Sharpening Curved Blades

 

Sharpening Curved Blades

"A promise is a promise,"  Call said. "A promise is words-a son is a life," Clara said.

Lonesome Dove, Larry McMurtry 

So a couple things. First off I just finished Lonesome Dove and all I can say is wow. An absolutely amazing book Larry McMurtry is a true master. 

The second thing is the post that follows was supposed to be published by Fine Woodworking but then covid happened then the editors changed then they evidently published a similar article by a much better known builder/author and mine got scuttled which was disappointing but life goes on.  the double spaced text below is from the original proposal then the regular centered text if mine from today. 

Sharpening curved blades

When I started building Windsor chairs after years of building mostly square

pieces (dressers, blanket chests and the like) I realized that one of the biggest

challenges was learning how to sharpen tools with curved blades like scorps (in

shaves), compass planes, heel shaves and the like.

Initially I read all the books and did what they instructed, which was mostly

automotive sandpaper wrapped around dowels or pipes of roughly the same size

or free hand paddles on the face. I was used to sharpening straight blades like

plane irons or chisels using a couple different jigs and waterstones for fast,

consistent results. I heard once that sharpening without a jig is like shooting a rifle

without sights. You do occasionally hit what you’re aiming at, but it’s literally hit

and miss. So, after years using dowels and sandpaper freehand on my curved

blades with slow inconsistent results, I decided to apply the rational of jigs to

curved blades. The result is a fast, consistent, repeatable way to sharpen curved

blades in the same way that my various jigs sharpened straight blades.

Over the course of a couple years I was able to develop jigs, holders and methods

that allow repeatable and safe ways to sharpen everything from scorps to

travishers to carving tools in ways that are fast, safe and repeatable.

Tool that makes this all work is this strip sander from Lee Valley. I had this for a few years and used it solely to sharpen kitchen knives. The problem is the table only goes to 90 degrees and in order to sharpen scorps or travisher blades it needed to go past 90 sometimes way past 90. So when I looked at sharpening the scorp I came up with a simple pine (or whatever wood) block clamped to the top of the table. Then by tipping the table towards me, the block of wood became the new "tool rest" and then I could hit any angle I needed. Later I added the plywood top that makes the rest bigger and also aids in clamping it on. I may someday bolt it on to avoid clamps.  One important note is I removed the back platen which allows the strip to flex on the curved blade. 

The above pic shows how the Lee Valley strip sander without the wooden block lands at 90 (actually mine lands at like 5 degrees short of 90) and thus renders it useless for the scorp. 

Here you can see the block clamped on the aluminum table (or tool rest) and rolled back to 10 (or 80) degrees using a bevel gauge.

The below picture shows how the sanding strip now rubs perfectly on the bevel of the scorp. 

You can also use the same setup to sharpen travisher blades (the pieces of wood used to hold the blade idea I got from Pete Galbert). The blades are fastened to the block of wood with small wood screws and the pieces of wood matches the arc of whatever travisher you're using. This is a fairly flat travisher I built awhile back. 

The blade is screwed to the wooden holder and passed over the sanding strip. I usually go from a 400 grit belt and end with a 9u which I think is around 1500 which is razor sharp. 

Then is put the blade on the other end of the holder and turn the burr off and it is absolutely razor sharp. 

Here you can see how by using a marker it left just a whisper of the hollow grind. I get my strips from sharpeningsupplies.com and keep them hanging next to the sander which has a permanent spot on the bench. I usually start with a 600 grit and end at 6u. The last 2 pictures show the motor and switch setup for the sander. And yes I still use it to sharpen kitchen knives. 

Scrub Plane out of Firewood

 

Long is the way, and hard, that out of Hell leads to light

Milton., Paradise Lost

So first off this is my first post is a long, long time. I had a couple management jobs away from woodworking and chairs the kept me busy and frankly life has been really busy. But like Longfellow said, don't tell me your busy, ants are busy, tell me what you're about. It's also funny (funny weird not funny ha ha) how a non emotion, an adverb, has become the go to answer for how we are. 

As you can see I can still tangent. So yeah a couple jobs and other life stuff but I did recently get a really nice order and am setting up a shop which I will post about in the coming weeks. My current bill payer is carpentry which well pays the bills. Nothing more. 

Below you can see a handplane, specifically a scrub plane, that I made a while back. I could have bought one but this a really simple,  really forgiving introduction into plane making. The body is ash (made like a sandwich) and the front tote is ash as well.  All the wood came from a very well seasoned piece of firewood. 

It's sitting next to a Lie-Nielsen #5 for size comparison. The iron (also from L-N) is held in place with a pin and wedge which holds is tight enough. I do get pretty aggressive with this plane and the blade has come loose but that's a sign to me to settle down not a failure on the part of the plane. 

Here is a view of the cambered blade and wide open mouth. 

I don't lavish a lot of sanding on my shop tools or fixtures and this plane is no different. I barely sanded the bandsaw marks off and the finish is just wax but it does work really well. One thing that flies in the face of conventional plane wisdom is despite being a very light plane it cuts remarkably well. It's not a show pony more like an old pickup. If you want the plans I'd be happy to draw the shape and email them to you.