taking one frame at a time since 1999

'soft' steel balls... good idea? + silver solder question

Hello everyone,

Just a quick question about ball bearings... I came across these ball bearings which say they are 'machinable' and low carbon...

I was wondering if it would be a good idea to buy those or not... I have so far used stainless steel 302 steel balls, as I found recommended here mostly as well, but still had to anneal them to make it possible to drill through them... This means they're softened anyway of course, but I don't know how comparable that would be the ones offered here... It says they're 'soft polish AISI 1018 Carbon Steel'. Say, I'm using ordinary mild steel for the joint plates, would these softer steel balls still be hard enough to work well as a bearing?

I noticed with other steel balls I used which were annealed by someone else, that they may have gone too soft, as of some even the surface seemed to be affected and showing some irregularities... The ones that I tried annealing myself were still quite hard but possible to drill through with some patience...

I'm very new to ball and socket armature making and have just been diving into it since the last couple of months. I might open another thread for more of what I'm working on, but here's a link to a little test of what I've achieved so far:

* edit: just adding a question about silver solder... Which so far I've been buying at a store at my university (I need to check the exact brand/name of the stuff sold there again), but it seems it is turning out pretty expensive (14p per cm) (I'm going through it quickly sometimes, due to learning and needing practice, making mistakes, etc.). I found some online suppliers where it seems a lot cheaper, but I don't know what to consider exactly for good quality. I know it has to be high silver content, so about 55%? I read about a brand name in another topic, but it seems to me that it is a US brand as I couldn't find it easily to buy from UK suppliers (I'm in the UK). Is there anyone out there with good advice on UK suppliers for silver solder? I found something 55% called 'Fontargen A 313', about 20 pounds for 5 meters... does this say anything to anyone here?

Thanks for the time reading this as always, appreciating any help. :)


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Hi Roos - I don't really know much abut metals, but I *think* 1018 carbon steel is a lot harder than 302 stainless. Hopefully if I'm wrong somebody will correct me. 

I'm surprised you had to anneal 302 - how are you drilling it? Do you have a drill press and a good vise? Any kind of jig to hold the ball for drilling? And have you tried filing off a flat spot on top before drilling? That one made all the difference for me. When it was still round on top the drill bit just kept walking off the edges, but once I filed it flat suddenly no problem. It also helps to use short 'jobber' drill bits, they flex less than the longer standard drill bits, and of course if you spend a little extra to get coated bits or ones made of carbide they work even better. 

You made that wing?!! I saw it when it showed up on YouTube a few days ago, but I assumed it was made by the guy who's making the Harpya film (sorry, can't remember his name just now). Wow, that is amazing work, both the armature work and the animation on it!! You're making major advances here! 

Thanks for the reply strider!

Hmm, after doing a bit more research myself it seems like 1018 low carbon steel IS mild steel. I don't think it will be harder then 302 stainless steel... I bought the 302 ss steel balls from this same supplier. So you can drill them without annealing...?

I am using a pillar drill (at my course) and vice and made a jig to hold the balls.
I've kept (read, updated everything at once some weeks ago, then tried to keep updating) a blog on the process. Was going to share it here soon anyway, but here is the post where I made the jig:

I didn't file a flat bit of, but the balls are clamped and the drill bit centered, leaded by a centered hole, which worked fine with the annealed balls. When I tried drilling a not annealed ball I had no problems with the drill bit walking off, but after a long time drilling came no further then a tiny dent in the ball... I tried using titanium coated drill bits. Was just checking all the drill bits I bought and was just getting really confused, but yes, I think I had three titanium coated for the size I used most but broke them all three along the way, so for last balls I drilled (annealed ones) I used an ordinary drill bit, which worked ok. Hmm, so I am not sure what I am doing wrong not being able to drill through the not annaeled ones? And I'm not sure still now if I should get those softer ones. Perhaps I should just get some more ss 302's and anneal them again as it seemed to work ok for me, and the ones I annealed are still having a smooth surface and are still pretty hard...

Yes I made that wing. :) Thank you for the compliment. (The guy from the Harpya film is Daniel Svensson. The body of his bird is ball and socket but the wing mainly wire for what I can see and what he told me.) I thought I should better make use of the metal centre at the university I'm now, while I can, so decided to try and learn ball and socket armature making. :) It's a huge learning curve. On my blog you can read all the billion mistakes I made along the way.

