Originally Posted by
Brad L
I made a stem spreader out of a nut, bolt, and a piece of sheet metal. I ground the nut to about half its thickness to fit the gap. I hold the nut with a cone wrench and turn the screw against the sheet metal just enough to get the stem onto the bars. Works like a charm. I haven’t cracked a stem yet.

Some stems have this function incorporated, both bolt holes are threaded so you put a coin in the gap and use the bolt to open it a bit.