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I am making a ball joint for a figure and have decided on ball bearings since they're easy to source in the correct size.

I need to attach the ball to a shaft of some sort, like a small steel rod.

The bearing will be small, approximately 1/4 inch in diameter. The shaft will be 1/8 inch or smaller.

The ball needs to be completely static and strong enough to support some weight, a pound maximum.

I have steel reinforced epoxy putty, but it's hard to work with and I can't imagine in sticking to the smooth surface of the ball.

I do not have tools to drill a hole in the bearing, and have not found pre-drilled balls of the right diameter for purchase.

What can I do? I'm looking to do this withing welding, soldering, brazing, or anything that requires high heat to accomplish.

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As much as I like the brazing answer, it's unfortunate that it won't work for your purposes.

A search using the terms "drilled steel ball" resulted in many returns for of threaded and non-threaded balls of various materials. Most of the returns are for larger than 1/4" as you've requested.

If you can adjust your design, there is a source of 8 mm drilled (unthreaded) balls on Etsy. It should be possible to use an epoxy to secure this type of ball to a rod.

drilled ball

Etsy also has a listing for a drilled threaded version.

drilled threaded ball

fred_dot_u
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    This is a great answer @fred_dot_u :) I was all constrained in "how attach without drilling" when the right answer is obviously "get someone else to do the drilling for you :) – scanny Jul 15 '18 at 18:47
  • +1 (despite giving an alternative). You may want to use threadlocker or even glue if you get the threaded balls. – Chris H Jul 16 '18 at 08:23
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Silver-brazing is strong and very doable with a propane torch.

You'll get best results (easiest brazing and strong joint) with high-silver content brazing wire. If you can grind a small flat on the bearing ball that will make it work much better; getting a concave surface in the end of the rod is much harder, even if you have a lathe available, which I assume you don't. Carefully pressing it against the side of a bench grinding wheel will work fine if your hand is steady; only grinding will work on the hardened steel bearing ball.

You'll need silver-brazing wire like this, along with the brazing flux and a propane torch:

enter image description here

If you're going to buy a new propane torch, I recommend the Bernzomatic TS8000 which is high-heat and rugged: https://www.amazon.com/Bernzomatic-TS8000-Intensity-Trigger-Start/dp/B0019CQL60/ref=sr_1_1?s=hi&ie=UTF8&qid=1531620201&sr=1-1&keywords=bernzomatic+ts8000&dpID=31N7a0ztQML&preST=_SY300_QL70_&dpSrc=srch

But most of us have one hanging around somewhere and whatever you can lay hands on should get the job done at this scale.

Silver brazing is sometimes known as silver-soldering. Actual silver soldering takes place at a much lower temperature and isn't as strong.

YouTube has many videos on silver brazing, often associated with jewelry-making. This guy does a nice job of running you through the basics: https://www.youtube.com/watch?v=D_UjkGvht_4

scanny
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  • Unfortunately this is in the family of welding, and it's not something I'll be able to use. –  Jul 15 '18 at 05:47
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    @WebHead I think fred_dot_u has the right idea, which is "get someone else to do the drilling for you". I think you'd be wasting your time with any adhesive if the item needs any strength at all. A situation like this (without a hole for mechanical strength) has the ball stressed in "peel" mode, which is the very weakest for an adhesive. If the ball just has to sit there and look pretty, some epoxy might get it done with the right preparation. But if it is part of an arm or something that has to move, I think you'd be looking at early failure of the joint. – scanny Jul 15 '18 at 18:51
  • Yes, I'm hoping I may be able to find some pre-drilled, but I feel like I may be looking under the wrong search terms to source them properly. –  Jul 16 '18 at 20:28
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I have successfully glued balls to the tips of screws in the past using epoxy. The first step is the hardest: drill out the tip of the screw to form a cup that will locate the ball (in all but one case I've been able to get this done on a lathe). Then make sure everything is completely clean and grease-free, and use a slow-setting epoxy (even better one that requires heat to cure, but that's more for industrial use). Allow to cure with the ball sitting in the screw undr its own weight. This works with quite a range of materials; in one case the balls were synthetic ruby and the screws brass.

I've generally done this using balls up to the diameter of the screw, or only a little larger.

Chris H
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  • This is mainly posted in case the "buy drilled balls" answer isn't suitable -- if you want the balls to be much bigger than the screws, that's the way to go. – Chris H Jul 16 '18 at 08:22
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Drill a small hole in both pieces, get a small piece of thick wire, number 9 worked for me, and some jb weld. I was bored at work one day and made a statue of my buddy with scrap metal and used ball bearings as his biceps. 10 years later it's still in 1 piece.

Clay
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  • I do not have tools to drill a hole in the bearing, and have not found pre-drilled balls of the right diameter for purchase. –  Sep 24 '18 at 14:01