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Scientific instrument maker, who produced improved dividing engines
1809 'Divider of mathematical instruments' at 12 Blewit's Buildings, Fetter Lane, London
1816 Allan published a description of his method of making screws of an accuracy which he claimed was suitable for application to scientific instruments, using a relatively simple machine. In this the workpiece was located in bearings, but free to move axially, and was pressed against a curved, inclined cutter. After cutting a shallow groove with one turn of the workpiece, a follower was pressed into engagement on the opposite side to the cutter, in order to guide the workpiece for cutting the remainder of the length. The depth was progressively increased, before changing the cutter for one suitable for cutting the finished depth (the first cutter having a radius suited to the outside diameter). Allan advocated turning the workpiece round and running it through again to ensure the the angle of each flank was symmetrical. Different pitches were obtained by altering the angle of the tool.. Note that the method has some similarities to that used c.1800 by Henry Maudslay to produce master screws in a special jig in which a curved 'chisel' was pressed into the workpiece at a precisely-defined angle.
1816 The Society for the Encouragement of Arts, Manufacturers and Commerce awarded 'James Allen' the Isis Silver Medal for his Method of making screws for mathematical purposes.
1820 Advert: THE BOARD OF LONGITUDE. THE Honourable the Commissioners of the Board of Longitude, after an Experimental Examination of the comparative Merits of the different Engines used for the division of Sextants, Quadrants, Theodolites, &c. came to a Resolution on the 3d. of February, 1820, acknowledging the superior Accuracy of the SELF-CORRECTING DIVIDING ENGINE, invented by J. ALLAN, No. 12, Blewitt’s-buildings. Fetter-lane; and, in testimony of their approbation, conferred upon him a Reward of One Hundred Pounds.
J. ALLAN has also been honoured with the following Rewards by the Society of Arts, viz.:— In May, 1810, a Gold Medal, for his Self-Correcting Dividing Engine; in May, 1811, a Silver Medal, and Twenty Guineas, for his Improved Reflecting Repeating Circle; and in May, 1815, a Gold Medal, for his Improved Theodolite, and a Silver Medal, for his Improved Method of making Screws for Mathematical Purposes.
N. B. Sextants sold, warranted good, wholesale and retail.'
1821 'Died at Drumduan by Forres (at 2 o'clock A.M.) on Friday the 7th instant, (and was buried in the Church yard of Forres, on Sabbath the 19th current) Mr.JAMES ALLAN, late Mathematical Instrument Maker (at 12, Blewitt's Building's. Fetter-lane) London. He was a native of Forres, where he learned, and for some time followed, the trade of blacksmith, in which his success was not remarkable. But having afterwards gone to London to prosecute his trade, and there boarded in the house of a Sextant maker, whom he assisted in the evenings after the usual work hours, he soon distinguished himself as an ingenious workman, and became so successful in the making and dividing Sextants to bring the work of that Artist into high repute. From this period he changed his profession of blacksmith for that of Mathematical Instrument Maker, in which he afterwards distinguished himself several important improvements in the construction and division of the Sextant, the reflecting Circle, and the Theodolite, besides a highly improved method of making Screws for mathematical purposes, for which had the honour to receive in succession several gold and silver medals and pecuniary rewards, from the London Society of Arts.'