Unknown Lathes No. 93
- an unusual small geared-head type -
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Found in England, of a relatively heavy build and obviously of professional manufacture, this most unusual miniature geared-head lathe has a centre height of 3.5" and a between-centres capacity of around 15". For such a small lathe the use of an all-geared headstock is most unusual, though perhaps the degree of over engineering was to allow its use for some special purpose, possibly the turning of very hard materials. The four spindle speeds were changed by four rods marked A, B, C and D - two protruding through the left-hand face of the (now home-made) headstock top cover and the other two through the end of the bed. Counting the teeth inside the headstock gives gear ratios arranged to be 6:1, 3:1, 2:1 - and direct through the box. Drive came from a large cast-iron pulley, heavily dished to clear fittings on the end face of the headstock, machined with a single groove to take a V-belt and fitting over a square drive shaft.
The lathe "bed" was constructed in two parts, upper and lower - the latter being a 24-inch long base "foot" in iron, formed with a large boss at the headstock end that was machined with a straight-sided slot. Into the slot was bolted the bed proper - a rectangular section of cast iron with a flat top and vertical front and back faces - all three acting as ways for the carriage. The result was a saddle equipped with an apron hanging down at both the front and rear, these being joined beneath the base to make a particularly rigid, box-form structure. Mounted in the middle of the underside joining plate were the leadscrew clasp nuts, the screw itself running down the underside of the bed, exactly on the centre line, and so protected from the wearing effects of dirt and swarf. As the clasp nuts were arranged to be directly beneath the toolpost, this meant that the line of thrust from cutting tool to leadscrew was as straight as it could be - and so any bending forces greatly reduced.
Not unique, but rare, exactly the same bed arrangement has been seen on other lathes including Toyo-Saki ML1; in a modified form on the miniature Rolls Royce; the home-made Petrie; when built with screwcutting the fine German-made Boley L-Types - though the latter had beds of a conventional form with flat tops and V-edged sides. In addition - and aping many aspects of the Boley bed design - was another interesting home-made lathe (of unknown origin) the "Precision"
As some parts are missing from the headstock end of the lathe, how the leadscrew was driven is not known. However, as there appears to be no room for changewheels, this would probably have been by a belt (flat or V) or even, possibly, by a short chain, as used on the Cuthbert con-rod boring machine. Built into the headstock was a leadscrew dog clutch, engagement being by a short lever that protruded from the bed's front face below the headstock.
How old is the lathe? It's difficult to say with any accuracy but, as the drive pulley looks to have taken a V belt, this would put it from no earlier than 1930s. However, as both the slide-rest feed screws have very old fashioned handles and lack micrometer dials, it would almost certainly not have been built after 1940.
So far two examples have been found - should you have one as well, please do get in touch with the writer.