wrote:

Has anyone tried those flat bits that claim to work like augers? The
point is threaded, although still flat, and the outer edge of the flat
cutter has a point on so it cuts the wood away before it rips it out,
for a cleaner lower energy job. Well, so it says...

That sounds somewhat like an expansive bit I got from toolstation...
much like a flat bit except you can slide the flat part from side to
side to change the effective cutting diameter. The "flat" section is
also profiled slightly such that it has a slight attack angle rather
than being exactly perpendicular to the wood.

As for being low energy, not a chance. I found the worm thread on the
tip tries to pull the bit through way to fast - such that it attempts to
take a 2mm thick bite out of the wood on each rotation. Rather like an
auger in a brace would. In a very powerful cordless you will have great
difficulty holding it steady, and it will either stall the drill or
twist your wrist if you are not very careful! The solution is to
pre-drill the centre hole. Then the worm screw just guides rather than
pulls. Then it is much like a spade bit. Not sure it is much cleaner,
but then again I have always found spade bits make reasonably neat holes
except for the exit.

I used it for drilling into the end grain of a newel post base (to
accept the 2" spigot on the end of the newel). In this mode it does not
pull through so fast and you can get more speed and a lighter cut per
rotation, but it still tends to switch randomly between spinning with
very little cut and then grabbing hold and sucking out half a tree in
one go.

So if you need a big blind hole of depth, then it will do the job when
not much else will, otherwise not a pleasant drilling experience.

As usual YMMV, and remember we are taking about a 10 quid silverline
version here and not the 20 to 30 quid version that most places have.



--
Cheers,

John.

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