How do I remove a 3D print stuck to the glass build plate I printed a model and now I can't remove it.

I have been chiselling away with a putty knife and made little or no progress.  I even heated the bed up to 70&nbsp;&deg;C.  That really didn't seem to help.

Last time, I put it in vice, and tried to free it that way, but instead I broke the glass.

Suggestion?
It's useful to know what material you used for the print. Also, you've referenced the glass that broke in the vise, which implies a glass bed, but did you use any adhesive spray or other application?

Allowing for all of this unknown information, there may be a solution for your release. Our library makerspace has a small bottle of 50-50 water/denatured alcohol, although isopropyl alcohol should also work if your glass is not coated with a special film such as PEI. Heat up the surface of the glass to your usual temperature (50-60°C) and apply a few drops of the mixture to the edge of the print.

It will evaporate pretty quickly, but some of it will work under the glass/model interface. Apply a bit more while the glass is still warm. Continue to apply until the the evaporation is no longer accelerated.

Considering the difficulty you are experiencing, it may be necessary to repeat the heating sequence multiple times in order to get enough wicking of the liquid to effect a release.