In my Make a Panel-raising Plane article in the November 2013 issue of Magazine, the iron I use came from my reserve of New, Old Stock (NOS) irons. These irons were manufactured in England from around WWII. Each iron is tapered, and of laminated construction the tool-steel cutting edge is forge-welded to the face of the iron body. The irons are not cut, meaning there is no slot for attachment of a cap iron. They are very traditional in that respect. Iron is already tempered so it is important to keep that temper when the cutting edge is formed. You can find a blade that is similar to mine at Hock Tools, even if you don’t have any NOS blades.
Before any cutting-edge shaping begins, the iron is ground along the long edges to an angle matching the cheek angles of the plane, which are about 23. That means the left edge is acute and the right edge is obtuse. I also make sure the iron is parallel over its length, or possibly slightly tapered away from the cutting edge.
When the iron is shaped, it has three beveled edges. A short bevel on the right edge defines the fillet, the long bevel in the middle defines the angled face of the panel and the somewhat shorter bevel on the left defines the tongue that fits into the door or lid frame. The fillet bevel is a side bevel and is quite steep, generating more of a scraping action than a cutting action. Sharpening this edge to a typical acute angle of 25 or so would give a bevel that is wide and thin and weak in terms of the type of cutting it does. The other two bevels are arrayed more on the leading edge of the iron and are sharpened to a standard bevel (25 30) since they cut in the typical manner (slicing and levering).
I dont actually measure the bevel angles of the iron as I hone them, but judge them by eye. A bevel should be slightly wider than the thickness of the iron at its cutting edge for cutting or slicing. This means that the bevel angle should be between 25-30 degrees. The thickness of the iron at this point could affect the width of the fillet, or it could be slightly less. I use an angle between 45-70.
The first step in shaping the iron is to paint the face (the tool steel surface) with layout fluid. I use Dykem Steel Red Layout Fluid (www.mcmaster-carr.com). This is basically a red dye with an alcohol base. After drying the dye, place the iron in the plane and then set it with the wedge.
Move the iron forward, so that it reaches its full width. To scribe the profile of the plane onto the iron, use a long, thin awl. Make sure to keep the awl flat on the iron. Make one scribe mark for each face of the profile. Take the iron off the plane and clean up the marks.
A lot of material needs to be removed from the cutting end of these irons. I use a 3 cm-wide Norton 36 grit SG wheel (blue). The tool rest is set square to the wheel so I am grinding a very blunt edge to the iron. As I go through this huge step, the chances of losing my temper are reduced. Cool the iron every couple of passes across the stone, and dress the stone on occasion to remove glazing, etc and improve the cutting action.
Grind the two long edges close to the line, but do not grind the fillet edge just yet. The iron’s length will be reduced if the long edges are ground. The iron’s width is reduced when the fillet edges are ground. If you cut the fillet edge to size too soon and make the iron undersized youll have to grind away a lot of iron to recover. The long edges require more care so they should be done first, while the fillet edge is very short and should be done last.
These scribe lines are only a guide. As I get close to the lines, I begin to grind the iron to the precise shape using my eye as the guide.
To check my progress, I hold the iron firmly to the bed with my thumb with the plane upside down and the toe facing to me. The iron is then advanced to just above the sole, keeping the iron centered on the bed. The face of the iron is red from the layout fluid, but the newly ground, blunt edge is shiny. Take care to only judge the iron profile from the red face. The fillet edge can be ground to close to its final dimension, but leave it fat (at least 1/16 shy of the final edge).
It is important to maintain consistency when shaping bevels. It is important to maintain a consistent approach to the cutting edge. The bevel should have only one facet. The angle between adjacent bevels must be perfectly divided at the cutting edge.
When grinding the final cutting bevel angle, I set the tool rest at a low angle relative to the grinding stone (about as low as I can get) . Veritas’ tool rest is slotted and articulated for the stone. This allows me to grind with good support. As I grind the bevel, I judge that the tool rest angle I have set gives me a bevel length that is about 2-1/2 times the iron thickness. That is a good cutting angle; its in the range of 25- 30. To optimize the cutting angle, I might need to adjust the angle of the tool-rest as the bevel develops.
The iron is resting flat on the tool rest, my forefinger acts as a fence against the proximal edge of the rest and my thumb is pressing on the iron face to advance or retreat the iron as I grind. To keep the developing bevel square with the stone, the iron is canted to one side or the other. The cutting action happens in the center, between the right and left thirds of the wheel, back and forth. The iron should not be allowed to slip off the wheel’s edge.
The middle bevel is usually ground first, followed by the left bevel. I save the fillet for last. Be very careful about cooling the iron as the edge becomes thinner. Take the edge down to a skinny 81 cm or so in order to preserve the temper. While you are grinding, make sure that the final bevel width is sufficient to allow for a good cutting angle. The edge should be very consistent in thickness at this point. Do not grind the edge.
The second bevel should have the same width as the first bevel. Tweak this bevel until the arris is sharp and hits the intersection of the two bevels. Grind the fillet edge to a steep bevel, but hold this well short of the final dimension.
The bevels at this point are all hollow ground and quite wide. With a good sense of touch and great care, its possible to have the iron rest flat on the bevel on the honing stone. Rather than push the iron straight down the stone, I hold the iron sideways so Im honing along the length rather than the width of the bevel. This gives me a straighter bevel and less inadvertent introduction of camber. You will taper the bevel along its length if you don’t distribute the pressure evenly. Stop every stroke or two on the stone and inspect the progress. It takes only a thin 1/81 cm to reach the burr stage.
I have two approaches to honing. For one-off irons, I generally use a medium diamond plate followed by Japanese stones (#800, #1,200 and #4,000 grit). I hone the face of the iron first, and then turn my attention to the bevels. I use the #4,000-grit stones to remove the burr when working on the bevels.
I also use the WorkSharp. I apply the same grit to both sides of the glass plate, and then work my way through several grits (in stages ranging from #36 to #2,000 depending on how much work I have to do). The throughput with this device is amazing (I often sharpen 30-40 chisels and 30 block, jack and smoothing planes over a four-hour period). To maintain the perfect bevels, I need a very fine sense of touch because I work on the machine’s upper surface. Cooling is necessary at all stages.
Throughout this honing process, I focus on the two long bevels, testing the progress by reinserting the iron in the plane body. I make sure that the plane body profile is parallel to the bevels and that the intersections of the bevels match the plane profile’s arris. Both bevels should be corrected if the intersection is not correct. Changing only one bevel will move the arris between the two bevels to one side or the other. This arris needs to be in line with the intersection of the two bevels.
Once I am completely happy with the two long bevels, I turn my attention to tweaking the fillet bevel. Maintaining this part of the iron fat until this point keeps me from being found slumped over my bench crying a bucket full of tears. Creep up to the final dimension, first with the rough grind, then with the honing steps. This bevel is very small so it is easy for you to create multiple facets by working down the bevel. Final honing is always done by hand so I dont overshoot the dimensions. The bevel ideally should have a rhombohedron shape and extend to below the plane body profile.
P.S. Heres the above in PDF format, should you wish to download it for use in the shop:PlaneIronSharpening
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