Originally Posted by
unterhausen
There's a reason why fork fixtures cost $1000. Call me crazy*, but I decided to spin the fork. Chuck up the steerer, make sure it has minimal runout, and drill out the steerer. The fork will be left sitting on the drill bit. There will be a speed transition, but I would do it pretty slowly anyway.
I don't think that would work for my fork, because it has a divot in front for the tire clearance, like some track forks.
That would make the drill wander towards the front of the crown. Even a drill that large is flexible, especially with that much stickout. Also drills don't make holes that are particularly round, or to dimension. I could see doing it with with a solid-carbide boring bar, but for one that large diameter and longer than the forkblades to reach the crown, I'd have to mortgage the house.
My fork-brazing fixture was free because it was given to me (thanks Alex!!) but I think they'd never cost more than a couple hundred if I had to buy everything. Anyone know what a Wetmore jig costs to make? A few pieces of 80/20 extrusion and some fasteners, a dummy axle and a little machining. Not the greatest fork jig but more than adequate for a hobbyist.
Anyway the fixture I envision for the lathe would be much cheaper, since I have enough scrap steel to make it, have a dummy axle etc, so it's just my labor, which is worth nothing!
Probably cut off the steerer at the crown after indicating in the steerer.
Yes that is my plan. I'd clamp the crown to my fixture with the steerer held in a 5C collet in the spindle, shimming the crown until the fixture and collet "agree" with the fork clamped tight. Then cut off the steerer at the crown top, probably leaving just a bit of steerer as a visual doublecheck that I'm boring on the same center. If it's off, I would have a few mm to notice and correct before entering the crown hole.
The other end of the fixture with the dummy axle would have a center hole drilled in it and held precisely on-center by a dead-center in the tailstock, at least for the starting position, tho of course once I start feeding the whole shebang towards the boring bar, the tail support would go away. The tail center would just be for the initial setup.
It occurs to me that Columbus's rifling would make indicating on the inside of the steerer impossible. It makes me laugh they are still doing that.
*People always think spinning the fork is crazy. Never had any problems with it. Consider this bad advice.
Agreed on how dumb that rifling is. As John Oliver likes to say, "how is this still a thing?"
I got no problem with spinning a fork though. That's how I cut crown race seats. The Campy-style cutter is for people who don't have lathes. I pity them!
