Sharpening moulding plane irons

[Chris Atzinger]

Hi,

I need to sharpen some irons from a mixed set of moulding planes (hollows and rounds only, at the moment). For chisels and plane irons, I use shaptons with a honing guide.

How do I sharpen these old irons that are rounded or their counter parts that are concaved (is that the right word here? I am talking about the irons for making beads.).

Any guidance would be greatly appreciated!

Thanks!
Chris

[paul cottingham]

I just flatten the backs for the most part, I am afraid of screwing up the profile if I use a slipstone on it.

[Jim Koepke]

How do I sharpen these old irons that are rounded or their counter parts that are concaved (is that the right word here? I am talking about the irons for making beads.).

One way to remember this is to think of a cave going inward as does concave. Convex is out. My problem is remembering the planes are named for what they leave. So a hollow(ing) plane has a convex blade and a round(ing) plane has a concave blade. No wonder it is confusing.

Well that is if I haven't gotten it backwards.

EDIT


Well, to add to the confusion, hollow and round planes are named for their soles, not the profile they leave behind, so a "round" leaves a cove (concave) profile, while a "hollow" leaves a scotia (convex) profile. All other molding planes are named for the profile they leave behind, so an "astragal" actually cuts an astragal, an ogee leaves behind an ogee (not a reverse ogee, which is the opposite for this plane), and a bead leaves behind a bead.


Oops... Looks like I did get it backwards.

Thanks David.

End Edit

One way to do this is to flatten the back of the blade. This will usually help it to cut somewhat better. Use this to cut the profile in a piece of wood. Adhere some abrasive paper to this. For this my choice is to start with about 200 grit. If you go much coarser the thickness of the paper can distort the profile. After this, cut another profile in a piece of wood. Check it against the plane's profile and adjust as needed. Adhere a finer grit of abrasive to this.

Repeat as needed until you have reached as fine of a grit as you desire.

Once a blade is in pretty good shape it is fairly easy to strop them or freehand on stones. I try to sharpen my blades before they need something coarser than an 8000 or 4000 stone freehand and then strop on leather charged with a green stick.

If the blade is stropped before getting too dull it can keep the blade working longer between sharpenings.

I also do this with gouges and carving tools.

For beading blades I will use slip stones especially on the smaller sizes. On beading blades that need rehab a dowel with abrasive paper helps until you can cut a profile small enough to not open the blade too much.

jtk

[jamie shard]

I >highly< recommend this video. It will teach you everything you need to know and you'll get the visual sense of how to do it:

Sharpening Profiled Hand Tools
Larry Williams

Sharpening
hand tools with profiled edges can be a challenge. Larry Williams has years of
experience and shares it here, showing how he handles sharpening various molding
plane blades, and other specialized tools that often are not sharpened correctly
or well.

92 Minutes, DVD. Lie-Nielsen Toolworks Productions, 2009.

[David Keller NC]

One way to remember this is to think of a cave going inward as does concave. Convex is out. My problem is remembering the planes are named for what they leave. So a hollow(ing) plane has a convex blade and a round(ing) plane has a concave blade. No wonder it is confusing.

Well, to add to the confusion, hollow and round planes are named for their soles, not the profile they leave behind, so a "round" leaves a cove (concave) profile, while a "hollow" leaves a scotia (convex) profile. All other molding planes are named for the profile they leave behind, so an "astragal" actually cuts an astragal, an ogee leaves behind an ogee (not a reverse ogee, which is the opposite for this plane), and a bead leaves behind a bead.



One way to do this is to flatten the back of the blade. This will usually help it to cut somewhat better. Use this to cut the profile in a piece of wood. Adhere some abrasive paper to this. For this my choice is to start with about 200 grit. If you go much coarser the thickness of the paper can distort the profile. After this, cut another profile in a piece of wood. Check it against the plane's profile and adjust as needed. Adhere a finer grit of abrasive to this.


Chris - Jim's given you some fine advice here; the only thing to realize is that the plane actually has to be able to cut to act on this advice. If that's not the case, here's the definitive way to profile the irons so that the plane will cut:

1) First ensure that the plane is straight front to back (i.e., it's not warped to the left or to the right). Small discrepancies can be fixed by removing a bit of wood from the offending side of the sole with a small block plane, some sandpaper, or a rasp or coarse file. Then check to see that the depth of the sole is consistent from the front (toe) to back (heel) of the plane. If it rocks when it's set down sole-first on a flat surface, you can still make the plane work fairly well if the difference is fairly small (less than 1/16"). If the toe and heel contact the flat surface but the portion of the plane where the blade is (mouth) does not, then you will have to re-shape and re-profile the sole, which is a bit beyond the scope of your question.

