Manufactured by Vernon Machinery Manufacturing Company of 1915 East 515T Street, Vernon, Los Angeles, California (and originally sold under that company's "Vernon" label) Sheldon marketed both vertical and horizontal milling machines. The vertical miller (details can be found on the Vernon pages) was really a miniature jig borer along the lines of the well-known Linley while the horizontal model, shoen on this page, was of utterly conventional design and construction but with the advantages of variable-speed drive and an epicyclic backgear built into the V-belt drive pulley to give a range of especially slow speeds.
The spindle, of heat-treated, ground-finish steel was bored through 9/16", had a No. 9 B & S taper, ran in taper-roller bearings and was supported by a round overarm. The drive system was completely enclosed within the cast-iron cabinet base and consisted of a 1 hp single (or 3-phase) motor which drove a robustly constructed, double-acting expanding-and-contracting (wide V-belt) variable-speed drive unit with ordinary twin V belts providing the final stage of the drive to the spindle; the variable-speed control handle was mounted in a rather inconvenient position on the left-hand cabinet face. The motor was fitted, as standard, with a two-step pulley, so offering both high and low speed belt-drive ranges (Model 3000P) whilst as an option the customer could specify an even slower set of speeds by choosing the epicyclic speed-reduction-gearbox equipped Model 3000PQ - a feature inaccurately described by Sheldon as a "Backgear"; the arrangement is illustrated at the bottom of this page. The quoted speeds varied during the years of production: in its model 3000PQ form the speed range in 1947 spanned 17 rpm in "backgear" (when combined with the belt-driven low speed) to as high as 1002 rpm in direct-drive on the high-speed belt setting. By the mid 1950s the direct-drive low-speed pulley was giving 125 rpm to 550 rpm and the high-speed direct-drive 225 rpm to 1100 rpm; in "backgear" the low-speed pulley provided 25 rpm to 100 rpm and the high-speed pulley 36 to 198 rpm. By the 1960s, when the miller was mounted on an entirely different design of sheet-metal cabinet stand - with a tachometer built into its front face - the speeds became 20 rpm to 250 rpm in "backgear" low-range and 75 rpm to 1400 rpm in high-speed direct drive.
Originally the table was 20 inches long and carried just a single, 7/16" wide centrally-positioned T slot; later models had a slightly longer, 22-inch table (but of the same 5.25-inch width) with 3 T slots. The longitudinal travel was 12 inches when operated by the screw feed (but 10 inches when moved by the optional, lever-operated rack) and the cross travel, generous for a small miller, a useful 5.5 inches; the vertical travel of the knee 9.25 inches. The table was offered with a simple power-feed attachment driven from a 3-step pulley on the rear of the main spindle; it drove through a universally-joined and splined shaft with engagement by a drop-out worm and produced four feed rates of 0.008", 0.0016", 0.0032" and 0.0064" per revolution on the 3000PQ model - and 0.003", 0.005" and 0.008" on the 3000P.
At least type types of vertical head were offered for the miller - one a simple "plug-in" type that socketed into the hole used for the round overarm (and driven from the horizontal spindle) and the other a self-contained motorised unit which fitted onto the end of the overarm and enjoyed the advantage of a quick-action quill feed and the facility of being able to swivel through 180 degrees.
Photographs of a Vernon-badged Sheldon horizontal miller can be seen here..