How can I properly sharpen my knives with power tools?

Question

I have drawers full of knives and blades that have never been as sharp as when they came from the factory. I have some whetstones, Lansky sharpeners, and leather strops. I have tried to use those but eventually realized that I'm as likely to make an edge worse as I am to improve it. In large part this is because:

• I can't maintain a proper and constant angle of attack while working a curved blade across a series of stones by hand.
• I don't know which step to use or for how long, given a blade's condition.

Meanwhile, I have benches full of power tools: Bench grinders, belt sanders, drill press. I believe I can hold a reasonably constant angle while dragging a blade once or twice across a tool that's doing the work for me.

As I understand it, there are only three steps to producing a perfect edge:

1. Sharpen: In this step the blade is run against the grit to grind a new edge. Perhaps two grits (usually 100 and 400) are used in this step. (Optionally, one might grind a relief angle that's more shallow than the cutting edge angle, but it's the latter one that has to be maintained going forward.)
2. Hone: Here the blade is run with the grit to knock off burrs and nudge dings back in line. Power honing is done with finer grits, but not sure how fine.
3. Strop/polish: Once again the blade is run with the grit to smooth the edge. You know you're done when the edge is as shiny as a mirror.

With this in mind I began searching for sharpening wheels preloaded with an appropriate compound for each step. Instead I've found a smorgasbord of wheels ranging from glass to paper, and separate polishing compounds of widely varying composition, many of which users report needing to supplement with oil and wax. Great. Am I missing a shortcut around selecting and loading the power sharpening tools?

Now, suppose I manage to find or prepare a line of 3 or 4 powered wheels. I pick up a knife. How do I know which step to start at? And how do I know when I'm ready to move it to the next step? I know that if I do it right then at the end I have a blade that will catch and slice cleanly through a loose sheet of newsprint. But is there a foolproof way to get there without grinding away undue amounts of time and metal?

Answer 1

The power tools are really only useful for putting the initial bevel on the edge or significantly changing the bevel angle. In my usage they are much more aggressive than you would expect and make any fine sharpening quite difficult (for me at least). One useful thing about the grinding wheel is that it will give you a hollow grind, making it a lot easier to use a sharpening stone (since the hollowness of the bevel sort of locks it in place at a fixed angle as you run it along the stone -- hard to explain but it makes sense when you feel it).

You can tell if you would save a lot of time using the grinding wheel by simply examining the bevel. Look at how the two edges come together to form the cutting edge.

If this is all bent and broken, or round, then you would save a lot of time by grinding a V shape bevel on. Or if you want to significantly change the cutting angle (generally the thinner the cutting angle the sharper but also more fragile the cutting edge will be). Otherwise stick to the stone.

In regards to your tendency to roll the blade: it happens. Until you get more comfortable always keep the knife at a less aggressive angle than you would expect (since you already know you have the propensity to roll the blade). Use a sharpie on the bevel as and check it often / reapply as you are using the stone.

Another thing you mention was when to move up to the higher grit stones. Pretty much just check for the burr on the opposite side that you are working with your fingernail. Until you get a burr keep on the lower grit stones. Once you get a burr, put sharpie over the entire bevel. Now move up a grit until all the sharpie is gone. Repeat for each higher grit, then strop it on leather with compound.

For your concave blades I find that it is actually a lot harder than you might think to grind it on a wheel without biting into the edges. Instead I prefer the crock sticks (Lansky turn box) to sharpen followed by a strop. Or a drum stick wrapped in 600 grit sandpaper.

It is really not so hard to learn and gives a lot of enjoyment. But the grinding wheel is a great time saver for grinding out any deep nicks or dings.

Answer 2

Forget the power tools. That's like killing a mosquito with a shotgun. Check out Paul Sellers' video on sharpening a kitchen knife (https://www.youtube.com/watch?v=bailuQUh2mY), then go get yourself 2 or 3 of the little diamond sharpening paddles he recommends. Works great, my knives are nice and sharp, and it's convenient: I keep my paddles and my spacer block (you'll know what I mean when you watch the video) right by my knife storage block.