2) Remove the wedge of the plane. If it's stuck, the best way to do this is to strike the heel of the plane sharply with a dead-blow hammer (preferred) or a wooden mallet when it is held upside-down. If that doesn't do it, and the plane is a manufactured one (not an unmarked craftsman made one, which typically have untapered blades), then carefully drive the blade out of the mouth of the plane by tapping on the top part of the blade (the tang) with a brass hammer. Because both blade and wedge are tapered, driving the blde out through the mouth will automatically loosen the whole assembly. Don't grip the plane upside-down by the wedge in a vise and attempt to drive the body off of the blade/wedge. I see this advice often, and unless you're quite good and quite careful, you're likely to snap the finial off of the wedge and bugger up the top surface of the plane.

3) Remove the iron and polish the back with a bit of 400 grit sandpaper, being careful not to round over the cutting edge. All you are trying to do here is make a scratched line visible.

4) Put the blade back into the plane, and position it so that at least a little of all portions of the cutting edge is just barely peeking above the sole when you sight down the length of the plane. Place a shim (could be almost anything - commercial wooden shims that come from the home center works well, as does a section of a post-it note pad) behind the blade (between the blade and the back of the mouth) so that it wedges the blade against the front of the mouth.

5) Using a scratch awl, carefully scribe the profile of the front sole of the plane onto the back of the iron.

6) Remove the blade, and using one of many solutions to profile and hone a curved blade, establish a bevel and cutting edge that matches this scribed profile accurately. There are many potential tools to accomplish this. Since I'm a carver and have to sharpen these sorts of blades regularly, I use DMT diamond hones, followed by slip stones, and finally a strop made by coating several sizes of wooden dowels with honing compound. If you don't have either slip stones, diamond hones, or ceramic files, the easiest route is to buy some spray contact adhesive (3M #77 is a good one that is sold in home centers) and glue some 400 grit, 800 grit and 1200 grit wet-dry sandpaper to various sizes of wooden dowels. You will also need to strop a surface left behind by the 1200 grit sandpaper - you want a molding plane iron just as sharp as bench plane blade or a carving tool.

7) Once you have the bevel and cutting edge shaped to the profile of the sole, and have honed the bevel so that a burr is raised on the back of the blade all along the cutting profile, evaluate whether you can simply flatten the back a little to remove the burr and finish the job. Often, you will have to remove an extreme amount of metal to do this, so the alternative is simply to strop the back of the cutting edge very slightly to remove the burr. It is very important that you do this at as low an angle to the back as absolutely possible - many old molding planes have a sharp bevel on the back as busy craftsmen simply filed a small back bevel to get the plane back to "working dull", and as this was done, that back bevel gets steeper and steeper, and eventually the whole blade profile must be ground/profiled/honed to bring the plane back to effectiveness (otherwise, it's just a fancy curved scraper!)

[Ryan Baker]

I >highly< recommend this video. It will teach you everything you need to know and you'll get the visual sense of how to do it:

Sharpening Profiled Hand Tools
Larry Williams

Sharpening
hand tools with profiled edges can be a challenge. Larry Williams has years of
experience and shares it here, showing how he handles sharpening various molding
plane blades, and other specialized tools that often are not sharpened correctly
or well.

92 Minutes, DVD. Lie-Nielsen Toolworks Productions, 2009.

+1. That's a great video.

[Joe Fabbri]

I think a "scotia" is a type of cove (made I think with a side round), which might be making things confusing.

The round makes a cove (or cavetto) and the hollow makes an round over/quarter round (or ovolo), I believe. That's correct, right guys?

[David Keller NC]

I think a "scotia" is a type of cove (made I think with a side round), which might be making things confusing.

Yep, sorry about that - I was thinking of a torus, not a scotia, which is indeed a form of cavetto (usually an eliptical cavetto)


The round makes a cove (or cavetto) and the hollow makes an round over/quarter round (or ovolo), I believe. That's correct, right guys?
Yes, that's correct - the hollow can make a quarter round or a nose (a completely rounded over edge of a board) depending on how it's manipulated.