Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 138,129 pages of information and 223,036 images on early companies, their products and the people who designed and built them.
of Carn Brea, Redruth, Cornwall.
formerly R. Stephens and Son
1913 Private company.
1914 Rock Drill Manufacturers. Employees 200. 
1937 Company made public.
1940 Advert for rock drills and other mining tools. 
WWII Largely concerned with making armaments
1945 Advert for the Climax fettling grip, an air operated vice for use in foundry and fitting shop. 
1951 Introduced Maxam pneumatically controlled valves and air cylinders
1951 Became a subsidiary of Holman Brothers
1956 Maxam products were being used for automation of industry at home and abroad
1961 Manufacturers of rock drills, pneumatic drills, electric coal and stone drills, electric drills, portable and stationary air compressors. Manufacturers of "Maxam" automation equipment. 
Presumably connected with Maxam Power