stapfam

2 x 6mm allen keys and a 4 mm.

Know this is not the type you mean but it is a bolt on axle and I couldn't resist it.

Not certain on the size spanner but one spanner of the correct size that is open one end and a ring the other. Always use the ring. And the problem I found was if the cones were not set up tight enough- You would turn the Nut- Axle and cones at one end of the axle- whilst the cone at the other end would be tightening or undoing itself. So Conventional axle and make certain the Cones are tight and I do mean tight.

So that is another expense as good Cone spanners are not cheap and you need them in pairs and each size from 13 to 17 mm size. You can never tell which size you need. Give me Roller bearings any day.