Sold as the "Duro" only during 1942 (the year of its introduction), but made until the 1950s as the "Benchmaster", the Duro milling machine was made by the Duro Manufacturing Company at 800 East Sixty-First Street, Los Angles in California. A 1943 reference in Electro-technology (Volume 32, page 248) reports that: Duro Mfg. Co., Los Angeles, Calif., makers of bench-type machine tools, changes its name to Benchmaster Mfg. Co., effective immediately. The firm's main business appears to have centred around punch presses and their most popular earlier miller (or at least, the one that appears to have survived in greater numbers than any other type) was a simple, lightly-built affair, designed (naturally enough) for bench mounting. Available with hand feeds only - and obviously intended for the amateur market, or perhaps for an automotive workshop ambitious enough to attempt some basic machining - it stood 24" high on a (rather thin) 8" x 12" base and weighed 185 pounds. The top of the simple, cast-iron, "I" section main column was bored through to accept a solid steel bar on the front of which was the milling head with, at the back, a motor on a plate hinged to work in the vertical plane - a most unusual arrangement but one that certainly facilitated quick changes of speed. Drive was by a V-belt, running over 4-step pulleys, to a precision-ground spindle running in taper roller bearings and fitted with a No. 2 Morse Taper nose. Spindle speeds, from the usual 1725 rpm electric motor were: 450, 850, 1400 and 2100 r.p.m. - an entirely adequate range for its intended purpose.
A serious omission on such a small machine intended for fine work was the omission of a quill feed on the head, any up and down movement of the cutter having to be made by raising and lowering the knee using a screw feed - though as this was fitted with a crank-handle, rather than a full-circle wheel, control of very fine feeds would have awkward. The head of the miller was graduated and could be inclined sixty degrees each side of centre - as well as moved in and out to a small extent.
While two (or even just one) T-slots might have been expected in the table of so small and inexpensive a machine, the Duro had three, each 3/8" wide on 2-inch centres. A just-adequate 6" x 14", the semi-steel table had a longitudinal travel of 8", a traverse of 5" and a vertical of 8". All the table and knee screws were fitted with crank-handles of the "turn-free" type (which engaged on splines) and were fitted with direct reading, 0.001" graduated micrometer dials. Although the "gib blocks" fitted on knee and saddle to adjust free play in the slides provided some increased rigidity, they were annoying time-consuming and difficult to set correctly. Only the smallest adjustment of the push screws was possible if the assembly was not to lock solid as the securing bolts were done up.
Later models, branded Benchmaster, were significantly improved and included the option of a power-feed table (that attached with just two bolts) and complete guarding of the belt run.
If any reader has a Duro miller, or any company literature, the writer would be interested to hear from you.