Just finished the second wing today, with a new design again which I'm finally happy with (this wing will be adapted, to make the same changes). ;) Only not happy with the smoothness of some of the bigger steel balls...

You should not have to anneal 302 (or even 304) stainless.Check your RPM's and the drill tip to be sure is isn't dull/damaged.I do not reccomend annealing hardened ball bearings.You stand the great possibility of damaging them. You need to either machine or file a small flat on the ball bearing,spot drill,then drill your hole.Its usually best to "step drill",meaning if you are drilling a 1/8 inch hole into a bearing (after spot drilling w/a #1 spot/center drill),start with a smaller drill,like 1/16 and you can step up to a larger "in between" sized drill before finishing with the "final hole size".It also isn't recomended to use ball bearings thast aare softer than your ball bearing sandwich plates.As I recall,Tom wrote in his book that the rule of thumb is to use material such as 302(or 304) stainless ball bearings and the plate material should be "softer" than the bearings.Either aluminum,brass,low carbon steel etc.The joint will wear out and break down quickly if you use soft ball bearings.

Thank you very much for the reply. Ok, that is helpful... though a bit confusing now as well having read and heard so many different things. I would imagine that when starting with a smaller drill bit it may be even more likely to break? But then, it does make sense as well... I knew that it is important to have the balls harder than the sandwich plates, but I wasn't sure on how much softer the balls would become from annealing. The ones I tried seem to be still harder then the mild steel I'm using for the sandwich plates. They don't seem to be damaged... The bigger ones clearly are though (but I am not sure what type of steel the original ones were, as I haven't bought these myself).

What RPM would you recommend for drilling them? I have been drilling on quite low speed as I found that higher speed was more likely to break the drill bits... Should I be able to drill through the ball bearings with sharp ordinary HSS drill bits, or more chance on success investing in some new coated or carbide ones? Obviously when I just got the drill bits they will have been sharp and not damaged. I used titanium coated ones before as well (until all three broke), which I bought new. The ordinary HSS drill bits I have been using for the last (annealed) balls I drilled may be getting dull by now, though they still seem to be working.

Sorry for asking so many questions, I have a lot to learn in this field...

A center drill won't break nearly as easily, because f the way they're made:

Thick right up to the very end. This will get through the hardened outer layer, and then you can switch to a regular HSS bit or a carbide or coated one. Filing a flat spot also helps to get through some of the hardened casing. With hardened balls, it's only an outer shell that's hard, inside it has a soft chewy center. I've never had to use progressively bigger drill bits after using the center drill, I just go straight from it to the actual bit I need, though I can easily see how that might be necessary for drilling larger balls.

And yes, you want to drill nice and slow, and use a lot of lubricant. If it seems like something is going wrong back the drill out - meaning stop pressing down and instead raise the drill out of the ball as it's still spinning. Sometimes a drill will 'catch' inside the hole which could break it if you just keep drilling. Or sometimes the metal chips get jammed up inside and can break a drill - it's necessary every few seconds to ease off on downward pressure and lift the drill out as it's still spinning, in order to clear the chips and spiral metal pieces that might be accumulating in there. I wear gloves when I'm drilling (as well as eye protection) so I just use my gloved fingers to sort of pinch around the drill bit and pull downward, which clears most of the chips and spiral pieces out of the flutes (Obviously turn the drill press off when doing this step). I might need to do it several times, or possibly even pick up a little paintbrush I keep there to get in and pull out any stubborn ones. 

So essentially it's a process where you take small 'bites' with the drill, just drill a little way in, then back out and clear chips, then add some more lube and do it again. You might need to repeat this process 6 or 10 times in some cases before you drill deep enough. 

I'm wondering if maybe the store gave you the wrong kind of steel? They might have sold you something harder that was mislabeled as 302? I don't know, or maybe there's some problem with your drilling process - if there's too much flex anywhere in your system that can easily break drills. I followed Trikfx's advice to raise the platform of my drill press, jam a block of wood under it, and then crank it down until it's secured hard against the block, which now acts as a strong brace to keep it from flexing. 

