JMB Specification Sheet
Seldom encountered, the little JMB universal miller was smallest of those made in Germany by Josef Mellert / Bretten and appears to have been made during the 1950s and offered in a number of versions. Models discovered to date include the HF-3K, HF-2/56, HF-2/53, HF-V/56 and HF-V. The HF-3K, was a simple "stub-milling" machine for basic repetitive production work that lacked the facility to mount an overarm and equipped with lever feed to the table's longitudinal travel, its table being a compact 360 x 75 mm . Of greater versatility, the HF-2 had a supporting overam for conventional horizontal milling and was built in several versions including the HF-2/56 with a 500 x 135 mm table with more travel on its Z axis.Some images below are high resolution and may take time to load
Of compact dimensions, but very heavy build - though to be around 350 kg - the smaller HF-2/53 had a 500 mm x 135 mm table with a longitudinal travel of 280, in traverse of 105 mm and vertically 105 mm (specification sheet here). Although the horizontal models could be fitted with a plain (non-quill feed) vertical head driven direct from the main spindle and able to be swivelled though 90° each side of vertical, complimenting the types HF-2 - yet closely based upon them - was the HF-V, a dedicated 6-speed vertical-only model. Formed as an integral part of an enlarged overarm that clamped into the same V-ways as used by the overarms of the horizontal models, the vertical head was, unfortunately, of the simplest fixed, non-swivelling type and, even more limiting, lacked any form of quill feed. Drive to the head was direct from a motor bolted, in a vertical position, low down on the back of the main column. To reach the remote, top-mounted pulley (which ran in its own bolt-on bearing housing) the motor shaft was connected to a second shaft by a Bowex Type "Junior" semi-flexible coupling - a unit used on a variety of machine-tool and other drives. Both vertical heads are believed to have take long collets of the Schaublin 20 type. JMB also manufactured a small drill press - again, its model type has yet to be discovered.
For a small milling machine the JMB had a particularly wide main column, allowing the knee ways - and consequently those for the saddle - to be spaced well apart for added rigidity. Also of substantial proportions and unusually long, the saddle supported a good proportion of the three-T-slot table (with a coolant trough) for all but the extremes of its hand-feed-only travel.
Driven by a motor held inside the base of the column on the horizontal model and bolted to the back of the column on the vertical, either five or six spindle speeds were available with drive on the vertical direct to the spindle (giving a range estimated to have been from around 200 to 3000 r.p.m.) and, on the horizontal, in order to reduce the speeds, by a 2-stage V-belt arrangement that gave, on the 6-speed type: 100, 175, 305, 540, 700 and 1250 r.p.m. The arrangement consisted of a 2-step pulley on the motor driving to an intermediate shaft equipped with a 3-step pulley that, in turn, drove a matching pulley attached to the main spindle. While the drive from the motor used a single V-belt, the 3-step to 3-step drive employed two side-by-side belts for each speed. While simple, efficient and reliable, the drive suffered from being hidden away at the back of the machine, under a cover, and so inconvenient to access and change.
Instead of a conventional overarm with a detachable drop bracket on the end to hold the end of the cutter arbor, the JMB horizontal had a one-piece affair, very wide at the back but narrowing towards the front where it was curved downwards through 90° to provide a bearing housing. The wide rear section was formed with V-edged sides, complete with a gib strip and adjuster screws, that slid into matching ways machined into each side of the column's top face. A clever and economical way of providing a rigid support for the cutter arbor, the overarm was locked in place by two ball-tipped levers.
Of the plain type - and so lacking a quill feed that would have made it so much more useful - the vertical head took Schaublin 20 collets and could be swivelled through 180° each side of vertical. Equipped with neat, narrow knurled rings to aid the grip of by oily fingers, the table feed-screw zeroing micrometer dials appear to have been locked by a unique system that prevented a change in setting - knurled rings surrounding each handwheel's securing nut that pulled them inwards.
With "hand spotted" V-edged ways, micrometer dials with neat, narrow knurled rings for finger grip, a robust appearance, a standard-fit light unit and obvious attention to detail, the JMB was an impressive little miller - a sort of "Centec" on steroids. Most examples appear to have been supplied complete on a cast-iron stand with coolant equipment and a dividing head with tailstock - and to have come from surplus German army stock. With JMB being, it's reported, a company concerned with armaments, it's likely that it was also intended for use in a truck-mounted mobile workshop. Other versions of the this model have also been found, some with lever feed to the table's longitudinal feed, tables with a single central T-slot and drive direct from motor to the spindle.
JMB also made a small but rugged drill press, this being a tightly-constructed machine with a removable round table machined with four radial T-slots, an integral motor, a very simple mechanical variable-speed drive system - and a built-in light. Giving a range from 1500 to 5000 r.p.m. the variable-speed drive system was a friction type, the 250 Watt, 2800 r.p.m. 50 Hz motor able to be slid backwards and forwards by moving a lever on the left-hand face of the main body. On the motor spindle was a rubber tyre, this pressing against the face of a steel disc attached to the main spindle. As the motor was moved forwards towards the centre of the disc the speed was reduced, while moving it backwards caused it to increase. A simple system and one perfectly suitable for drilling small holes up to 0.25" (6.5 mm) in diameter with the supplied chuck, a high-precision Albrecht, confirming this intended use. A number of machine tools have been built with a similar friction drive including the Bulgarian Mashstroy lathe, American Elmco, Schaffner and Onan lathes, the German Robling and Boley F1 high-precision watchmaker's lathes - and some examples of German Klopp and American Hendey shapers. A reversing cone-type friction drive was also used on the English Oldak and Apex tapping machine, but this was not a variable-speed type.
If you have a JMB machine tool of any type, the writer would very much appreciate hearing from you to discover more about these appealing, well-made machines..