Commando cylinder head bolt sizes

1/4" BSW You need to find this socket in a 3/8' square drive. In addition, the same size combination spanner (flat not offset) and grind the ring end down to fit over the relevant nuts. As a general rule, the early Commandos have British Standard Whitworth / British Standard Fine fittings on the engine /gearbox and Unified Fine or Coarse (UNF/UNC) on the frame. These latter screws will suit your Imperial AF (across the flats) spanners and sockets.

According to Mick Hemmings if you get new nuts from Andover Norton they now come with 13mm size hexagon nuts. EBay is a good place to look for good quality tools not just cheap ones. I got a new Britool 3/8whit 3/8 drive socket delivered to my door for just £4.30

According to Mick Hemmings new genuine Andover Norton nuts are made of 13mm hexagonal size if you are replacing them not reusing them.

EBay is a good place to look for quality tools not just the cheap nasty ones, things like the whitworth socket needed for head nuts that normal outlets don't stock these days can just come through post. I got a new Britool one for just few pounds, its worth having a look instead of buying an old worn thing or some cheap rubbish at a show or car boot sale.

It's worth looking for a cheap secondhand spanner if you need to grind it down to fit tight spaces, rather than buying a Britool and butchering it.

Cheers, Lionel