Ahem! Coughs politely. Now then, gentlemen…
I do like that worm-drive tool – gives accuracy and good looks!
If a lever-action ball-turner produces eggs and acorns when not centred accurately, might that be an advantage in some work, by appropriate setting?
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(There is, by the way, a method for milling ball-ends, using a boring-head or fly-cutter and rotating the work on a rotary-table or dividing-head with its axis suitably inclined on a plane parallel to the machine table; but I don't know the necessary geometry for the required diameter and angular extent.)