Inventors in the 19th Century
sought patents for improvements to tools to make them perform
better and sometimes, with more precision.
Such is the case of G. L. Holt of Springfield, Mass. who on June
29, 1875, was granted U.S. Patent No. 164,999 for a more
precision way to hold bits in a brace.
The Barber Shell Chuck, patented a decade
earlier, had seized a big part of the market and was quickly
making button and lever chucks obsolete. Holt took the idea of a
shell chuck and promoted it to a higher level. He promoted the
concept that a bit which could be screwed into a brace chuck
would eliminate wobble in boring. His patent called for a
threaded brace tang that screwed into a brace chuck, but the
patent drawing did not illustrate a brace.
I found such a brace in 1963 with one bit, and since then I have
aggressively attempted to build a set of bits to accompany the
brace. The bits you see in the first photo were added to my
collection one at a time. I will never find one each of all the
tools that accompanied a Holt brace, but I have successfully
assembled what is probably the most complete set known to date.
The bit tangs have left-hand threads and a double taper on top
of the tangs.
A shell chuck on the brace is rotated left, and inner threads
draw a bit into it and the taper on the tang seats in a vee
notch in the brace frame. This retains a bit on the precise
longitudinal axis of the brace, and the tang in the notch
prevents the bit from slipping in the chuck.
I use this brace, and itís bits on occasion when
I do some very precision boring. It performs exactly as the
inventor envisioned. If you find one of these Holt braces at a
yard sale, you can sell it for a handsome profit to an advanced
My Holt brace and all the auger bits for it I have been able to
The shell chuck has left hand internal threads that draws
the threaded bit into place.