BS 21 Pipe threads where pressure-tight joints are made on the threads (old)

Is BS 21 still current?

No, it is withdrawn. BS 21 is withdrawn with no direct replacement (MechAtlas review: 27 October 2026). Check with the publisher what to use for new work.

What it covers

Former British BSP sealing thread standard.

Parts that use BS 21

• Pipe threads (BSP / NPT) (UK (BS), old)
  Inch-sized threads on pipes and fittings: taper threads seal on the thread, parallel threads need a gasket.
  Withdrawn 2016.

Official source

MechAtlas does not reproduce standards. Check the official edition at the publisher's page for BS 21 or the BS store.

Other fasteners & threads standards

• DIN 125-1 Replaced
  Washers, product grade A, up to 250 HV
• DIN 1481 Replaced
  Heavy spring pins (old)
• DIN 2999-1 Replaced
  Whitworth pipe threads (old)
• DIN 6325 Replaced
  Hardened parallel pins m6 (old)
• DIN 6914 Replaced
  HV hex bolts for steel structures (old)
• DIN 7 Replaced
  Parallel pins (old)
• DIN 7337 Replaced
  Break mandrel blind rivets (old)
• DIN 7991 Replaced
  Hexagon socket countersunk head screws
• DIN 9021 Replaced
  Washers, outside diameter about 3 x thread
• DIN 912 Replaced
  Hexagon socket head cap screws (ISO 4762 modified)
• DIN 913 Replaced
  Hexagon socket set screws, flat point (ISO 4026 modified)
• DIN 916 Replaced
  Hexagon socket set screws, cup point (ISO 4029 modified)

All Fasteners & threads standards →