Sharpening A Curved Plane Iron

[Julie Moriarty]

I have a L-N 100-1/2 and the iron needs sharpening. I took it to a flat wetstone and had a bear of a time getting anywhere. I wanted to make sure I didn't lose the original curvature so I proceeded carefully. I just couldn't seem to get anywhere. It's tiny and difficult to hold or to get any kind of feel when seating it flat against the stone. Even attempts at putting on a secondary bevel failed.

Do I need to buy a curved stone or is there a way to sharpen it on a flat stone?

[Robert Engel]

There are videos out there on sharpening a cambered iron. Here (https://www.youtube.com/watch?v=lAq3hgSRVKM) is one.

Maybe a little holding fixture will help similar to a spoke shave.

[bridger berdel]

The waterstone may be helpful for lapping the flat side, but for the bevel you will probably have better luck using something harder. Its a small blade, so a small oilstone should be fine, if you are buying gear just to sharpen this one blade. I'm a freehand sharpener, so I'm used to working without a jig and curved, small blades are particularly difficult to jig anyway. If you need better grip on the blade you can make a handle by slotting a kerf in a block of wood that the blade just snugly fits into, shaping it to clear the bevel and fit comfortably in your hand and tighten with a wood screw.

[Jim Koepke]

As Bridger mentions, an oil stone may be better for sharpening curved blades.

Often my stone is set side ways and the sharpening is done side to side on round edged blades. If you get into hollow shaped blades, you will need a slip stone.

If you have a pair of vise grips it might make it easier. You may want to put some masking tape or thin pieces of wood on the jaws to keep from marking the blade.

jtk

[Nicholas Lawrence]

I have a stanley No. 40 (scrub plane) with a heavily curved blade. What works for me is using the blade to plane a piece of scrap pine (making a hollow the exact shape of the blade) and then putting a piece of sandpaper in the hollow. I just cut the sandpaper a little longer than the piece of scrap and staple it at the ends, but I suppose you could also glue it or something. Then I put the blade in my vise and use the sandpaper/scrap contraption to sharpen the bevel side of the blade. Once I have a good wire edge on the back side, I use a regular stone to remove it.

Nick

[Pat Barry]

I have a L-N 100-1/2 and the iron needs sharpening. I took it to a flat wetstone and had a bear of a time getting anywhere. I wanted to make sure I didn't lose the original curvature so I proceeded carefully. I just couldn't seem to get anywhere. It's tiny and difficult to hold or to get any kind of feel when seating it flat against the stone. Even attempts at putting on a secondary bevel failed.

Do I need to buy a curved stone or is there a way to sharpen it on a flat stone?
They provide suggestions on sharpening this little beast on their website. Look up the tool and look under the Use tab of the information they provide.

[Jim Koepke]

I have a stanley No. 40 (scrub plane) with a heavily curved blade. What works for me is using the blade to plane a piece of scrap pine (making a hollow the exact shape of the blade) and then putting a piece of sandpaper in the hollow. I just cut the sandpaper a little longer than the piece of scrap and staple it at the ends, but I suppose you could also glue it or something. Then I put the blade in my vise and use the sandpaper/scrap contraption to sharpen the bevel side of the blade. Once I have a good wire edge on the back side, I use a regular stone to remove it.

Nick

This technique has worked for me with many different gouges and blades. Almost forgot about it since acquiring a bunch of oilstones.

jtk

[paul cottingham]

I often sharpen cambers by putting the blade in a vise, then using a slipstone. If it is a regular plane iron, i put it in my eclipse, and pressure the ends first for a bunch of strokes, then closer in, etc.

[Pat Barry]

This technique has worked for me with many different gouges and blades. Almost forgot about it since acquiring a bunch of oilstones.

jtk

This is similar to the technique recommended by LN

[Stephen Clement]

You could try a method used for moulding planes. Lay masking tape on the sole of you plane. Extend your blade so it just peaks above the taped sole. Run a file across the sole until the blade has a small flat across the length. Be careful not to cut through the masking tape. Now remove the blade from the plane and hand hone the edge until the flat just goes away. This is best done with the blade held in a vise and the stone in hand. I use the small diamond paddles. Then finish on a strop.

[Tom M King]

It'll sharpen fine on a flat waterstone. A figure eight motion can do it as the edge needs to be rolled along as it's pushed. Don't push down so hard to start with until you learn the motion, or the edge might dig into the stone. I have an old Record guide that has about a half inch ball as the roller that I use when I'm tired. It has a big thumb screw that tightens a flat end on the bolt down on the top of the iron.

edited to add: I just looked at that plane online, and the iron has a 3" radius to match the sole curvature. I think my Record guide would work for that, but I can sharpen it by hand if not. If you can't figure out how to do it, send it to me, and I'll sharpen it for you. If should cut Balsa for a LONG time once it's good and sharp.

since we can't post a link here, do a search on ebay for "record honing guide", and there will probably be one for sale. There's one currently on there that is similar to mine. Mine works on my ECE scrub plane iron, so it should work on that LN one.

[Patrick Chase]

I have a L-N 100-1/2 and the iron needs sharpening. I took it to a flat wetstone and had a bear of a time getting anywhere. I wanted to make sure I didn't lose the original curvature so I proceeded carefully. I just couldn't seem to get anywhere. It's tiny and difficult to hold or to get any kind of feel when seating it flat against the stone. Even attempts at putting on a secondary bevel failed.

Do I need to buy a curved stone or is there a way to sharpen it on a flat stone?

Here's what I do (though note that this is a grinder-based workflow):

1. Paint the back of the blade with marking fluid (it comes off with alcohol) and scribe the radius you want, probably from a template of some sort.

