Accession No

6500

Brief Description

Bench micrometer, ‘millionth’ measuring machine, by Sir Joseph Whitworth & Co., Manchester, English, 1893

Origin

Manchester, England

Maker

Sir Joseph Whitworth & Company

Class

engineering; metrology; laboratory apparatus

Earliest Date

1893

Latest Date

1893

Inscription Date

1893

Material

Steel; brass; wood (mahogany?); paint

Dimensions

[micrometer] 725mm long x 300mm deep x 380mm tall [micrometer in box] 915mm long x 465mm deep x 480mm tall [Standard length gauges in box:] 585mm long x 325mm deep x 85mm tall

Special Collection

Provenance

Donated by an individual at the Engineering Department of the University of Cambridge, on or before 07/06/2011.

Inscription

[On micrometer:] “Sir Joseph Whitworth & Company Limited Manchester”
“No. 89 Trade Mark 1893”
[On the standard length gauges:] “Presented By Sir Joseph Whitworth & Co. Ltd. Manchester 1893”

Description Notes

Bench micrometer, ‘millionth’ measuring machine, by Sir Joseph Whitworth & Co., Manchester, English, 1893.

Bench top precision hand-crank micrometer, so called ‘millionth’ machine because it can measure to a millionth of an inch. Sits loose in a wood-framed glass box case. Comes with 12 standard length gauges in separate fitted wooden box.

6500.1: Micrometer consists of a sturdy steel frame, holding a precision perpetual screw. On top of frame are two cradles for holding object to be measured. Fixed at one end of the frame next to one cradle is a measuring pin attached to a large brass wheel that can move the pin back and forth in line with frame. The large wheel is graduated into 500 equal divisions. At other end of frame next to the other cradle is a similar measuring pin on a moving platform, which is attached to the precision screw. This platform can be moved back and forth by a brass wheel at the end of the frame. The moving platform has an attached scale that moves across a linear graduated scale on the frame, graduated in both inches and millimetres. The measuring pin on the moving platform can also be moved in and out precisely by another small brass wheel, graduated into 250 equal divisions.

The frame for the measuring pin on the moving platform is inscribed “Sir Joseph Whitworth & Company Limited Manchester”. The frame for the measuring pin on the fixed platform is inscribed “No. 89 Trade Mark 1893”.

In the object’s case is a loose piece of card with “Whitworth ‘Millionth’ Measuring Machine 1893” written in manuscript. This was presumably placed there by a lab technician in the engineering department, as the object was displayed after it ceased to be used.

6500.2: 12 x precision standard length gauges in fitted wooden box. Each gauge is a stainless-steel rod, of four flat sides with bevelled edges, tapered to a flat point at each end. They range from 1 inch in length to 12 inches in length. They are each inscribed on one face with their integer length, the standard temperature to be used (68 degrees Fahrenheit) and a more precise length, to four or five decimal places. On another face is inscribed “J. Whitworth & Co. Manchester” and on another face “Trade Mark”. In the box are also three small metal components: a flat spanner-shaped piece, and two rods with a flat circular disk about one third of the way along its length. Pinned onto the inside of the box’s lid is a types paper sheet entitled “TOOL INSPECTION REPORT ON STANDARD LENGTH GAUGES FOR THE CAMBRIDGE UNIVERSITY LABORATORY” and dated “1st MARCH, 1940”. The sheet lists minimum and maximum errors for the rids, and the new lengths that were subsequently inscribed on the rods themselves.

References

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