Drawing of Peter Ewart's design for a cylinder boring mill, 1795, scale 1:36, from original drawing in Boulton and Watt collection at Birmingham

This drawing, 22 inches by 20 inches in size, was copied from the original in the Free Reference Library, Birmingham, and represents the cylinder boring machine designed in 1795 by Peter Ewart for Boulton and Watt's new Soho Foundry, but not actually constructed. In the event a horizontal mill was built instead.

From 1776 until 1795, Watt's cylinders were cast and bored by John Wilkinson at Bersham Ironworks (see inventory no. 1927-985). James Watt, Junr, writing to Matthew Boulton on June 8, 1795, said: 'Inclosed you have Mr Peter Ewart's plan for perpendicular boring, which I address to you as the advocate of that mode of operating.'

The proposed mill has a solid vertical boring bar, 12 in diameter, and 14 ft 6 inches long, supported by a timber framing which is housed in a masonry pit. It is rotated by a large spur wheel at its lower end, driven by an inclined shaft and bevel gearing from a horizontal shaft at the ground level. The sliding cutter head has a longitudinal keyway, and the feed is obtained by two racks attached to a loose ring on the cutter head, raised by pinions on a transverse shaft at the top of the machine. The cylinder is suspended by its upper flange from transverse timbers and secured laterally by two sets of four struts with adjusting screws.

A cylinder 28 in diameter and 7 ft 3 in long is shown in position.