Bill Woods wrote:

Do drill bits for use in ordinary "home use" drills get blunt with
the result that they work less well?

Yes.

I ask this because I recently used my hammer drill to make some 6mm
holes in masonry in the concrete ceiling above me and it seemed like
very slow work. When I used a smaller drill bit of about 4 to 5 mm
in the same masonry material then it was much, much easier to make

Of course the smaller bit makes a hole with a smaller area but the
difference seemed far greater than this. I wonder if my 6mm drill
bit (and maybe others) need replacing?

As you note a smaller hole will always be quicker to make anyway - even
if the 5 and 6mm bits were equally sharp. You could also consider
"opening up" a smaller hole by drilling it with the smaller sharp bit,
and then redrilling with the larger bit.

--
Cheers,

John.

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