Having used a UMA horizontal borer for much of his daily professional life, a Berlin-based engineer found that he missed its useful versatility and easy adaptability for machine complex components - especially the facility provided by the built-in rotary table.
Looking in a Schuchardt & Sch?/a>tte catalogue for 1921 he came across a horizontal borer by Lucas with a bed that reminded him of an old gear measuring machine he had saved from the scrapyard some twenty years earlier.
So, the idea was born to build a 1/5th scale replica of the Lucas using the bed element of the gear machine. The columns for headstock and tailstock were cast locally using patterns made by an elderly joiner with other parts machined from the solid.
Working only from the brochure pictures, the model took two years to complete and is now, at the end of 2011, almost functional. To improve usability two main alterations were made: instead of the original spindle drive (through a gearbox) belt drive was fitted to obtain the higher speeds necessary with the smaller scale and, to improve rigidity, the horizontal spindle feed was omitted.
350 mm long and 180 mm wide the table has 175 mm of cross movement and 250 mm longitudinally - with the unit holding the headstock, tailstock and spindle housing able to be moved through some 220 mm up and down. An automatic feed is provided on all three axes, in all directions, by a 3-speed gearbox taken from a lathe. However, the table runs through its maximum travel only towards the spindle, this being the direction in which an automatic stop is fitted. To bring the speed down from the electric motor a pair of worm gears are employed that give a combined reduction ratio of 90 : 1 (the reverse gears for the up and down movement are also in the same gearbox, at the right-hand end of the machine, while those for the table reverse are enclosed under a hump in the back of the table end plate).
In order to remove backlash from the spindle head, the original Lucas employed a heavy counterweight that hung on a chin down the back of the head-support column. As the replica requires this position for the drive system, the chain is arranged to pull against a long spring.
Arranged to give six spindle speeds, the drive system uses two belt drives tensioned by an eccentric bearing holder. The main spindle has a No. 3 Morse taper nose with the usual slot provided to allow the insertion of a wedge.
Held down by just two bolts, the rotary table can be quickly removed and replaced.
An exceptionally fine job, by a skilled builder.