I didn't get to the lathe bit part until I took an intro (Machine Trades
101) class at the local Community College. On the other hand, my nearest
"hardware store" is a Production Tool ;-)
I've taught that drill sharpening technique to a lot of guys since - but
always in person. I hope that the written instruction was sufficient for
the OP (and others) to follow. It's just ridiculous to throw away a 3"
long drill bit just because the first .005" of it is dull.
I would like to add three safety tips that apply anytime a grinder is to
1) NEVER stand in line with a grinding wheel when turning it on. If it's
ever going to shatter, this is the most likely time for it.
2) NEVER mount a wheel that doesn't ring like a bell when suspended from
a nail and given a tap on the side with a small piece of metal. It
should be presumed to be cracked and just waiting for you to turn the
grinder on with it mounted. FINISH BREAKING IT to keep anyone else from
trying to mount it.
3) Eye doctors can use tiny, but powerful, magnets to tease small chunks
of metal out of your eye ... but grinding wheels aren't metal, are they?
Wear GOOD eye protection when using a bench grinder or sanding belt.
Wear goggles. Better yet, wear goggles under a face shield. Do NOT rely
on temporary side shields. DO NOT rely on your prescription lenses.
Blind is forever.
There are other safety rules for grinders (provide for lung protection,
no grinding on the side of the wheel, keep the grinding platform within
the thickness of a dime to the wheel, and so on) but these will do for a
So buy some drill bits. They're not expensive, even for decent ones. If
you're drilling something hard, then a set of real M42 cobalt bits is
pricey but wonderful. NB - these are silver, not just a blue coating
(those are worthless).
My experience: It was supposed to work except that they mis-moulded a
chuck component making it useless. UK service backup was negligible --
maybe the US is better.
Great gadget, so long as you set the little nose piece up accurately
and you're working with bits of 1/4" and over.
OTOH, I don't often break 1/4" and I don't even wear them out that
fast. The ones I go through are 3mm - 5mm that I've snapped in half.
Sharpening those is from hard to impossible (if there's no length left).
work on one side at a time, obviously the same hand position on each. when
done the geometry on one side is the same as the other. When looking at the
very end you should see a straight line, the "peak" should divide the
geometry exactly, meaning both sides are the same. It needs the angle
measured co-axial from the peak through to the cutting edge, what 118 for
std material, and also some backard clearance, what 9 degrees. In practice
for most wood, if it looks good, and equal, alls well. The cutting lip
should be sharp along its entire path while spinning. Often easier by hand.
Machinery's Handbook tells you how to make the tooling after doing the
calculations for actually making all the geometry correct for something so
start with the cutting lip, and sort of spin and up-shove if using a
g-wheel. Its a minor movement. Google.. Actually I don't even know the
right procedure. I use anything handy- like a ut-off wheel on a dremel.
The geometry is gonna cut, or it ain't, precision ain't important for most.
Its freakin incredidble the physics and math that make it what it is to be
what it is though, cuting tools of any type.
I guess the point is, you can't use the drill press b/c of the stationary
stone, or whatever ,would need to cam in and out while following the flute
while spinning to sharpen. If you look a the construction of bit stock,
though, there is actually a land on the outer edge , so the outside
perimeter has clearance too.
Reading the DD manual helped out with understanding what it is doing.
The bit needs to be aligned in the 'chuck' The chuck has a cammed ring
that pivots the bit as you rotate it to create the relief angle.
Pretty neat idea.
I can only assume the grinding jig does something similar.
I'm gonna try Bill's method and see if I can get the hang of it before
I consider a DD.
There is a old trick I always use.... when there is no gage available
you can hold two HEX nuts side to side touching between your thumb and
forefinger for the right angle.( hold up to light with drillbit to
The Drill Doctor and the angle guide are almost certainly doing much
more than you think. Twist drills are deceptively complex.
Nope. Take a look at the tip of a fresh drill bit- in particular, the
fact that the tip is not pointy like a pencil.
You can sharpen them freehand on a belt sander or fine grinding wheel,
but it takes a little practice, and it really helps to have someone
show you how in person. I'll try to descibe it, but I don't know how
much it will help.
Basically, there are two huge things to worry about- The first is the
tip profile. It should look like a forward slash ( / ), and not a
point. The middle of the slash should cross the center of the bit.
The second is the "wing" angle. It should be 135* on most bits.
To get the profile right, you need to start grinding near the cutting
edge (be careful not to round it off), and rotate the bit until it has
ground that entire side. You can do this several times, but you're
not rotating the bit all the way around. Once you're happy with the
first side, lift the bit off the wheel, and rotate it 180* degrees,
and repeat the process until the tip profile is centered.
It takes a fair amount of practice, but it's not too tough once you
get the hang of it.
The drill sharpeners have an indexer to get the bit in the right
position, then lock it so that it is properly aligned with the cams.
As you twist the holder, it rides on cams to raise the bit
appropriately as it nears the back of the grind. Well worth the $$$
to get one if you've got a lot of bits to sharpen, IMO.
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 - firstname.lastname@example.org
Those various sized/shaped ceramic sticks available from
Garrett-Wade, etc., work quite well for hand sharpening smaller
sized drill bits.
Hold the bit upright in a vice and run a 600/800 grit flat
ceramic stick from the back of the flute towards the cutting lip.
Use the same pressure and number of strokes on both sides.
Repeat with finer grit ceramic sticks until you've got a good
Use a 1200 grit oval shaped ceramic stick to knock the burr off
the cutting lips. The oval shape allows it to fit into the flute
of small drill bits with less chance of creating a groove than
the edge of a half-round ceramic stick (learned the hard way).
I've been able use the ceramic sticks on drill bits down to about
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