what is sharp steel or weak steel case in tooling?
sharp or weak steel is usually where you have very long and thin pieces of steel in the tooling, usually between ribs are too close to each other or they meet the outer form at a tight angle leaving a point in the core tooling.
i hope this helps :)
it all depends on the length of the piece of steel as i rule i try and keep it above 0.5mm but for very short section you can possible go slightly smaller but for long thin section its best avoided. if you have thin steel in a tool your tool life will drop thus you will get less parts from a mold.
As explained by Carl, Sharp steel or Hot Blade is caused when long and thin pieces of mould steel are subjected to repeated cycles of heating and cooling, this causes fatigue failure in the tooling. So, its always recommended to maintain some gap between engineering features like ribs (which are thin and long), generally is 2t (where t is nominal wall thickness) or 5mm whichever is greater.