The guard was assaulted during the attack in East Kilbride as four men broke into his hut and threw him in the back of their getaway van.
The gang then stole a JCB and made off in that and the van before they crashed and abandoned the digger near to Broadbent Farm, East Kilbride.
The man was then driven in the back of the van a short distance before the suspects abandoned both him and the van near to Langlands Golf Course before making off in a red Seat Leon car.
Police officers arrived shortly thereafter and found the man in the rear of the van and weapons nearby. He was taken to Crosshouse Hospital where he was treated for serious head injuries.
Detective Inspector Paul Swinburne said: “This was an horrific and senseless attack on an innocent working man and I am determined to find the people responsible for this attack.
“After the suspects made off from the white van they got into a red Seat Leon with a partial registration believed to begin with SD07.
“I have no doubt that there were witnesses to this, as the suspects abandoned a white van, crashed a large JCB and made off at high speed in a red Seat Leon”