It's now several years out of date, and I'm working from memory, but in the
past I worked
at Black & Decker in their research lab. Among the other things I did was
testing and
evaluating drill bits.
Most of the coatings make a sharp drill bit dull. They are sprayed onto the
bit after it
has been formed and sharpened. This negates the sharp cutting edge obviously.
Sometimes the bits are sharpened after the coating is applied, negating the
coating.
About the only area that coatings consistently make sense is on the sides of saw
blades used on wood. There it can work, (can, not necessarily will). But for
drilling
metal, it doesn't matter.
The funny shaped points, like the Bullet from B&D, do help. The bit centers
better,
cuts quicker, and tends not to bind on exiting, especially in sheet metal. But
you
have to select your size correctly the first time. If you're drilling big
holes, you also
have to have enough drill motor as well.
Almost all of us use the drill wrong. We spin it too fast, put too much
pressure
on it, and don't use an approprate lubricant/flushing/cooling agent. Hence our
bits get dull and break. With genuine proper use, even cheap ones tend to
last a surprisingly long time.
You can readily re-sharpen drill bits in a grinding wheel. You will get better
results with a good drill resharpening machine, but you will do better by hand
then with a cheap drill resharpening machine. Just attempt to roughly
follow the original shape. At the worse, you won't succeed, and you'll
just replace the dull bit, something you were already going to do.
By and large, you get what you pay for in drill bits. The cheaper ones
tend to not hold an edge as well. I've had some really cheap ones
bind and untwist themselves they were so soft. Spending a little
money to buy a recognizable name brand at Home Depot will
serve you quite well. I wouldn't advise taking it to the level of
buying Snap-On drill bits though. Very expensive, and they are
made by B&D anyhow.
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