially if a non bike savvy metal worker is involved.
Firstly, it is best if you can cannibalise an old fork/steerer tube with
the same threading rather than having to cut threads on a fresh piece of
tube.
Make sure the cuts are perfectly square for each part. This will prevent
alignment problems later on.
The join between the steerer parts to be brazed together should not have
a sleeve behind it unless it is way down the steerer tube well below the
stem insertion level. That stem wont get past the internal sleeve
otherwise! After brazing, the steerer tube internal should be honed out
in case of any brazing/welding crud that might be hanging around the
internal tube.
Try and position the cut and braze/weld well away from where the
pressure of the stem is being wedged against the internal wall of the
steerer. This will prevent pressure being placed on the join and
possible failure of the job.
Best practice is to clean threads tap and die style before re-assembly.
Lastly, get someone who works on bikes to do this as he will have the
right tools that are required. A framemaker is the obvious choice.
Greg Softley
Coffs Harbour
Australia