Wednesday, January 21, 2009

Sharpening a Drawknife

The best advice I can give someone who is new to woodworking is: Learn to sharpen more than one way. Not all tools can be sharpened using the same method.

My personal preference is to sharpen chisels and plane blades with Japanese waterstones, carving chisels with a leather strop, gouges with a contoured leather strop or contoured felt wheel chucked in a grinder, moulding plane blades with slipstones, and carving knives with ceramic stones.

And there are more methods available than just these.

After hearing Mike Dunbar's presentation at the WIA Conference, I remembered an old drawknife I had purchased (and never sharpened) when I was new to woodworking. Following is how I sharpened this tool, but there are other ways to do it.*

First, sandpaper was used to remove the fine layer of rust that had covered the blade from sitting unused in my basement for 16 years.

A drawknife cannot easily be sharpened by holding the blade and moving it along a stone, as you would a plane bl ade. Instead, it's easier to keep the drawknife stationary and take the stone to it.

So, I used an 80 grit diamond stone to "scrub", in a circular pattern, the flat side of the blade. You can see the swirl marks in the photos.

Note: Please be careful with this sharpening technique. It's very easy to slip and cut yourself. (Don't ask me how I know this.)

A 600 grit ceramic stone followed the diamond stone, followed by an 1800 grit ceramic stone. I used ceramic stones because they cut quickly and are small & light, making them easy to hold. I would not use waterstones this way because the blade might gouge the stone.

The blade was very dull, so a circular motion was a fast way to remove steel. But I changed to carefully sliding the stones back and forth as the blade became sharp.

The same technique was used to sharpen the curved side of the blade, except that I was careful to maintain the shape of the convex bevel.

This drawknife can benefit from a little more sharpening to remove scratch marks, but I took it for a test drive anyhow. It worked great and rounded the edge of a piece of cherry effortlessly. And after 16 years, I'm finally able to put this fun-to-use handtool to the work it deserves.

*Mike Dunbar uses sandpaper wrapped around a block of wood to sharpen his drawknives.

10 comments:

Anonymous said...

Kari,
Thanks for the interesting post. I found Peter Galbert's blog very helpful regarding the care and feeding of the drawknife. He has a blog post from April '07 on this very subject (http://chairnotes.blogspot.com/2007/04/knife-grinding.html).

I found out the hard way that a sharp drawknife can be dangerous. You should only pick it up by its handles (duh).

Have you tried making a post & rung chair? It's a blast! You'll get good at drawknifing, that's for sure.

Tom Anderson-Brown

The Village Carpenter said...

Tom, thanks for the link! That's interesting that Peter puts a hollow grind on his drawknife. I have never made a post and rung chair but I sure am having a good time playing with this drawknife so maybe there is one in my future. : )

Chris Schwarz said...

Kari,

The drawknife is the most dangerous tool to sharpen.

Let's just say that Ohio's Workers' Comp system had to create a new "injury code" for me about 10 years ago because of a drawknife.

Chris

The Village Carpenter said...

Chris, I believe it! I think I was getting a little overconfident with my smooth moves and paid for it with a sliced finger.

Dan said...

Kari,

I’m glad your forlorn drawknife finally has a chance to shine! Watch out, they are addictive! Sorry about your finger - the good news is you'll probably never do that again.

I find them awkward to hold when sharpening, but here’s what works for me. For bevel shaping, I usually just use a file, with the drawknife clamped down at the edge of the bench. For honing, I use a Granfors Bruks axe stone (natural sandstone) and have had success with a modified "fiddle" grip - the near handle in the crook of my left arm, the far handle in my left hand, and the blade parallel to my forearm. I have also worked on it using my shavehorse to hold one end.

Have you tried some serious "hogging" with it yet? They can remove wood like you wouldn't believe! Have fun!

Woodbloke said...

Kari - good stuff on the draw knife, I used to have one but got rid of it years ago. Of course, now that you've got this tool working well, you'll need a decent a decent shavehorse...I see tht LN do a nice on for a mere trifling $650. Not that I have any intention of hastening your already lamentable slide down the 'Slope' you understand.... - Rob

Bob Rozaieski said...

Good rescue Kari! I love my drawknife. You'll find that they are spectacular for a lot of tasks, not just building chairs. I often use mine for tapering jobs. Nothing can taper a table leg as fast leaving very little cleanup for a long plane.

The Village Carpenter said...

I believe I can find all kinds of uses for this tool and wish I'd sharpened it up sooner! And Rob, I have "shaving horse" on my to-build list, but it might need to move closer to the top of the list now. ; )

Stephen Wilson said...

This method might not work for large drawknives, but for my 8" blade, I use a Tormek with the drawknife held in the (large) knife jig against the universal support and grinding into the edge. (Remove the leather stropping wheel as it gets in the way.) Grind a full concave bevel at around 25 degrees with light pressure at the end for the finest edge. Hone with an extra-fine ceramic or diamond slipstone. It is easy to hold this flat across the concave bevel created by the Tormek because it is supported on both sides. Remove the burr from the flat side of the knife with the same slipstone and a swirling action. This has produced a razor-edge that is easy to maintain before you have to go back to the grinder.

The Village Carpenter said...

Thank you, Stephen, and everyone for offering your sharpening techniques!