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      email: tony@lathes.co.uk
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      Duff Milling Machines USA

      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.

      A late-model Duff  with a Type VS-4 head. The compact Bridgeport-like "pancake" 1 h.p. 3-phase motor drove a variable-speed mechanism with speeds from 80 to 550 r.p.m. in a lathe-like backgear assembly and from 460 to 3000 r.p.m. in direct belt drive. Three rates of power feed to the quill were also provided  (0.0015", 0.003" and 0.005") working though a torque-limiting bronze-plate clutch that allowed the feed to continue until a positive stop was reached. The table was also provided with power feed via an unusually large motor driving through V-belts to a reduction gearbox with a quadrant selector arm on its front face.

      A Duff fitted with hydraulic table drive for repetitive production work

      Head used on the later turret miller with 4-inches of quill travel

      Earlier Duff with a dovetail ram head but a full-height electric motor

      The earlier miller, like the first Bridgeport (but without a rotating turret)
      used a round arm to carry the swivelling and nodding head.

      A clear view of the early version with the open-sided head carried on a round ram - with 12-inches of in and out movement - that socketed into the top of the (rather shallow) main column. The ram was restrained from turning by a square key let into its underside. This machine is carrying a 1-phase 0.75 hp motor.

      The early model was fitted with a rather short 24" x 8" table

      Early head with a micrometer stop arranged with both linier and rotary scales

      Right-hand side of the head showing the lever used to operate the rack-and-pinion driven quick-action drilling feed. Beneath the lever's boss is a large nut used to clamp the head in the end of the clevis arm and allow its angle of nod to be changed. The curved surface at the front of the clevis is engraved to show the number of degrees through which the head has been nodded.

      Unfortunately the worm-and-wheel driven fine-feed for the quill travel control lacked a micrometer collar

      The head was able to be twisted on the end of the round ram - the latter being restrained from turning by a square key that engaged in a slot machined along its underside.

      The round ram stopped from rotating by a square key

      Maker's plate from an early machine showing what may well be the fourth machine made - it being common amongst many manufacturers for production numbers to start with 1001

      Flange-mount motor with a simple slotted mounting bracket to release the belt tension to allow changes of speed.

      A rather fine, bevelled-faced satin-chrome plated micrometer dial

      email: tony@lathes.co.uk
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      Duff Milling Machines USA
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