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Knife Sharpener

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Our kitchen knives are several years old and weren't holding an edge as well as they did when new. Our knife sharpening steel was seeing much more frequent use than it did when the knives were new. So, I looked around on the net and found the Lansky knife sharpener had a good reputation. The price - $60 or more - seemed high given the simplicity of the unit. I already had some diamond hone blocks from Harbor Freight in my shop so all it took is a little time and some scrap to make my own knife sharpener using the Lansky idea - the concept is essentially the same as used to make jigs for sharpening lathe bits: grind steel at a reproducible angle.

The hone blocks are metal with the diamonds embedded (in metal) on the surface. They are backed by a plastic block 6" x 2" x 0.115". A piece of 1/2" rod 0.015 shorter than the plastic block's width was milled along its length, depth 0.100 to form a flat. Drilled and tapped both ends 8-32 and made 1/8" thick washers from the same 1/2" round for each end, thus making a clamp to grip the sides of the honing blocks. Gripped this clamp in the mill vise with the flat against the jaw, then drilled and tapped a 10-32 hole at the center for the guide bar; this hole was 1/4" from where the round side contacted the jaw so it is closer to the flat. A 12" long piece of 3/16" rod was threaded 10-32 for 1/4" and threaded into the clamp.

Initially I planned to grip the ends of the clamp while sharpening knives. In practice this seemed unsafe so I added the little vertical handle on the clamp. Just a piece of 1/2" rod drilled to pass the 8-32 socket head screw that secures it to the clamp. The end was made concave by profiling it with the side of a 1/2" end mill so it fits nicely onto the clamp. The handle is a little off center so its securing screw doesn't damage the threads of the guide rod.

The wood for the large section is oak from a dead Nordic-Trac, two pieces screwed together for a thickness of 1.5" (helpful to avoid contacting the surface the sharpener is used on [since diamond scratches everything]). The rebate along the end is 0.45" by 0.11"; knives are positioned against this for sharpening. A bit of 1/8" Plexiglas scrap is used as a clamp to secure the knife with a rubber band looped under it to provide some pressure and friction. In use I slide the knife tip in from the side while holding pressure against the rebate.

The angle guide is milled on both sides for 1" to provide a rectangular flat section; my flat is 1/8" thick but thinner would be easier to file to pass the guide rod. Two holes were drilled 1/4" apart in this flat, size to easily pass the guide rod, then the material between these holes was filed away to form a short slot. A little more filing is needed to allow vertical movement of the guide rod (this can be done later by holding the part in a bench vise). A hole was drilled parallel to the flat section and 1/4" from the flat. Once this was done it was parted off 1/4" from this hole, then the end was drilled and tapped 8-32 to complete the angle guide.

The small wood block holds the vertical rod. This rod is 3/16" diameter by 5.5" long and is about 5" from the rebate. I drilled the hole in the wood block to hold the rod a few thou under size and pressed the rod in expecting it to grip well. Unfortunately, it allowed the rod to pivot from force on the angle guide so I had to add an 8-32 x 1/2" screw in the side of the block to prevent this. The goal is to have the guide rod in the center of the unit's width so place the hole for the vertical rod appropriately accounting for the angle guide's offset. All of the adjustments are via 8-32 socket head screws so a hole was added in the wood block to hold the Allen wrench for these screws.

A short section of line printer rod was drilled to fit over the vertical rod. Length was adjusted so the angle of the guide rod was 20 degrees when the angle guide is sitting directly on this section. The angle guide can be raised to achieve larger angles. Lansky allows several angles between 17 and 30 degrees but our kitchen knives all seem to work well with a 20 degree bevel so I haven't tried other angles.

Using the Knife Sharpener

Place the sharpener on a flat surface preferably with a cloth under it to prevent it from sliding in use and also to avoid scratching the flat surface from inadvertent contact with the diamond hone. The sharpener should be near the edge of the flat surface so the hone will be able to make a full stroke while maintaining contact with the knife blade. Clamp one of the hones to the guide bar with about an inch projecting beyond the clamp; the upper end of the hone should rest against the guide bar - see the picture at the top of this page. Pass the end of the guide bar through the hole in the angle guide.

The bevel on working knives gets rounded over time as they are touched up with a sharpening steel. This sharpener restores the bevel. To do this the knife is installed in the sharpener by sliding it, tip first, under the clamp on the end of the unit while keeping the back of the knife against the rebate. Slide the knife along until the mid point of the blade is at the mid point of the sharpener. This will allow the guide rod to move approximately equal distances left and right during sharpening. Depending on the blade thickness, the rubber band thickness, and how the clamp is set up the blade may not be secure in the unit -- in this situation the knife can be stabilized by using the knife handle to hold it against the rebate.

With the knife clamped to the unit, starting at one end of the blade, lift the hone away from the blade, move the hone toward the angle guide until the bottom of the hone is near the edge of the blade and bring the hone down to contact the blade. Put light downward pressure on the hone and pull it toward you until the top end of the hone nears the edge of the blade. Lift the hone slightly, move it toward the angle guide again, move the hone laterally along the blade, put light downward pressure, etc. Repeat for a couple passes, then turn the knife around and do the same thing to the other side. Remove the knife from the sharpener and examine the bevel - if the bevel is narrower on one side than the other then make a pass or two on the narrower side to even things up. Once you have well defined, same size bevels on both sides the knife is sharp. Change to the finer grit if desired and make a pass or two - once the bevels are established using the coarse or medium grit it doesn't take much to refine them with the fine grit. I've tried all the grits and don't see a difference in knives sharpened with medium or fine... but fine does cut slower.

NOTE: My Harbor Freight diamond hones are about 10 years old so the metal separated from the plastic on one. I glued it back on and it seems to be fine.

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