Smallest possible hole through a 2" ball bearing? How?

Bill Kahn

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I am making a variation on Newton's Cradle--you know, where the steel balls bounce against each other. But for my purpose the steel balls need to slide up a line (string/thread/cable). The coefficient of restitution is important in my application so I want to use very hard steel. Ball bearings probably. The largest will be 2" diameter.

I need to drill a hole through a diameter of the ball bearing. I guess I could buy some expensive carbide drill, say 1/2" diameter and make it through the bearing. But I would much rather use a much thinner guide line. Ideally even I would like to use .01" fishing line. But .05" wire would be ok too.

I have no idea how to drill a .01" hole through 2" of hard steel. I think that I start with a 01" .2" long carbide bit and then, with .2" supported go to a .4" long bit. Then a 1" and then a 2". Are such bits made? Would that sequence work?

Or, is there a water jet technology? James Bond like lasers? Or some totally other way to get a tiny hole through 2" of hard steel.

If I can't get a .01" hole, what can I get? How small can the 2" hole be? How?

Thank you for any advice.

-Bill
45 years ago loved high school shop. And finally getting back to it.
 
I am making a variation on Newton's Cradle--you know, where the steel balls bounce against each other. But for my purpose the steel balls need to slide up a line (string/thread/cable). The coefficient of restitution is important in my application so I want to use very hard steel. Ball bearings probably. The largest will be 2" diameter.

I need to drill a hole through a diameter of the ball bearing. I guess I could buy some expensive carbide drill, say 1/2" diameter and make it through the bearing. But I would much rather use a much thinner guide line. Ideally even I would like to use .01" fishing line. But .05" wire would be ok too.

I have no idea how to drill a .01" hole through 2" of hard steel. I think that I start with a 01" .2" long carbide bit and then, with .2" supported go to a .4" long bit. Then a 1" and then a 2". Are such bits made? Would that sequence work?

Or, is there a water jet technology? James Bond like lasers? Or some totally other way to get a tiny hole through 2" of hard steel.

If I can't get a .01" hole, what can I get? How small can the 2" hole be? How?

Thank you for any advice.

-Bill
45 years ago loved high school shop. And finally getting back to it.

Bill, you need to look for a harder project!

Seriously, you have picked a formidable task. Drilling a .01" hole through 2" of steel would be hard enough but through a hardened ball bearing? Wow!

A water jet may be able to do the task although it is a fairly deep hole. It might be possible with a laser as well. My gut feeling is that you wouldn't get a clean hole that deep. EDM would have to be done with carbon electrodes and a carbon rod .01" in diameter and 2" long would be rather flimsy.

A thought would be to make a larger diameter hole and insert a bushing with the desired i.d. The hole could be drilled or EDM'd. Once a pilot hole was made, wire EDM or a laser could give you a clean hole.
 
EDM (i.e. judicious use of lightning) can drill hard material, as can grinding (ultrasound pecker and abrasive
grit). Neither is very fast or suitable for deep/narrow holes. Could you create the ball from unhardened material,
drill that, and re-harden it?
Or, could you use a glass bead? Those are formed on a bit of wire, and (by stretching the wire)
you get a nice hole, without all the distress of machining it. Restitution is good (glass rings like a bell).
 
.010 drills are really tiny. I routinely drill .036 holes through 3/16 aluminum, generally get about 6 good holes per drill. They break easily. And, finding good, well sharpened .036 drills is a challenge. I bought 20 once, found 6 that would cut aluminum. The others were improperly ground. .010 is really tiny. No. 80, the smallest commercially available is .0135.
 
Bill I know two tool and die makers, and they verified my first impression. In a fully equipped manual tool and die shop there's no way a professional T&D would take the job. Your only hope is laser drilling (about 80$ per hole) or fast die sinking EDM (at about $100 per hole). These prices are from jobs I have personally had done in the past (not in ball bearings, however) Because the surface is not perpendicular, the waterjet shop I use wouldn't touch it either because the hole won't sink properly...
 
For an EDM drill, neither graphite nor copper are suitable (long, thin, floppy copper or
high-electric-resistance graphite), but a less-durable tool can be fashioned from the small SS tubing
such as hypodermics use. 22 gage (about 0.028" diameter) to 27 gage
(about 0.016" diameter), with some kerosene flow through the central hole to cool and flush
the cut, would make holes under 0.040". Slowly. With lots of tool wear (and replacing the
cutting tube means some alignment fiddling).

Spinal needles up to seven inches long are of such tubing.
 
I am making a variation on Newton's Cradle--you know, where the steel balls bounce against each other. But for my purpose the steel balls need to slide up a line (string/thread/cable). The coefficient of restitution is important in my application so I want to use very hard steel. Ball bearings probably. The largest will be 2" diameter.

I need to drill a hole through a diameter of the ball bearing. I guess I could buy some expensive carbide drill, say 1/2" diameter and make it through the bearing. But I would much rather use a much thinner guide line. Ideally even I would like to use .01" fishing line. But .05" wire would be ok too.

I have no idea how to drill a .01" hole through 2" of hard steel. I think that I start with a 01" .2" long carbide bit and then, with .2" supported go to a .4" long bit. Then a 1" and then a 2". Are such bits made? Would that sequence work?

Or, is there a water jet technology? James Bond like lasers? Or some totally other way to get a tiny hole through 2" of hard steel.

If I can't get a .01" hole, what can I get? How small can the 2" hole be? How?

Thank you for any advice.

-Bill
45 years ago loved high school shop. And finally getting back to it.


Wow. Thank you everyone. Now isn't this a case of out of the "mouths of babes..." I would have thought drilling a hole (albeit small) through a metal ball (albeit hard) would not have been well near impossible. But, so be it. While it may well be possible to have some professional make it for some price, I am enjoying making stuff myself. Like for all hobbyists, it is the journey. I have many other ideas of simple projects that have caught my eye. While help in getting going on a project is always wonderful, knowing I have bitten off too much is even more so. Thanks again. Best, -Bill
 
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