William Simms' chief interest was the division of the circle, the accuracy of which was essential to the manufacture of accurate scientific instruments.
He became a correspondent of Thomas Jones, who brought him into contact with the instrument maker Edward Troughton and also persuaded him to join the Royal Society for the encouragement of Arts, Manufactures & Commerce.
Later Simms wrote a paper for Troughton proposing a new method for dividing circles that was more accurate than an engine and quicker than using a roller.
On a larger scale he supplied telescopes, mural circles and other astronomical instruments to observatories at Kraków, Madras, Cambridge, Lucknow, Calcutta, Edinburgh, Brussels, Greenwich and other places.
His reputation was enhanced by the improvements he made to graduating instruments and his self-acting circular dividing engine reduced the work involved in manufacture from weeks to hours.