Ruby Loftus Screwing a Breech-ring

Ruby Loftus Screwing a Breech-ring is a 1943 oil on canvas painting by the British artist Dame Laura Knight. It depicts a young woman, Ruby Loftus, working at an industrial lathe cutting the screw of a breech-ring for a Bofors anti-aircraft gun. The painting was commissioned by the War Artists' Advisory Committee (WAAC) as part of the British war effort in the Second World War, particularly to encourage more women to work in factories. It is one of the largest pictures the WAAC commissioned and is in the realist style.

The painting shows Loftus, bent over a lathe, cutting the screw threads of the breech of a Bofors anti-aircraft gun. Women dominate the picture, and only one man is visible, in the background. Loftus was then 21 years old and had become an expert in the production of breech-rings—in seven months, rather than the several years it normally took. As she was too valuable to be released from her duties, Knight painted her in situ over three weeks at Royal Ordnance Factory No. 11 in Newport, south Wales.

When unveiled at the 1943 Royal Academy Summer Exhibition, the painting was extremely popular and was voted the picture of the exhibition. The image was reproduced in a large-scale poster version by the WAAC for display in factories across the country. As at 2026 the painting is held in the Imperial War Museums' collection.