I recently showed a tool designed for turning small balls. It is explained here :
This tool is especially useful for turning ball posts, which are the small pivots used to support the rod of a key on a woodwind musical instrument.
Here is a batch of nickel silver ball post blanks : (they are quite small, the ball is 4.5 mm in diameter.)
For supporting the rod, which is actually a long 2mm diameter screw, one ball must be drilled through, 2mm diameter, and the other ball must be tapped M2, so drilled 1.5mm.
It is quite challenging drilling such small holes through a ball shaped piece, and it is quite critical to keep well centered.
So I imagined this little fixture for that purpose, which turns out to be very effective.
Here are all the parts:
- a main body (out of hex stock)
- Two small screws, center drilled, and with a conical tip. They will act as drilling bushings to guide the drill bit.
- A tapped transversal support, that will hold the ball post while being drilled.
Here you can see how the ball post is hold in place inside the fixture.
The two screws will guide the drill bit. One is center drilled at 2mm, and the other at 1.5 mm, so the same fixture can be used for the two different sizes required, you just have to revert it upside down.
Everything assembled, ready for drilling.
one drop of oil
And here we go
What we obtain :
Perfectly true :
I can show here an example of what the finished key looks like (on my last instrument) :
Last edited by Christophe Mineau; 05-04-2018 at 04:04 PM.
I had a somewhat similar problem. In my case, I needed to drill two orthogonal holes through 1/8" diameter brass balls used as part of miniature universals. The jig and procedure is described here...
Drilling larger holes in larger spheres involves a different approach...
Home Shop Freeware
Christophe Mineau (12-28-2018)
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