2. Grind back to the scribed line from 1 at 90 deg (i.e. grinding wheel perpendicular to blade). This will create a blunt edge of the correct radius. The reason for doing this is to avoid problems with heat buildup in a thin edge for as long as possible.

3. Set tool rest to the desired primary/hollow bevel angle, and grind freehand until the blunt edge is almost-but-not-quite sharpened to a point.

4. Grind your desired secondary bevel by hand. I use an Eclipse-style guide that's been "customized" (by filing away metal from the outside edges of the 2 axle supports) to allow it to tip further to each side

You can also grind the entire primary on stones, but that's typically slow going because you can only grind one "spot" at a time and because you'll need to remove a lot of material if you actually want to change radii.

[Pat Barry]

Here's what I do (though note that this is a grinder-based workflow):

1. Paint the back of the blade with marking fluid (it comes off with alcohol) and scribe the radius you want, probably from a template of some sort.

2. Grind back to the scribed line from 1 at 90 deg (i.e. grinding wheel perpendicular to blade). This will create a blunt edge of the correct radius. The reason for doing this is to avoid problems with heat buildup in a thin edge for as long as possible.

3. Set tool rest to the desired primary/hollow bevel angle, and grind freehand until the blunt edge is almost-but-not-quite sharpened to a point.

4. Grind your desired secondary bevel by hand. I use an Eclipse-style guide that's been "customized" (by filing away metal from the outside edges of the 2 axle supports) to allow it to tip further to each side

You can also grind the entire primary on stones, but that's typically slow going because you can only grind one "spot" at a time and because you'll need to remove a lot of material if you actually want to change radii.
This ^^^ is not the answer to the OP's question.

The following is directly from Lie Nielson "
Blade Sharpening

The blade comes ready to use. Additional honing will improve performance. For honing: One method is to plane a groove in softwood with the blade set for a coarse cut. Charge the resulting groove with honing compound and hone the blade by pulling backwards through the groove. Another method is to shape a groove in a spare or broken waterstone with a 7/8" dowel wrapped with coarse (60-100 grit) sandpaper. Hone the blade by pulling through the groove. For grinding: Re-grind as necessary, following the original bevel angle and radius as closely as possible. Marking the bevel with a felt marker will help you see what you are doing.
"

[Patrick Chase]

This ^^^ is not the answer to the OP's question.

The following is directly from Lie Nielson "
Blade Sharpening

The blade comes ready to use. Additional honing will improve performance. For honing: One method is to plane a groove in softwood with the blade set for a coarse cut. Charge the resulting groove with honing compound and hone the blade by pulling backwards through the groove. Another method is to shape a groove in a spare or broken waterstone with a 7/8" dowel wrapped with coarse (60-100 grit) sandpaper. Hone the blade by pulling through the groove. For grinding: Re-grind as necessary, following the original bevel angle and radius as closely as possible. Marking the bevel with a felt marker will help you see what you are doing.
"

The problem with the old hone-in-the-groove approach is that it doesn't actually work very well because the radii don't match. Put another way, the track cut by the blade is only the same radius as the blade face if the bevel angle is the same as the bed angle, and if that's the case then you'll have much bigger problems (as in: it won't cut because the clearance angle is 0).

I use a variation on that approach with concave spokeshaves, but in that case I fabricated a honing surface at the true radius of the bevel face, not the cut radius (of course if I were being really nit-picky I'd point out that a circular bevel face actually cuts an elliptical groove and vice-versa).

[Julie Moriarty]

Thank you for the replies. After reading them all, I now have something to go on. I looked for L-N videos earlier but couldn't find any. Thank you, Robert, for the link.

L-N says the plane is ready for use. I own several L-N planes and the enthusiasm to use them always has me taking them immediately out of the box and finding some wood to reduce in size. All the previous planes have worked right out of the box. Not so with this one. Mostly, all I could get was sawdust. Granted is was cheap balsa and maybe that was the problem. But I will use it on hardwoods once I have the shop set up again.

I liked the idea of holding the iron in place and curving a stone around it. You can see what you're doing. When you are trying to hone it free hand, you can't see a thing, at least not from above.

[Jim Koepke]

When you are trying to hone it free hand, you can't see a thing, at least not from above.

Often when a non-straight blade is being sharpened one of my hands is holding a small stone and the other is holding the blade. Both are held so the edge can be seen. This is done outside in the sun for the best lighting if possible.

jtk

[Patrick Chase]

The problem with the old hone-in-the-groove approach is that it doesn't actually work very well because the radii don't match. Put another way, the track cut by the blade is only the same radius as the blade face if the bevel angle is the same as the bed angle, and if that's the case then you'll have much bigger problems (as in: it won't cut because the clearance angle is 0).

I use a variation on that approach with concave spokeshaves, but in that case I fabricated a honing surface at the true radius of the bevel face, not the cut radius (of course if I were being really nit-picky I'd point out that a circular bevel face actually cuts an elliptical groove and vice-versa).

Expanding a bit: The approach that has worked the best of all for me was the following:

1. I created a template at the true radius of the spokeshave's primary bevel by sanding it until it matched. The template here is "opposite gender" to the blade, i.e. convex template for a concave blade.

2. I used the template to create a form with the same (concave) radius as the blade. I then stuck some of the cheap iWood diamond tape that Stu sells on that form (I also stuck a chunk of the diamond tape to the template so that it's thickness would be included when creating the form).

3. I use the diamond-coated form to dress the surface of appropriately sized waterstone chunks (harvested from old mostly-worn-out stones that I've retired from normal use).

Et voila, custom slipstones with the right radius.

This approach isn't worth the effort for ordinary cambered plane irons since it's so easy to shape those on a grinder and hone either freehand or using a tip-able guide like the Eclipse. Also I use too many different radii (3", 4", 6", 12", 16" in use right now) for that to be practical.