Surely a bolt without threads secured with a split pin or similar would suffice.
Ah, don't go there mate. Chinook ZA721, Mount Pleasant 1987. 5 dead. Split Pin hole not drilled, so no split pin. Not considered an issue by MoD.
For some extraordinary reason the AAIB thought it was. BoI President instructed to say "not determined". (Evidence to ZD576 Fatal Accident Inquiry).