Three videos, the first is just a milestone for Karen — your stick getting its first cuts. The second shows a little more of the stick. Third, the joint pin.
One appreciates geometry when making sticks out of several pieces of wood.
On this video you can see how one section (the part being cut) appears to have a giant wobble, meanwhile, the part you see enter the screen on the left, between 19 -24 seconds, has no wobble. The reason isn’t what would come to mind first: a misalignment of the parts. That could be it, but in this case, the apparent wobble is due to that section having been turned on a different axis than the stick is turning on now.
Why’s that?
Usually, my first cuts after glue up, the goal is to get the stick turning on the only two points it will turn on for the duration. One of those is the hole at the small end, where the joint pin will go. It’s already drilled, bored, and tapped before the stick is assembled and glued. It has to be a center, otherwise the stick will wobble.
The center at the fat end doesn’t matter, for the moment. It just has to be close.
(Ultimately it matters as much as the center of the joint pin hole, in that it has to be on the line formed by the joint pin, or else the stick will wobble. That’s kind of a theoretical point to make, as no one’s ever going to x-ray your joint pin, draw a line, and ascertain how many thousands of an inch you’re off, 28 or 30 inches down stick.
The deeper point is valid, however. The joint pin doesn’t just have to be on center, it has to be on center all the way in, and if you extrapolite its line, that needs to be dead nuts the center at the fat end of the stick too.
That’s one reason I’ll likely never put a runout gauge on a joint pin to show off how straight it is. Unless you put the gauge on every point on the line, you don’t know if the pin’s axis is perfectly centered on and aligned with the stick’s axis. The only way you really know, I guess, is to roll the stick.
A side note, since it’s getting deep anyhow — it’s possible for the joint pin to be way off and still have a straight stick. The shaft would wiggle as it’s being screwed to the butt, but if the stick was turned as a single piece it could still be straight. The technicality disproves my main point, but even though the stick would be straight, who the hell’d want it?
Too much inside baseball.
Anyhow, I turned that section with the apparent wobble while the fat end of the stick was in the chuck, but hadn’t yet been turned so the outer diameter at the fat end was concentric with the actual center hole.
After I reversed the stick and put the skinny end in the chuck and the fat end at the tailstock, I turned the fat end off its actual center. This (making it ’round’) allowed me to flip the stick again, and now in the video here, I’m turning off the fat outer diameter, which I can now trust, and the joint pin hole, which is as perfect as is possible before the joint pin goes in.
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