Model 16 bolt problem

[Shuz]

Here. https://www.amazon.com/s?k=9%2F64+steel+ball&ref=is_s

You can also use 3.5mm which is less than .004” of the .140” 9/64. I use a 3.5mm Silicon Nitride ball. Much harder than steel and almost indestructible.

Dave,
Where can I get one of those 3.5mm silicon nitride balls?