Gunner Asch fired this volley in
:

simple "Tap Busters" or "tap burners" can be had fairly regularly at
auctions and ebay for little money.

Exactly, and although F.George's suggestion would be good for someone who
had time to build and fiddle, my time is worth a lot more than a surplus
small machine would cost.

Heck... I cobbled up a crude EDM in the early 1970s that used a 250W
incandescent lamp as a ballast. It worked shrug.

But still... the features you can get for a few hundred bucks on an old
commercial tabletop machine would be fine for just teasing out the odd
tap or drill bit chips.

Lloyd