Sunday, September 6, 2009
Although the triangular bed might be considered a trade mark signature for many makes of precision lathe from the late 1700s to the late 1800s - the most famous being Henry Maudsley's revolutionary screwcutting lathe of around 1800 - its use also extended to small lathes for watch and clock work with the original machines produced by the well-known Gustav Boley (G.Boley) being of this pattern.
Because draw-in collets retained by a threaded tube passing up a hollow headstock spindle had yet to be invented - that was a development first incorporated in the American Webster Whitcomb lathe of 1888/9 - the headstock of the Glashütte had to be designed in an ingenious way. This was accomplished by separating it into two sections with that on the left (its shape strongly reminiscent of watchmaker's "turns") supporting a 2-step pulley with the drive transmitted, through a pin and dog, to a spindle supported in the other, right-hand element. This arrangement left a length of spindle exposed along its middle section through which was cut a slot, matching one also broached through each collet's solid 5.3 mm diameter stem. To lock a collet in place a long key was passed through the slots - leaving its ends protruding from each side of the spindle - and a knurled-edge ring screwed backwards against it. Although this assembly performed perfectly it required advanced standards of engineering craftsmanship to work accurately - craftsmanship that - without the aid of yet-to-be-invented shaping, planning or grinding machines - would have involved the finest of hand-fitting skills.
An unusual attachment for the time - and one that was remarkably sophisticated and delicate in operation - was a compound slide rest. Fitted with beautifully-made horn handles this followed customary practice by using ordinary right-hand threads - so giving a "cack-handed" operation where turning the screw "inwards" caused the slide to move "out". The rest of the lathe also reflected early 19th century ideas - with even the fixed steady mimicking those used on larger lathes having a series of different diameter bevelled holes around the periphery of a disc.
The Glashütte is very rare, only one having come to light in recent years. If you have one, the writer would be interested to hear from you..