Semi-Auto Lathes

Semi-automatic lathes were a late addition to the comprehensive range of machine tools used throughout the AMC factory in Plumstead, that came from the R.T. Shelley plant (Norton's wholly-owned subsidiary).

These Wickman multi-head machines, were introduced in the mid-1950s, when the company was still optimistic over their big bike sales, in order to produce the less complicated turned items more efficiently than possible by the capstan lathes.

The form of automation used in these machines was of the pre-computer age type, with the control via cams instead of the programmable logic devices in common use today.

The machines were also limited to bar work, as opposed to being able to handle the more complicated castings or forgings.

The first batch of machines were located on the ground floor in the newer extension section of the factory, adjacent to the Gearcutters.

Later on, others were installed in the area previously occupied by the Inspection Department, also on the ground floor.

The largest Wickman machines had six stations, which all worked to fixed, adjustable stops (no control as we know it today).

At each of the stations, turning tools were fed in to machine part of the shape required before returning to their start point. At the last station, the finished component was 'parted-off' from its bar.

The six turrets would then index to the next station so that, at every index and movement of the turning tools, a finished component fell off into a collector chute.

In operation, the material to be machined would pass through the spindle to be gripped by the chuck (usually a collet type) and, as the part was being machined, the entire length of bar stock would be turning with the spindle.

When the machining cycle for one component was completed, the chuck would be un-clamped, and the bar fed forward and re-clamped, ready for the next cycle.

The rear, feed end of each Semi-Auto machine resembled an enormous Gatling gun, with the feed tubes for the bar stock on the largest machines capable of accommodating 6 or 8 inch diameter material.

Supervision of the machining operation was limited to loading fresh bar stock when necessary, removing the finished items at regular intervals, gauging where necessary, and carrying out the usual machine maintenance duties (swarf removal, etc). This allowed one attendant to be in charge of several machines at one time.

For this unskilled work, the company hired many people, some from various Commonwealth countries, whose experience of engineering factories was almost non-existent.

Language and cultural differences also caused quite a lot of problems for their work colleagues, who had to pass on their instructions and ensure that the previous high standards of accuracy were not being jeopodised in this new era of working.

There were also specialist types of semi-auto machines situated on the second floor, alongside the drilling bay that handled the initial work on crankcases and gearbox housings.

This work involved drilling the set of normal tolerance bolt fixing holes as well two, more accurate, tooling holes that were needed for the next stage of operations.

The parts were then transferred onto horizontal boring machines, specially made by the Alfred Herbert Company, and clamped onto a fixture that had protruding pegs to locate into the tooling holes.

Each semi-auto machine had boring heads at opposite ends, so that one would finish the bearing diameter and then the workpiece would move to the other end to have the oil seal diameter added.

This combination of operations, on the same workpiece setting, ensured that both the bores would be concentric to each other.

The tooling holes were also used at the engine/gearbox assembly stage, as dowelling holes, to accurately locate each housing to its mating part. These two vital requirements were thus achieved in a simple manner.