In article . com,
RayV wrote:
A while back I had to drill out a bolt and went through several bits.
Dulling them, snapping them and as a bonus I also snapped a misnamed
easy-out. Buy new bits? Nah, they cost too much for a decent set
besides I have probably 100 drill bits. I gotta figure out a way to
sharpen them.
DAGS. Keeps coming back with buy a drill doctor. I find the thing
from Lee Valley and others that holds the bit at the correct angle to
bench grinder for $10.
http://www.leevalley.com/wood/page.a...072,43086&ap=1
The DD and the angle guide don't seem to be doing anything fancy so I
think why can't I just do it myself. Here's what I'm thinking please
tell me if you think it will work.
Cut a wedge at the proper angle
Chuck the dull bit in my drill press
Clamp the wedge and a stone or fine file to the DP table
Lower the dull bit against the stone or file
Keep bit oiled and cool
Done
Unless I'm missing something doing it that way would give me the same
results as the grinder jig and probably the DD too.
The method you propose will not duplicate the geometry of a correctly
sharpened drill bit. I'm not sure I can explain it verbally, but here
goes: the surface that trails the cutting edge must be angled so that
iit provides a clearance angle for the cutting edge. If the bit was
sharpened by merely spinning it against a fixed abrasive surface, there
would be 0 deg clearance angle. Using such a bit would be equivalent
to trying to lift a shaving with a chisel while keeping the flat back
flat against the wood. IOW, without the clearance angle, the cutting
edge cannot actually contact the work.
The good news is, in larger drill sizes, it is not too difficult to
sharpen a drill bit to effectively cut wood using an ordinary bench
grinder. With more practice, you can do a passable job at sharpening a
bit to effectively cut metal as well. There are some good books out
there that will explain how, or perhaps you know someone who already
knows how. I was lucky enough to have an old machinist show me how over
30 years ago. That guy would actually take a drill bit to the grinder
and custom grind it for the type of surface he was using it on. BTW,
if you are only drilling wood with a twist bit, you can steepen the
effective cutting angle quite a bit (no pun intended) than the general
purpose metal twist bits and they will work a lot faster & cooler.
Smaller sizes are tougher to regrind by hand, depending on skill,
eyesight, steadyness of hand, etc. For me, anything smaller than 1/4"
or maybe 3/16 is a throwaway.
--
Make it as simple as possible, but no simpler.
Larry Wasserman - Baltimore Maryland -