The OEM uses a tapered bore when machining the screw hole in the part, decreasing the amount of material left between the bottom of the hole and the flat. As time progresses and the flat wears from contact with the gate, a pinhole vacuum leak is created.
ESP resolved this issue by using a flat bottom bore to machine the screw hole in the part. This increased the thickness of the material between the bottom of the hole and the flat, ultimately extending the life of the part.
The throttle gate valve (TGV) hard stop is a physical hard stop for the gate valve of a 300mm etch tool. When the gate closes, it contacts the flat of the hard stop, which forces both faces of the gate outward to seal against the housing.