Drill Bit that creates enlarged space?

[TheCreator]

I would really appreciate if someone could name something similar to what I need.

A drill bit that expands to create a spherical space at the end of the drill hole (still within the drilled material).
Or perhaps a head that can tilt sideways to slowly make an expansive area at the end of the drill hole.

My intention is to drill Quartz (prone to shattering), Pyrex, or glass.

 

[tbuelna]

With quartz or glass the only thing I can think of looking at would be to drill the hole and then use a CBN/diamond plated form tool and CNC jig grinder to (carefully) open up the spherical cavity at the bottom of the hole.

 

[TheCreator]

I was considering making a lopsided drill bit, which is similar. I have some small diamonds handy.

 

[IRstuff]

How spherical, and how accurate?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529

 

[TheCreator]

Quite perfect sphere. ~95% accurate I guess.
In the future I want 0.01mm accuracy. But for now I will be happy with 1.0mm accuracy, for testing purposes.

 

[1gibson]

You need a hole (say 1/4") from a normal bit, and then a smaller diameter bit with an enlarged head to make the void.