On Sun, 12 Jul 2009 21:52:09 GMT, "The Medway Handyman"
had this to say:


Tapered square? WTF is that?

It was used for many many years to hold a bit in a carpenter's brace.
It gave a positive grip, but is rarely seen nowadays - most 'bits'
seem to be SDS.
(Somewhere) I still have a 'tank cutter' with a tapered square shank,
intended to cut (pretty obviously) a hole in a metal tank, infinitely
variable from about 3/4" to 5" diameter. It has a 1/4" pilot drill
(which is probably best replaced with a plain 1/4" steel spindle
inserted into a hole made with a 'proper' drill!), and an adjustable
radial cutter.
My carpenter's brace is long defunct - ISTR that it cost 4/6d from
Woolworths about 50+ years ago - actually it was very good!
The posh 'ratchet' ones cost about 7/6d...

--
Frank Erskine