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-   -   Repairing Bulged Steerer tube (https://www.bikeforums.net/framebuilders/1227032-repairing-bulged-steerer-tube.html)

duanedr 03-29-21 12:55 PM

Repairing Bulged Steerer tube
 
Thought this might be interesting. I had to extract a stem from steerer on an early 80's Columbine. The prior owner buggered up the Campy SR headset obviously not knowing what they were doing. Well, I did what you all would do to extract a stuck stem and after a few whacks it came loose. Since the HS was loosened, I thought I'd clean it out and re-grease and adjust it. As I had the fork out, I noticed a bulge where the wedge would have been. It took me about an hour to get down to a bulge of around .004-.005" and I felt like that was close enough - until I didn't. I took another run at it and it's now within a few thou variance like the rest of the tube. The HJ crown was also drilled off center as you can see in the 3rd photo. I'm sure this was done to take an internal/modern brake nut. I'll chuck this up in the mill and enlarge it and then make a shim that sits in there straight. There are other issues....

Initial measurement:
https://live.staticflickr.com/65535/...2d26a629_c.jpgFixing a bulged steerer tube. by Duane Draper, on Flickr

You can see how my blocks took a bit of a beating as I rotated the fork and clamped down on the bulge.
https://live.staticflickr.com/65535/...172486ac_c.jpgFixing a bulged steerer tube. by Duane Draper, on Flickr

Showing it who is boss. The wood was so soft, it didn't damage the paint around the crown.
https://live.staticflickr.com/65535/...e0c2c563_c.jpgFixing a bulged steerer tube. by Duane Draper, on Flickr

unterhausen 03-29-21 03:33 PM

Duane, when you made the tube bender I see on your flickr, did you turn the die too?

duanedr 03-29-21 09:51 PM

Yes. It's for a 7/16" tube for curved bridges. I have a round carbide insert tool that is just slightly smaller than 7/16" so I had to sort go in from the right, then the left and then back to the right and then compare to the tube and make further cuts from there. It wasn't too bad. I happened to have picked up a few 2"-3" rounds that were nearly perfectly .500" thick with 1/2'' hole. The handle part needs some work. The follower slips and doesn't follow the curve well which causes the tube to kink.

unterhausen 03-29-21 10:19 PM

That's too bad about the follower. I want to make a King Cage style bender that has multiple dies so I can make a rack more easily. There are programs that will tell you how to move a lathe tool to follow a curve like the one needed for a die, but I haven't tried any of them yet.

But thinking about it, King Cages have bends that are a little squished in places.

duanedr 03-30-21 12:56 AM


Originally Posted by unterhausen (Post 21991192)
That's too bad about the follower. I want to make a King Cage style bender that has multiple dies so I can make a rack more easily. There are programs that will tell you how to move a lathe tool to follow a curve like the one needed for a die, but I haven't tried any of them yet.

But thinking about it, King Cages have bends that are a little squished in places.

Yes, I have a large (12"x12"x1") plate of stainless that has a bar across the bottom and I clamp the bar in the vice and it makes a nice work table for brazing small bits. I have holes in it where I mount my fork blade bender and small 1T arbor press. The goal is to make a small Diacro-like bender for racks, curved bridges and other small bits. Once I get the follower figured out, i think it'll work really well.


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