Left-Hand Threaded Alloy Steel Socket Head Screws

Turn these screws to the left to tighten them; once tight, they stop pieces that move counterclockwise from loosening. These alloy steel screws are more robust than Grade 8 steel screws, with a tensile strength of 170,000 psi. In arid conditions, their black-oxide coating offers a moderate level of corrosion protection. Under the head, the length is measured.

If you are unsure of the pitch or threads per inch, go with screws with coarse threads, which are the industry norm. Screws that adhere to ISO 4762 (formerly DIN 912) standards meet dimensional requirements.