Drill a 100% Centre in a Ball Bearing

When I had to drill into a steel ball, I mounted it in a collet on my lathe, also using a collet stop to give the ball an additional "backstop". I then machined a small flat spot on the face, at a diameter slightly smaller than the hole I wanted to drill. This was to keep the center drill from walking around on the curved surface. After center drilling, I proceed to drill the desired diameter for the through hole.

Hope this helps.
 
Simply that drilling a hole in the center of a spinning part tends to center the hole on the axis of rotation, as we commonly do on a lathe. Note that I did add that the hole would then need to be bored for an accurately centered hole. I also noted that the ball needed to be spinning true with the center of rotation, and that a flat spot on the ball was needed to get a straight start. Is there an error with my thinking?
Not at all, however it is not the spinning part that helps center, it is the tool which is free to move when drilling in a lathe, one would hope that a part held firmly in a lathe spindle is not free to move about if you know what I mean.
If both tool and part are held rigidly which one rotates is unimportant all other conditions being equal.

If doing such a job I would never use a center drill to start but a spotting drill, then a center if a 60 Deg. shape is required, center drills are not required to have accurate diameters only accurate angles, they are for making centers not drilling or starting holes.
 
My thoughts.

Find a collet you can put a depth stop in. Put the ball bearing in the collet in your lathe. Use an end mill to cut a tiny flat. Then center drill or a spotting drill, then drill. Use a stub length screw machine drill. If its a good hard bearing it might still not work.

Even a big heavy center drill will walk a little on a spherical surface. I do something like that to drill the side hole in high pressure injection probes.

A cheap and cheesy edge finder is a fairly tight bearing assembly pressed on the end of a shaft. Its not super accurate, but its something anybody can make.
 
If you want the hole in the center of the ball, you will need to be spinning the ball, not the drill. The ball will need to be centered ...

Consider an EDM plunge tool (the cheapest kind of EDM tooling) onto a rotating
hardened ball. If the rotation axis is not aligned to the plunge axis, this makes a tapered hole. It's
relatively easy to press a stem into such a hole. Heck, if you want to get fancy, you can
do this to a tungsten carbide ball... or boron carbide. If your tool is cylindrical, and at
least half the diameter of the entry, it makes a clean frustum-of-a-cone cut.

The ball DOES have to be spun on its axis, which ought not be hard to arrange. Harder,
is keeping the ball elecrically connected so your rotary holder mechanism doesn't get sparked.
 
Not at all, however it is not the spinning part that helps center, it is the tool which is free to move when drilling in a lathe, one would hope that a part held firmly in a lathe spindle is not free to move about if you know what I mean.
If both tool and part are held rigidly which one rotates is unimportant all other conditions being equal.

If doing such a job I would never use a center drill to start but a spotting drill, then a center if a 60 Deg. shape is required, center drills are not required to have accurate diameters only accurate angles, they are for making centers not drilling or starting holes.
All good comments, Wreck. I also agree with the advice on not using a center drill for starting drilling operations.
 
Thank you very much for all the replies. What I would give to have your experience. The reason I opted to make a Wiggler is because I were not able to find a Center Finder either. I tried to "convert" my Edge Finder to a Center Finder. We are not so Geared for the Hobby Machinist here in SA (I would like to hear form other members form South Africa where they get there tools). You can find the items on ebay or even suppliers themselves on the net, but most of the times the postage is more expensive than the actual item. I am really indebted to people like you, because if I have a problem, I know where I will get help. Thank you again.
 
You can get the UK cromwell/Kennedy tools in SA. I usually order from SATOOL. (other than a customer I have no association with them. ) They have quite a comprehensive catalogue . I just phoned them and they can supply a 5 piece wiggler set for R 200.00 approx.

hope this helps

charles
 
You can get the UK cromwell/Kennedy tools in SA. I usually order from SATOOL. (other than a customer I have no association with them. ) They have quite a comprehensive catalogue . I just phoned them and they can supply a 5 piece wiggler set for R 200.00 approx.

hope this helps

charles
THANK YOU VERY MUCH CHARLES! Does SaTool have a website, or can you order form them out of the Cromwell Catalogue?
 
You can just quote the Cromwell tool catalogue number, phone them quote the part number, from the catalogue . They are online to the main indent agent, so if it is not in stock with them they can get it from the agent. In your case the agent had 27 in stock , when I asked. Hope you come right

cheers charles
 
I think his problem starts with the ball getting the flat spot and hole started straight correct. When making the wiggler he should have made the ball and rod one piece . I'd use a ground tool to turn the ball and point out of drill rod then there's no problem centering .
 
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