The bit tang has a double taper that fits in a notch inside the
Specialized Holt bit tangs could be purchased from the
This bit has one of the Holt tangs forged welded onto an Irwin
A special adapter could be purchased that allowed standard bits
to be used in a Holt brace.
Many kinds of boring and drilling tools were offered with Holt
On the left is a countersink, in the middle a metal drill bit,
and a large
English English center bit is on the right.