Based at 31 Wingate Street, Haverhill, Massachusetts the Duff Machinery Company made a range of Bridgeport-like millers including the two shown on these pages: an early version with the open-sided vertical head carried on a round bar that socketed into the top of the (rather shallow) main column and a later, more highly-developed model, the 30J that, whist it used the same table, knee (and an almost identical head) was fitted with a rotating turret. A variable-speed head, the VS-4 was also offered, though whether the model number changed as a result is not clear. Although the manufacturing dates for the earlier machine are unknown the standard 30J was produced during the 1950s and arranged along well-established turret-miller lines with a simple, 6-speed V-belt drive from a flange-mounted motor carried in a simple sliding holder to adjust the tension of the V-belt. Hardened and ground, the spindle ran in precision, pre-loaded, adjustable ball bearings with the speed range spanning a useful 310 to 3400 rpm. The Meehanite cast-iron quill was 3" in diameter, lapped to a close fit in the casting and had its 4" of travel (3.5" on the earlier version) under the control of both an un-graduated fine-feed handwheel (using worm-and-wheel gearing) and a lever operated quick-action rack-and-pinion drive for drilling; a combined vertical ruler and micrometer stop, graduated in increments of 0.001", was a standard fitting.
Machined to accepted standard D-5 collets with a maximum through capacity of 5/8", the spindle of the 30J was an improvement on the earlier model, this being somewhat constrained in its metal-removal ambitions by the use of a lighter-duty, No. 2-Morse taper nose.
As movements of the sliding, swivelling, rotating and nodding head - and the 14" of ram travel - were all controlled by hand, how the operator must have longed for the features of a Bridgeport, with its easy, time-saving, safe and accurate gear-driven mechanisms.
On later versions of the Duff, the table was offered in one size only of 32" x 9" and carried three T slots to accept standard 5/8" T-bolts. The table, like the knee-saddle way, was fitted with a taper-gib strip and had 21" of longitudinal moment, a generous 9" of cross feed and 14" of vertical travel. The maximum distance from the spindle nose to the table surface was 15". Both 5 t.p.i. table feed screws were fitted with thrust ball bearings against their end brackets and had large, 3.5"-diameter micrometer dials with the engravings carried on unusually-wide bevelled-faces. Not as well specified, the earlier machine made do with a smaller table of 24" x 8"; however, although this had a longitudinal travel that was significantly shorter at just 12", the 8 inches' of in and out travel, and 12'' of up and down, were not greatly different..
Somewhat smaller and less massively-built than a Bridgeport, the Duff was not intended to compete in the same market segment and, as a consequence, with its lighter weight (some 1600 lbs in its heaviest variable-speed head form) and compact dimensions, it makes an ideal machine to manoeuvre into today's home or semi-professional workshop.