BA Machine Screws Slotted Cheese Stainless Steel Fully Threaded Round Cylinder Bolts A2 Roundhead British Association Threads Fasteners Hardware Manufacturer Supplier

The BA machine screws are the screws with a thread of a largely obsolete set of small screw threads, the largest being 0BA at 6 mm diameter. They were, and to some extent still are, used for miniature instruments and modeling. Ever Hardware provides custom-made BA machine screws and customizable packaging.

They are unusual in that they were probably the most “scientific” design of screw, starting with 0BA at 6.0-mm diameter and 1.0-mm pitch and progressing in a geometric sequence where each larger number was 0.9 times the pitch of the last size. They then spoiled this by rounding to 2 significant figures in metric and then converting to inches and rounding to the thousandth of an inch. This anticipated worldwide metrication by about a century.

The Thury thread was different in that it went both positive and negative all the way up to a size of -20 which was 75.2-mm diameter by 8.23-mm pitch. The Thury numbers were rounded to three significant figures. The Thury thread form had the crests rounded at 1/6p and the roots rounded at 1/5p so the thread angle was close to 47.5° but not exactly. This was simplified in the BA thread definition by defining the thread angle to be 47.5° exactly and the thread form to be symmetrical with a depth of 0.6p.

Stainless steel does not readily corrode, rust or stain with water as ordinary steel does. However, it is not fully stain-proof in low-oxygen, high salinity, or poor air-circulation environments. There are different grades and surface finishes of stainless steel to suit the environment the alloy must endure. Stainless steel is used where both the properties of steel and corrosion resistance are required.

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