This article on the process.arts website has step-by-step instructions for making accurate B&S joints using only a drill-press, some common hand tools, and an inexpensive Chinese-manufactured self-centering chuck. It includes instructions on how to drill and tap the ball and silver-solder the rod into the ball, and links for materials and tools.
Thanks for posting this. I've been using threaded brass balls, but I'm limited to the available sizes. This looks like a good way to drill steel balls. I might give it a try if I can find the chuck from the tutorial.
This is a link from the old board showing a couple of jigs for drilling balls that don't require a chuck. Instead, you can use bar stock.
The here's LIO's tutorial from StopMoWorks, also done with bar stock:
This may help. It is a slideshow with narration showing how to make a ball and socket armature with hand tools, lamp parts and aluminum. I shot the slides and wrote the narration for this many years ago, but just recently put everything together. Not the best presentation, but worth watching.
Ok, since we seem to be collecting techniques and tricks on this thread, here's my ball drilling jig:
The picture links to my brief article explaining how it works and how to make it. This comes from a suggestion by Trickfx on the old board, and I present it as an addendum to LIO's excellent series of tutorials:
It lets you easily file a flat surface onto the top of the ball. Once you get the rig centered under the drill chuck lock it in place and drill ball after ball - they'll all have perfectly centered holes.
One thing about the tutorial posted at the top of the page - it seems like a very good approach, but I'm not sure about the way he files the inside of the sandwich plates down. That seems like bad news to me - it's not precise enough. I think the idea is the ball has to be sandwiched between exactly matching planes with exactly matching holes drilled in them so the pressure remains precisely balanced. If the sandwich plates tilt a bit then the joint won't track properly.
I could see creating stepped shapes like that if you're using a milling machine that can make them all exactly identical, but filing by hand seems like it would result in too much imprecision.
Just because one is filing by hand does not necessarialy mean it is not to a high level of precision. It depends on who is doing the filing, the condition of their tools, and how many beers they have had in the previous few hours. If you do sloppy work, then you are definitely correct. I may be off track (forgive the pun), but humans are capable of amazingly precise work when doing things manually. A good case in point are paper makers, who can level a screed (I think that is what it is called) of paper to a thousandth of an inch. Granted these are highly experienced professional craftspeople, but they do make my point. Also it depends on what level of accuracy is needed.
Anyone have more information/knowledge on this?
I know that's true, that very experienced craftsmen can achieve great precision - but this is a tutorial and he failed to mention exactly how to achieve that precision or even that it's important. I wonder if he's even aware of the importance of keeping one single level plane across the contact surface?
Then again I might be wrong - maybe you can be off by as much as a quarter of an inch and still get good smooth tracking? I don't know - I've never tried filing down parts of my sandwich plates like that. But I did once screw up somehow - I suspect I accidentally put two plates together that weren't drilled together (I used to drill several sets of plates and keep them screwed together, but when I made Ahab's neck joint I ended up with several different attempts and think I put 2 mismatched plates together). That joint never did track right at all, and I mean it was bad! When I'd try to move his head straight up and down in a nodding motion it would fight me terribly and I'd always end up with a side-to-side motion added in no matter what I did.
Something similar can happen if you're beveling the edges of your holes to try to make them like pseudo-sockets (as in actual ball and socket joints, rather than the simple open-hole method). Unless you can bevel them all to precisely the same depth it can throw off your tracking.
From my admittedly basic understanding, I think unless you're able to ensure exactly the same treatment applied with great precision to each hole, then you're better off to keep the original straight planar surface of the sandwich plate untouched.
Of course those who know better may correct me on this.
Ok, in thinking about it, it's possible the accuracy of those inner plate surfaces isn't all that important. As long as the holes are all drilled accurately then the screw (or screws) will pull the plates tight against the two balls and create a sort of self-leveling effect (probably not the best term for it). I suppose there's a bit of leeway for slop on those inner plate surfaces. Of course I don't know unless I actually try it - but it seems to be working for him. And the fact that he didn't mention any need for accuracy there indicates that he doesn't seem to think it's important.
In fact it looks like he slightly angled the surfaces out away from each other - so that the outer edges are wider than the inner edges (if that makes any sense). He said it was to give extra room for the rods to swing around, but unless he angled them then it wouldn't do that at all - it would just allow the plates themselves to be thicker in the middle while reducing overall bulk of the joint.
I don't know what effect angling the plates outward like that might have on tracking - possibly none, or possibly a profound effect (or just a slight one - I just don't know).
Uncle LIO, where are you when we need you? Trickfx? Somebody?
As long as the holes are all drilled accurately then the screw (or screws) will pull the plates tight against the two balls and create a sort of self-leveling effect (probably not the best term for it).
I think that's correct, but only if the socket is milled. If you look at fancy machined joints on Coraline or Corpse Bride you'll see that they don't have a plane for the ball/socket contact point. I'm assuming they have nicely machined sockets where the entire surface of the socket touches the ball.
I'm not that good. Sometimes I use ball nose end mills, but I rely on a standard hole for the actual joint. The ball nose milling is there to dig out metal so that there's a lot of plate wrapped around the ball keeping the plate stiffer while keeping the profile of the joint smaller.
Yeah, I have seen angled facings like that on the professional, milled-out b&s joints for sure. Hey, one thing that just ocurred to me - I guess it's the same as if somebody uses aluminum or brass for sandwich plates and it bends a little under the pressure - you'd end up with outward-slanting face surfaces that way too. I've seen armatures like that, though I don't know how well the joints track in that condition.