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Clausing 10-nch 4900 Circa 1968
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Clausing 5900 Series Lathes - Serial Numbers

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By the late 1960s Clausing lathes had become rather squarer in appearance, a styling and design change clearly seen in the 1968 Clausing 4900 illustrated below. The machine was based on a flame-hardened, ground-finished bed that was well braced between elliptically shaped, rearward-draining, swarf-clearance holes.
Made in a forged, chrome-steel the headstock spindle had a hardened nose, was bored 1
1/16", and ran on precision Timken taper-roller bearings. Two types of collet fitting were available, a simple spring-collet assembly (which used either a hand-operated or lever-type draw tube) or the wonderfully-well engineered English Burnerd Multisize collet set that ranged in capacity from 1/16" to 1". Each Multsize collet spanned a 1/8" gripping range and so could be used for both English and metric-sized material.
A conventional tumble-reverse mechanism was fitted to the changewheel drive that connected to a screwcutting gearbox of the traditional Norton Quick-change pattern with a single tumbler and open base - a design as fitted, for example, to thousands of early South Bend lathes. A knob protruding from the headstock-end guard was used to select either fine feeds or screwcutting ratios.
The drive system on the 4900 consisted of a motor, mounted in the base of the cabinet stand, driving upwards to rigidly-mounted, Multi-V Step countershaft unit. Reflecting contemporary changes to drive technology, from there the motion was taken by a "toothed" belt to an overhung pulley on the end of the headstock spindle. To change speeds the stand door had to be opened, an over-centre lever operated and the motor to countershaft V belt repositioned on its pulleys. Twelve spindle speeds were provided: in backgear: 52, 62, 75, 125,174,237 rpm, and in open gear: 370, 450, 540, 900, 1250, and 1700 rpm..

Clausing 10" 4900 Circa 1968