Aza Arnold was born on October 4, 1788 in Smithfield, Rhode Island, United States, the son of Benjamin and Isabel (Greene). Arnold and a descendant of Thomas Arnold, who with his family joined the English colonists in 1635 and settled in Providence in 1661.
Arnold's mother died when he was two years old and after his father's second marriage young Arnold was left to shift more or less for himself.
He attended the village school, but began working as soon as he was able, first learning the carpenter's trade and then the machinist's.
At the age of twenty he entered the employ of Samuel Slater in his wool and cotton machinery manufacturing plant in Pawtucket, but left after a few years to engage in the manufacture of woolen blankets. This venture proving unsuccessful, he next became associated with Larned Pitcher and P. Hovey in the operation of a machine shop in Pawtucket. Here he remained until 1819. In this year he moved with his family to Great Falls, New Hampshire, where he built and operated a cotton-mill.
Within a few years he was again back in Rhode Island, this time in North Providence, where he established a machine of his own for the manufacture of textile machinery. While with Pitcher and Hovey in Pawtucket he devised a machine for separating wool, in carding, into slivers so that it could be spun from the cards. It was a form of "endless" roving, roving previously having been in short rolls which had to be pieced together.
Whether the device was patented is not known, but on January 21, 1823, Arnold obtained a patent for a roving machine for spinning cotton in which he introduced a differential motion applied to the speeder. The result was a valuable improvement in cotton-roving machines, increasing both quantity and quality of product. It was introduced into England in 1825 and was characterized as being one of the most important machines for spinning cotton.
While some American manufacturers acknowledged this invention and paid Arnold royalties, others, especially those outside of Rhode Island, refused to do so, and, in the course of the infringement suits which Arnold brought, the whole code of patent laws was repealed and the new code of 1836 was passed, but Arnold received no redress for the infringements.
In 1838 he gave up his machine shop and moved with his family to Philadelphia, where he operated the Mulhausen Print Works. Here he remained for about twelve years, when he went to Washington, D. C. , established himself as a patent attorney, and continued in this capacity until his death.
Arnold's last known invention was a "self-setting and self-raking saw for sawing machines, " for which patent No. 15, 163 was granted him on June 24, 1856.
While it is said that he invented a machine for cutting files about 1812, no record of this invention is to be found in the Patent Office.
Arnold married Abigail Dennis of Newport, Rhode Island, on July 28, 1815. They had seven children.
