These numbers are from "Fly Tyer".

Uni 3/0 – 213 denier
Uni 6/0 – 135 denier
Uni 8/0 – 72 denier
Uni Big Fly – 400 denier

Danville Flymaster 6/0 – 79 denier
Danville Flymaster + – 237 denier
Danville Flat Waxed Nylon – 223 denier

Wapsi (Ultra 140 – 140 denier) and UTC (UTC 280 – 280 denier) list thread size in denier.