In 1906, Sime was the founding president of the Dundee and District Union of Jute and Flax Workers. Two years later, he became its general secretary, and for many years the union thrived. It became increasingly hostile to the rival Dundee and District Mill and Factory Operatives' Union, which was opposed to strikes, and by 1919, it was the dominant union in the city, with 20,000 members.
In 1923, Sime led a strike at the Camperdown Works; although the workers there remained solid in support of the action, workers elsewhere in the city did not undertake solidarity action, and after many weeks, the strike was lost. Despite the defeat, the union remained active, and Sime remained prominent.
In 1925/26, Sime and local Member of Parliament Tom Johnston visited Calcutta to investigate working conditions there, and reportedly positively on the recently-established Bengal Jute Mill Workers' Union.
Sime served on the Management Committee of the General Federation of Trade Unions from 1921, becoming chair in 1928 and 1929, and later being a trustee. He retired in 1941, and died two years later.
- Arthur Marsh and Victoria Ryan, Historical Directory of Trade Unions, vol.4, p.304
- Gordon, Eleanor (1985). Women and the labour movement in Scotland, 1850-1914 (PDF). Glasgow: University of Glasgow. Retrieved 29 May 2019.
- Cox, Anthony (2013). Empire, Industry and Class: The Imperial Nexus of Jute, 1840-1940. Routledge. pp. 111–144. ISBN 1135127301.
- "Obituary". General Federation of Trade Unions Annual Report (44): 21. 1943.
|Trade union offices|
| President of the Dundee and District Union of Jute and Flax Workers
| General Secretary of the Dundee and District Union of Jute and Flax Workers
Thomas Matthew Ferguson
| Chair of the General Federation of Trade Unions