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Rear face of an early Sanford Model SG miniature horizontal grinder
Model SG - First Generation: serial numbers AA1 to 396
Distinguishing characteristics: (1) The table was 17" wide and had a raised plinth on the left side of the chuck mounting boss caused by the gear rack being recessed into the underside of the table. There were 4 oil cups on the table top, one at each corner of the chuck mounting boss. (2) Table travel was a nominal 4" x 6". (3) The side faces of the cast-iron base flared outwards in a large radius. (4) Handwheels had 3 spokes and no web-like counterweights. (5) The vertical leadscrew and its associated top-mounted bevel gears projected above the uprights and were covered with two thin, fairly complex aluminium castings. (6) The upright was attached to the base with four cap screws, two being visible on each side (7) Motor 1/8 hp, 3450 rpm. Pictures of this early example continued below.
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No expense spared: on early models the transverse feed screw was machined from a solid bronze casting
Later types has a nut in cast iron with a replaceable, threaded bronze insert
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Front face showing the simple, spoked handwheels without the later counterweights
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Left-hand face of the base
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Right-hand face of the base with switches and plug socket for the electrically-powered magnetic table
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Plan view: at the top, between the V and flat ways, can be seen the cast-in stop to limit table travel
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On this early model the early machines the vertical lift screw was fixed rigidly to the spindle carrier and threaded through the top bevel gear, this being turned by a handwheel. Hence, as the bevel gear rotated, it drew the screw upwards to protrude above the column while lifting the spindle carrier - the exposed screw being covered by the guard shown to the right.
In the later, modified design, the leadscrew was threaded into the spindle carrier and pinned to the top gear and so rotated with it. Hence as the screw rotated it caused the carrier to rise but with the screw remaining inside the casing
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Underside of the table - on this example the rack is recessed into the casting, resulting in the casting requiring a raised "plinth" to the left of the table's centrally-positioned mounting boss for the magnetic chuck
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Late-model vertical feed nut (with bronze insert) and (to the right) the diode power feed for the magnetic chuck
A small electrically-excited magnetic chuck was offered from the beginning of production, the necessary rectifier unit being housed within the base and suitable plugs, wiring and switches provided as part of the installation. The earliest version of the power supply used a Lafayette #4612, type 80, full-wave rectifier vacuum tube of only 1/8 amp output, the components being fitted to a metal plate inside the base. Later versions used a solid-state diode providing only half-wave rectification, although this was boosted by a matched capacitor. This much smaller circuit mounted directly on the switches, isolated by a fiber sheet, with the switch positions marked "On", "Off" and "Demagnetize". To replace the old, now-unobtainable components, a modern solid-state, full-wave bridge rectifier power supply has been designed and the schematic is available on the Internet.
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Original Sanford magnetic chuck and its electrical system
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Left: and original 4 MFD capacitor
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1951 maker's illustration of the magnetic
chuck and its electrical supply system
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