wrote:

Never used such a large core drill, but with a 45mm I always go
striaght in with guide bit and core as one. I can't see why you wanted
to pilot the guide bit right through first.

Two reasons for drilling a pilot: it lets you drill from both sides and
still have a fair hope of meeting in the middle, and it also *can* make
drilling quicker in some materials.

(I have found dome types of brick that cut rapidly with the diamond of
the core bit, but take forever to drill without hammer action on the drill)

--
Cheers,

John.

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