Timber terracing and how to drill 30mm hole..?

[crumpetsolo]

I need to replace some giant sleeper type timbers that are holding up the terracing in our garden and have decided to do this myself. I can get hold of the timber - 75 x 150mm in 2.5m lengths, but they are held in place by 30mm diameter metal 'stakes' and none of the timber merchants can provide timber with pre-drilled holes so the sleepers can slot onto these stakes (replacing rotten old ones)

Any ideas what sort of tool I would need to make these holes? 30mm diameter and 150mm deep so quite big.. would a tool hire place do something? Not quite sure what to ask for.

Also what sort of timber should I be using for garden projects? Any help gratefully received!

 

[gregers]

auger or spade bit with a extension bar fitted,this i would think may work.