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An early 1950s Model 750 with a beautiful (but less expensive than nickel plate) crackle-black paint finish. The centre height was 7.5 cm, (giving a swing of 67/8") and the bed 22" long - with a between-centres' capacity of 12". The spindle on the model illustrated is of the 12,000 rpm ball-bearing type and fitted with a with a Spring-bind brake assembly which simultaneously stropped the spindle and opened the collet. In the illustration the lathe is driven from underneath by an infinitely variable-speed motor made by the Master Electric Company of Dayton, Ohio". This was an all-metal unit, of an essentially simple "swash-plate" design, where the drive and output shafts, (splined and laying one above the other) were each fitted with two opposed cones, one fixed, one free, which engaged with the tapered sides of a large ring which passed between them. Turning the external control wheel resulted in the upper right-hand and lower left-hand "free"cones being moved simultaneously along their respective shafts - so altering the radius at which they engaged with the ring and hence changing the ratio between them and their relative speeds. The unit selected for the 750 had a speed range of 500 - 5000 rpm. These devices were beautifully made - but very expensive; by the mid 1950s a 0.25 hp unit was $350, against a list price of around $60 for an ordinary motor. Despite this, many were to be found in applications as diverse as food-packaging machinery and military hardware - and at a stroke they solved the problem of building a speed-reducing countershaft unit for a small lathe or miller. However, when they go wrong, they can be difficult and expensive to repair and by the late 1960s had been replaced by various forms of cheap electronic speed control. For a wider view of the Model 750 and its installation, click HERE. For an illustration of the Master motor unit, click HERE.
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