All of these little tricks add up until at some point you'll eliminate whatever the problem is. 

Oh, and I should add - don't push down hard on the handle of the drill press - just ease it gently down and let it slowly start to drill into the ball at it's own pace. It shouldn't take much more than the weight of your hand on it to get it going. If you push hard that will break a drill bit. So it's a very gentle little-by-little process. 

Use Cobalt drill bits. They cut into 302 SS nicely and can be purchased in most hardware stores in the US.  Dunno about the UK. I have made a lot of joints with 302 balls and 1018 plates, and some with O1 plates. Both fit the "plates must be softer than the ball" test.

Here's a jig I use to drill balls:

No need to use a centering drill or file or any of that.  The holes in the plates guide the bit in the right place and nature takes over.

Cobalt, that's what I meant - I said carbide instead. Oops! Curse my awful memory! 

Hmm.. so then 1018 steel is softer than 302.. but you'd still need a softer metal for the plates (if you use 1018 for the balls). 

Thanks for the replies again. Ok, it looks like I will have to get new ball bearings of the bigger kind I was using (I found out today that the original ones of those which I used were ss 316, still the annealed ones were too soft) and try drilling them without annealing with all the given suggestions. I will keep my annealed smaller balls, they still are harder to drill then my mild steel plates, so I assume they are still harder (I didn't know the exact annealing cycle, only could find some info on certain temperatures).

Those jigs look like something similar to what I made, only I made it only for one ball at a time and two screws at the side to tighten. I will get some new cobalt drill bits. I couldn't find them in a hardware store before, but there's always online places that sell them otherwise... And the center drill sounds good too...

I did drill in short bursts, taking out the drill bit constantly, and at low speed and with loads of cutting lubricant. It is possible that at some point when nothing was happening I started to try and push too hard. I tried not doing that at first, but maybe got too impatient in the end when nothing seemed to happen? Perhaps that was because of the hard outer shell, so maybe that will be easier with the center drill... I experimented a bit in the start to find what worked and what didn't. In the end it worked better and I didn't break many drill bits, but I can't remember exactly what and how long I tried drilling the not annealed balls. I probably had been told by too many people that I had to anneal them, which made that I didn't try for too long drilling them without.

Thanks, that was helpful! More things to re-do, re-think, solve, understand... Hopefully I can get the new balls and drill bits soon, and will post here how it went this time...

So this should definitely be the right kind... ss 302 unhardened...? This is where I got my previous ones from too. Unfortunately I can't try again with new drill bits if I can drill through them not annealed, as I recently annealed all of them when I needed more (after first tested with a few).

I can't seem to find a uk supplier, only one I found that had the ss 302 kind only sold them to companies or something...

You can machine S.S w/HSS tooling,you just have to slow your rpm's down.When drilling(with any drill bit)  "peck".That means when you move the tailstock on the lathe(or the quill lever on a drill press or vertical mill),you don't ram it in all at once.You'll bend/break the drill bit for sure.When "center drilling" ease it in in a slow,consistant,smooth,steady motion(I think someone mentioned that?).Also,your rpm's can be a bit higher,they are calculated differently for center drills.If you go too slow using a center drill,you will BREAK IT guaranteed.Cobolt is a bit tougher than HSS,your rpm's are about the same,possibly a tad higher?Just look/listen to what the tool is doing in the material whether it is S.S,low carbon steel etc.If it is squealing/smoking,making dark or blue/purple chips) you are going WAY TOO FAST.Slower is Okay,but of you go too slow the surface finish will be poor.If you happen to "have" the money and the lathe,vertical mill you are running has the rpm's,you can use carbide tooling.You can run your rpm's pretty high (I forget what they are).302 and 304 stainless is still pretty soft/machinable,but when you get into the really tough case hardened stuff,you can't machine it.It wouild be extrodinarily difficult (if not impossible) even with really expensive tooling  like carbide,industrial diamond,or ceramic tooling.Other means are required (EDM or elcorto chemical machining),and no one in here can afford that.

Another way around- I have been using 8mm threaded ball bearings and reaming them out to size.

You can use the replacement balls from piercings, which are Hard surgical steel. They aren't large though, but cheap and have a pilot hole ready.

Combined with Sriders centre drill and you should go through a lot fewer drill bits.

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