<p>The drive for an endless chain coal cutter includes a friction drive between the drive spindle (3) and the chain wheel (1). This includes a primary ring (5) on a flange on the spindle and a secondary ring (4) on the chain wheel. The primary ring has a set of holes (7) through it for a number of connecting bolts (8). These have pointed noses (9) to engage a sloping sided slot (6) in the secondary, and their other ends (11) are domed and rest against a centering ring (10) around the drive spindle. Two sealing rings between the primary and secondary locate in grooves in the primary ring. The centering ring is free, and has a sloping periphery in contact with the bolts.</p>
