The components are:
(1) 2 inch x 12 inch pipe nipple
(1) 2 inch pipe cap
(1) 2 inch x 1¼ inch reducing coupler, or "bell" reducer
(1) 1 inch x 18 inch pipe nipple
(2) 1 inch pipe caps
All the caps are screwed tightly on their respective pipes, with no intention of removing them, but before putting both caps on the 1" pipe, the pipe is slid through the hole in the bell reducer.
The reducer acts as the cap of the crusher, and should not be overly tight when screwed on. Powdered glass may get into the threads and make them difficult to unscrew.
I've found that it's best not to put many chunks of glass in the mortar at one time, since the bottom portion remains uncrushed once a layer of powdered glass is on top of it. This is hard work for hands and generates dust. Be safe and wear gloves and a respirator. Put padding on the handle to make it easier on the hands. To download this drawing, click here.
Some photos: 
