I see this 'thing' on the side of lathes. What does it do?

Thanks.

http://i230.photobucket.com/albums/ee176/pofo2/Lathething.jpg

5C collet quick change lever. Used for production on man ual lathes.

"Collet closer" is a more appropriate term. "Quick change" might suggest collet swapping, which it does not do quickly.

It lets you open and close the collet without needing to stop the spindle.

ie., open the collet, push the bar through, close collet, machine the bar, cut off the finished piece, start over. . .

Part crusher. ;)

zumba said it right. it basically lets you use 5c collets on a manual lathe