The launch of giant “mechanical moles” that will bore the tunnels for the east to west cross-London rail service is only months away.

It will be a major milestone for the �14.8bn Crossrail project.

Measuring 420ft and weighing 1,000 tonnes each, six of the monster machines will be used during construction.

The first two will begin work this spring, travelling the 6.4 km (4 miles) east from Royal Oak under central London before reaching Farringdon in summer 2013.

Later this year, the second pair will launch from the Limmo site in Docklands driving 8.3 km (5.2 miles) west towards Farringdon via Whitechapel and Liverpool Street.

In the winter, two more will tunnel from Plumstead travelling 2.6 km (1.6 miles) and under the River Thames to north Woolwich. Future work includes the tunnels between Pudding Mill Lane at Stratford and Stepney Green.

Crossrail will pass through 37 stations and run 118 km (73 miles) from Maidenhead in Berkshire and Heathrow in the west, through new twin-bore 21 km (13 miles) tunnels to Shenfield in Essex and Abbey Wood, southeast London.

To mark the tunnel construction Crossrail has launched a competition seeking names for six of the machines.

Londoners and people living along the Crossrail route can propose pairs of names for the machines. The winning entries after a public online vote will be painted onto the machines.

Prizes will be awarded to the three entrants who receive the most votes.

These are either Eurostar vouchers or an annual family pass to Merlin Theme Parks.

Winners will also be invited to attend the tunnelling launch event at Royal Oak Portal.

To submit your names visit www.crossrail.co.uk/tunnel-comp by February 6.

* Similar to sea-going ships, tunnel boring machines traditionally have female names. Terms and conditions for the competition can be found on the crossrail website.