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