Collar 02 : (n) (1) A coupling device used to join two lengths of pipe, such as casing or tubing. A combination collar has left-hand threads in one end and right-hand threads in the other. (2) A drill collar
US Department of Labor, Occupational Safety & Health Administration (OSHA), Oil and Gas Well Drilling and Servicing eTool, Washington, DC. This is an abridged version of the Dictionary of Petroleum Terms provided by Petex and the University of Texas Austin, USA 2001. http://www.osha.gov/SLTC/etools/oilandgas/glossary _of_terms/glossary_of_terms_a.html, (Oil Well Drilling Sci and Tech - Amer) {492}
