Mayor Rob Ford promised today to keep Toronto's tunnel-boring equipment to build more subways, even as the TTC is courting buyers for the five-year-old machines.

'Yorkie' and 'Torkie' breakthrough on Keele Street for tunneling on the new York Spadina subway expansion. (TTC)

"We're going to keep these tunnelling machines," Ford told reporters on Wednesday.

The mayor had just had a meeting with the TTC's Andy Byford about the machines.

Ford says the two had a disagreement on how to move forward on the machines, which the TTC nicknamed Holey, Moley, Yorkie and Torkie.

Byford said it would cost $3.3 million more to buy new machines than to refurbish old ones, but that new machines would be more productive for the city.

Four tunnel boring machines were used for the York Spadina subway expansion. If left unsold, those machines will sit idle until 2018, when the city starts digging for the Scarborough subway expansion. There could be more subway projects — Finch, Sheppard and a Downtown Relief Line have been proposed by the mayor or his rivals in the election — but Byford points out those projects are even further away.

The machines were purchased in 2009 at a cost of $51.7 million. The TTC was recently prepared to sell the machines for $9.2 million in a deal that ended up falling through.

Byford says the tunnel-boring machines are too costly to store and by the time they would be used again, the technology will be outdated and the TTC will need new machines regardless.

Ford said he pressed Byford to find out if the TTC knew the useful life of the machines before purchasing them — a question Ford said Byford couldn't answer at that meeting.

Ford said he needs the machines to build more subways.

"Some people like subways. Some people like LRTs," he said. "From the feedback I'm getting, more people like subways."