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Rajesh: Sure.
Viktor: That's the main technical issue, in terms of deciding how we form these holes. Obviously,
the technical side's not the only consideration. There's also the question of timescales - given
that there are a lot of these holes to do. And, obviously, the question of cost, as well.
b In pairs, compare core drilling and preforming with regard to the following feasibility
issues. Which technique is most suitable for the situation in Exercise 9a?
cost precision timescale

c ► 6.5 Viktor and Rajesh are assessing the most suitable method of forming the holes in
the walls. Read the conversation and compare their answers with yours.

Viktor: In terms of cost, preforming is obviously a lot cheaper, because all you need are plastic
tubes, which are cheap to buy, and quick to put in. If we do it that way, it'll be dead easy, and
it’ll cost peanuts. Whereas core drilling will be slow, it'll be quite a painstaking job. But...
Rajesh: But core drilling's more accurate, clearly. Viktor: A lot more accurate. I mean,
sometimes, you can get away with preforming. If you need to get within twenty mil, then it’s
perfectly feasible. Ten mil is - it’s achievable, but it's stretching it. Anything less than ten mil,
and there's no way you can do it.
Rajesh: And what sort of tolerance are you looking for?
Viktor: About ten mil.
Rajesh: So it's borderline, then.
Viktor: It’s a tall order. The safe bet would be going for core drilling.
Rajesh: The problem is going to be the schedule, though.
Viktor: Exactly. I mean, to diamond drill the number of holes we're talking about will take, um ...
Rajesh: It'll take forever and a day, won't it? Whereas if they're preformed, they’d be ready as
soon as the walls are cast.
Viktor: But if half of them are in the wrong place, it’ll cost an arm and a leg to put them right.
Because if they're wrong, it’s not just a question of drilling new ones in the right place. If they’re
slightly out of position, they have to be filled in, first, with cement, to avoid having two holes
overlapping. So putting them right is easier said than done.
Rajesh: Sure. So as I see it, the key issue here, in terms of feasibility, is the tolerance. If the holes
can be bigger, and there’s more play for the bolts, we won't have this problem.

d ► 6.5 Listen again and answer the following questions.
1 What are the advantages of using preformed holes in terms of cost and timescale?
2 What’s the main disadvantage of core drilling the holes?
3 What tolerance can easily be achieved with preformed holes?
4 What tolerance is required for the holes on this project?
5 What’s the risk of using preformed holes?
6 What key feasibility issue does Rajesh identify?

e Complete the following expressions from the conversation using the words in the box
and indicate the degree of feasibility each expression describes.
borderline; dead; forever; leg; painstaking; peanuts; perfectly;
stretching; tall; way;

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