BS 2A 254 to 2A 259:2019

Bolts, hexagonal head, close tolerance shank, UNJF threads, split pin & locking wire hole options, titanium alloy, various finishes. Classification: Rm 1 100-1 250 MPa (160 000-180 000 lbf/in2) at Ambient Temperature | +315°C. | Status: Confirmed, Current

1 Scope This British Standard specifies the materials, dimensions, finish and inspection requirements for titanium alloy bolts with hexagonal heads and UNJ thread for aerospace use.

CAUTION. BS A 257 bolts have cadmium as a plating material which has been restricted and/or banned for use in many countries owing to environmental and health concerns; they should not be used in new product designs. Local officials should be consulted about any concerns on the use of cadmium-plated parts. In addition, cadmium plating on titanium parts has been documented to result in stress corrosion and also solid metal embrittlement (SME) when exposed to relatively low temperatures. Accordingly, BS A 258 has been introduced as a replacement.

When considering the use of cadmium plated titanium bolts, attention is drawn to Def Stan 00-970 Pt.1/14 Section 4 Leaflet 8 which recommends certain limitations on their use.