Is 400F oven too hot for a Hocking pieplate for the glass with which it has been manufactured?

A 400°F oven is generally safe for Hocking pie plates, as they are designed to withstand typical baking temperatures. However, it's always best to check the manufacturer's guidelines for specific temperature recommendations. If the pie plate is free from chips or cracks, it should perform well at this temperature. For added safety, avoid sudden temperature changes to prevent thermal shock.