Also known as Sems screws, these screws have a washer that’s permanently attached but rotates freely. The washer has sharp teeth around the outside edge that bite into the screw and the material it's installed on for vibration resistance. Twice as strong as low-strength steel screws, these Grade 5.1 screws are suitable for fastening most machinery and equipment.

Also known as Sems screws, these screws have a permanently attached but freely rotating tooth lock washer that grips the screw and your material for vibration resistance. When a wrench won’t fit, turn these screws with a slotted screwdriver instead.

With a tensile strength of 180,000 psi, these alloy steel screws are among the strongest we carry. They are stronger than Grade 8 steel screws and more than two and a half times stronger than stainless steel screws with split lock washer. The split lock washer helps to resist vibration.