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Made by the Machinery Manufacturing Company of 1915 East 515T Street, Vernon, Los Angeles, California, the Vernon "Combination Vertical Milling Machine & Jig Borer" was aimed at that end of the market looking for a compact, inexpensive jig borer for use in a regular repair shop or smaller toolroom. Although intended just for jig boring, like many of its kind, especially larger models, it was also possible to press it into use for general-purpose milling - though if long-life accuracy was to be maintained, restricting it to its original purpose of boring holes would have been a wise precaution. Vernon manufactured a range of horizontal and vertical millers, jig borers and shapers but, by the mid-1940s, had either been absorbed into the Sheldon Machine Company, or arranged a marketing agreement whereby the jig borer, a shaper and a horizontal miller were included in the main and subsidiary Sheldon catalogs and advertised as "Sheldon -Vernon" products.
Manufactured from the 1930s to the very early 1950s, the jig borer was not dissimilar in size and configuration to the contemporary American Linley of the same era. Showing its long-lived appeal, during the 1970s the design was resurrected by the Chin Tsan Machine Company of Taiwan as their Model CTV-700 - a machine with few mechanical differences and cosmetically very similar - even to the vertical bracing on the main column and stylised horizontal lines on the side face of the vertical head.
Like the Linley, the Vernon was constructed along traditional jig-borer lines with a non-elevating compound table and the main head arranged to move up and down (over a range of 10.5 inches) on a slideway formed on the inside front surface of the main column - the aim being to produce as rigid a structure as possible. In addition to lending itself to bench mounting, the design also allows for the use of a very wide cross slide, something that Vernon took advantage of. The head, which weighed approximately 60 lbs, was counterbalanced for ease of initial setting by a weight, suspended by a wire and chain within the main body of the machine. The spindle was made from a high-grade alloy steel (with the collet-holding nose hardened and ground) and ran in pre-loaded, ultra-precision ball bearings with the upper and lower sets separated by a hardened and ground sleeve. The drive was taken from spindle to pulley by a six-spline shaft running in ball bearings, a design that helped isolate the spindle from drive strains. The quill, which appears to have been increased in size at some point in the machine's development from 25/8" to 3-inches in diameter, was heat treated and ground finished and operated by both fine and quick-action feeds; a micrometer-dial depth stop and ruler were fitted as standard.
Heavily-built, the 21" x 6" table carried 3 (7/16") T slots and had 12 inches of longitudinal and 6 inches of cross travel along a very wide knee; the maximum distance from the spindle nose to the table surface, and the maximum travel of the knee, was 10.5 inches. Unfortunately, and doubtless to the annoyance of professional machinists working against the clock, a handwheel was fitted to the longitudinal feed screw at the right-hand side only - the machine in the photographs below, which show the handwheel on the left, was changed by the owner to suit his personal preference. The table feed screws were supported in ball bearings where they passed through the supporting end plates and the micrometer dials were of the friction zeroing type.
Carefully thought out, the drive system was arranged so that the pull of the belts did not impinge on the motor shaft - this was achieved by bolting a self-contained, cast-iron structure to the back of the column that carried, on its lower face, a 0.5 HP 1750 rpm motor. The drive was taken upwards through a flexible coupling to an extension shaft running in upper and lower bearings held in the arms of an extension fork. The drive then went forwards, via an intermediate pulley, to the main head by V belts - giving a total of 8 speeds which, for the 1947 and 1948 model years, were listed as 250, 375, 525, 775, 1250, 1850, 2700 and 4000 rpm. Efforts were made to minimise vibration from the drive system and, besides the flexible joint, all three pulleys were dynamically balanced; if a second-hand machine suffers from vibrations and rough running, it may well be that one or more of the original pulleys has been replaced by an unbalanced replacement - or a cheap, Chinese-made V-belt fitted. The belts were guarded by a cast aluminium cover - the top section of which hinged open forwards with a clamp-shell action - styled in the "streamline" style of the 1930s. Some machines were fitted with a modified drive system that allowed a wider speed range with both step-down and step-up ratios. This was achieved by fitting two multi-step pulleys to the motor shaft extension with the upper 4-step able to drive the spindle directly or, by engaging a pin, through a small pulley beneath. The small pulley took the drive to the intermediate pulley from where it was returned through a second belt to a pulley set immediately beneath the lowest and largest of the upper set. This complicated "compound" drive that resulted provided both high and low-speed ranges using a system not dissimilar to that employed on the early Atlas 9-inch lathe.
It is not unusual for machines of this type to have lost some if not all of their original collet set and, because these are retained by a screwed ring on the spindle nose and not drawn in by a bar passing through the column, the range of types that can be adapted is limited. The nose was originally advertised as being designed to accept two entirely different types of collet - either an "LB" or one with a No. 7 Brown & Sharpe outside taper - in both cases with a maximum capacity of 0.5 inches. Today, either type can be reproduced by, amongst others, Hardinge in the USA or Crawfords in the UK. It is reported by current users of the Vernon that 3AT collets will also work - just - while the Brown & Sharpe 00 collet is a rather better fit, if still not an entirely perfect solution.
When the machine was to be used as a true jig borer, to position the table accurately a method better than using the feed-screw micrometer dials was necessary. The contemporary solution was to fit a kit containing two, 1-inch range dial-test indicators and a set of seven very accurate rods from 1 to 4-inches in length and the necessary steel troughs into which they could be placed. With the machine thus equipped, the operator would have been able, with care, to position holes centres within fractions of one-thousandths of an inch.
Standing 71" high, the Vernon jig borer/miller weighed approximately 750 lbs..
Vernon jig-borer/vertical miller continued here
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