The phrase 'as reliable as clockwork' is correct and usable in written English. You can use it to describe something that is very dependable or regular, like a person who always shows up on time for work or a machine that functions correctly every time it is used. For example, "My grandfather is as reliable as clockwork - he's never late for an appointment or obligation."
He works his choice of hours but, according to his colleagues, he is "as reliable as clockwork".
Introspection is not as reliable as observation.
If only control was as reliable as build quality.
– I'm not as reliable as I first suggested.
For years, the pattern here was as reliable as sunrise.
"ALL women are as reliable as my bible!
The lovable Brit is about as reliable as it gets.
My internet connection was about as reliable as Charles Kennedy.
It's as reliable as she is.
And, reliable as clockwork, where a sector undergoes technological disruption, we can expect to see a flurry of investment, dealmaking and M&A activity.
Firstly, earthquakes don't happen as regularly as clockwork.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union