A thick-wall steel collar, the inside surface of which is tapered to fit
two serrated-face taper sleeves. The assembly may be fitted at any point
over a casing or pipe and serves as a drive collar in sinking casing or
pipe by driving and chopping. Also called self-tightening jar collar;
self-tightening jar coupling; Simmons jar block, Simmons jar collar.
Long
Source:
Dictionary of Mining, Mineral, and Related Terms
