Think of Strong Hand Tools’ Expand-O pliers like a pair of Vice-Grips (or Vice-Grip knock-offs) in reverse — squeezing the handles spreads and locks the jaws rather than clamping them down. The “jaws” can exert 500 lbs. of spreading pressure and, just like your Vice-Grips, a lever quickly releases them when you’re finished spreading.
Strong Hold Tools uses heat-treated steel in the construction of the Expand-O pliers and nickel/chrome-plates it to resist corrosion. They sell two versions: the 6-1/2″ PE6 and 10″ PE10. The jaws of the PE6 have a 3/4″ stroke and the PE10’s have a 1-3/8″ stroke. One of the jaws has a threaded hole, 5/16″-18 for the PE6 and 3/8″-16 for the PE10, so you can use a longer or shorter bolt depending on the spreading application. The other jaw swivels to keep it flat against whatever you’re spreading.
Pricing for the 6-1/2″ pliers starts at $15. The 10″ pliers will run you at least $22.