The Crusaders battled back into the attack zone though to set up for a dropped goal. They were patient but the Chiefs refused to yield or conceded penalties.
Eventually replacement lock Tom Donnelly knocked on and the Chiefs had won a famous victory.
The Chiefs scoring burst midway through the first spell proved decisive as they clung to a slim lead throughout the second spell to earn a place in the final against either the Stormers or Sharks.
Those sides duel tomorrow in Cape Town and if the Stormers win the Chiefs will have to travel to the Republic for their second title at the title in the series' history.
The match started with a noticeable bite as they niggled, jostled and harangued each other.
There were scuffles in midfield between Liam Messam and George Whitelock, several tussles involving Sona Taumalolo and Ben Tameifuna.
The message was clear from the Chiefs. They were not going to be intimidated in any area of Waikato Stadium nor were they going to fold in the set piece like the sides' last meeting.
They brought some sting with their attitude too. They were flying up hard on defence, giving the Crusaders little time to adjust their plans. Liam Messam broke the line for the first real incision in this sudden-death semifinal. He skipped clear with Sonny Bill Williams trailing hard and if a pass had not been intercepted by Ryan Crotty, there would have been serious trouble for the visitors.
Soon after there was.
The initials were to the fore - Sonny Bill Williams and Tawera Kerr-Barlow - before the ball was driven towards the line by Brodie Retallick and then onto the whitewash by Taumalolo.
There might have been some question about the legality of the prop's work but all referee Craig Joubert asked TMO Garratt Williamson was "try or no try?"
He ruled it was a try to the enthusiastic response of the 25,100 crowd.
Bedlam followed shortly after when Messam scored.
Robbie Robinson threaded his way upfield, returning a kick and bypassing a number of poor tackles until he was sacked by Richie McCaw.
The ruck ball came back quickly, Williams spurted through an inside channel and Messam kicked clear of the final defender.
A 17-6 lead was gold and it looked as though the Chiefs would go even further ahead when they snuffed out a Crusaders attack and countered 80m downfield.
However they were ruled to have players offside in the move and from the subsequent penalty, lineout and drive by Matt Todd, the ball was shifted to Crotty to glide across the line.
That try right on the break was crucial. It gave the Crusaders hope that a comeback was on while it dented some of the Chiefs verve.
An old rugby adage talks about moments either side of halftime as the pivotal phases in games.
The Crusaders claimed one could they repeat after the break?
It was inconclusive as Cruden and Daniel Carter traded penalties while the game continued its abrasive festering course.
It was played between the two 22s for most of the third quarter as both teams sought to negate any penalty concessions.
