Marking and layout tools — we’ve dedicated entire articles to them, and that should speak to their importance in the shop. Being able to accurately mark parts and strike layout lines are tasks where a quality marking knife is without equal. The marking knife you see here can be made in a quick afternoon in the shop, and works in some great turning and metalworking.
A SPEARPOINT TIP.
As you can see in the photo well and drawing, the business end of this marking knife is a spearpoint blade. This design has a sharp tip, with bevels on both edges. This means it can be used to mark on both the left and right sides of parts, as well as used in both hands. The backside of the blade is honed flat with no bevels so that it can be referenced flat along a straightedge for accurate marking.
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| The shape of this blade is ideal for marking a variety of parts. The flat back of the blade offers a wide reference surface for scribing accurate lines. |
Moving up from the blade, you’ll see that there’s a brass ferrule tying the blade to a walnut handle. The ferrule (as well as the handle) are turned at the lathe. If you’ve never turned brass at the lathe, you’re in for a treat. With sharp tools and light cuts, brass cuts like butter.
The handle design shown here is one that our designer, Chris Fitch came up with. However, feel free to get as fancy as you’d like with the design (or wood) on yours. Now, let’s head into the shop get started.
It Will Cut — The Blade
The business end of the marking knife is the blade. At its core, a marking knife really only needs a blade. Many marking knives are simply bars of steel with a bevel ground on one end. Of course, we’ll fancy ours up in a bit. Let’s start with the blade.
WONDERFUL O1. Of all of the steels available, O1 tool steel is my favorite. It works very easily, it takes a wicked sharp edge, and it’s easy to sharpen. O1 tool steel is readily available from online retailers. See our sources on page 50.
With your blank in hand, you may be tempted to start by cutting it to length. Hang on though — you’ll find it easier to work on the blade with a bit of extra material to hold onto.
Before we start working on the blade, let’s make some layout lines to guide our work. Use a black permanent marker (or layout fluid if you have it) and scribe a few layout marks onto the blade. Use the measurements in Figure 1 to mark these accurately.
The first task is to create the small swoops on each side of the blade. This “necked down” area is a nice detail, and provides a touch more visibility as you’re working in tight areas. These swoops are easy to make with a round file, or if you have a sanding drum for your drill press, you could use that too. Use a coarse grit to remove material efficiently.
BEVELS NEXT. Now, clamp your blade in a metal vise and grab a good file. It’s time to form the bevels. Instead of trying to create the shape of the end and the bevels in one go, I do this in a two-step approach. First, file off the corners to shape of the tip. This will create the spear point end. Take your time to ensure a symmetrical shape.
Once you have the tip shaped, you can start to form the bevels. Here, we chose a 30° bevel. It’s stout enough to not be fragile, but still holds an edge nicely. File the edges down until they’re just sharp. You will do the final honing after the knife is finished.
HEAT TREAT.
Now is the time to cut your blade to length and heat treat it. Heat treating O1 is easy. Use a propane (or MAPP) torch to heat the blade until a magnet will no longer stick to it. Once you’ve reached that point, plunge the steel into vegetable oil to harden it (the O in O1 stands for oil).
Forged Steel
When heat treating a blade, the goal is to get the entire cutting edge to an even temperature. Hold the blade in a pair of vise grips, and move it back and forth through the flame for an even heat. You want the entire cutting tip to be non-magnetic before quenching.
After it’s cooled, check the edge with a file — a file will not bite into a properly hardened edge. If you’re successful, you can pop it into an oven at 400° for a couple of hours to temper it. This reduces the brittleness of the hardened steel. Clean up any scale off the steel with sandpaper, and turn your attention to the handle.
HANDLE & FERRULE
Looking at Figure 2, you’ll see that the handle starts as one blank that’s been ripped in half. This allows you to create a mortise for the blade before turning it.
MORTISE FIRST. After selecting your stock and ripping it in half, load up a straight bit in the router table. You’ll want to rout a shallow stopped groove in each part, as you see in Figure 2. Test the fit by clamping the blank back together and inserting the blade. Adjust the fit as needed for a slip fit, and glue the handle back together.
TO THE LATHE. Now, it’s time to head to the lathe and turn the handle. Hold the handle in a chuck, with the mortised end supported by the tailstock. Use a spindle roughing gouge to turn the entire blank round. The brass ferrule will slip over a tenon. Form this tenon with a parting tool (Step 1, below). As you form the tenon, remove the tailstock to test the fit. Once the ferrule slips over the tenon, epoxy it in place, and wait for it to cure.
Here’s where you can really start to experiment with shapes. Turn the handle to whatever shape you like. A slim shape is generally more comfortable to hold, and something tapered works well. As you turn the brass ferrule, take light cuts.
As long as your tools are sharp, the brass will turn nicely. Be careful trying to make a continuous cut between the wood and brass however—you’ll find the two materials will cut differently and have a tendency to leave a ridge.
Instead, get the ferrule and handle both close to the finished shape, then blend them together with sandpaper. Finally, part the handle off of any excess held in the chuck.
Epoxying the blade into the handle is the final step before sharpening. A five-minute epoxy works well. Make sure to wipe any squeeze out away with acetone before the epoxy cures and hone the blade to a razor-edge.
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| Turn a tenon on the tailstock end of the workpiece. Use a pair of calipers to measure the inside diameter of the brass tube, and transfer that to the blank. | Pull the tailstock away and test the fit of the tube. It should be snug the entire length of the tenon. Once you’re happy with the fit, cut the tube to length. |
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| Spread epoxy on the tenon and press the ferrule into place. Wipe away any squeeze-out. Hydraulic pressure may push the ferrule off the end, so bring the tailstock up to “clamp” it in place. | Start by turning away the brass ferrule, and getting that to shape. Leaving a large bulk of material in the handle will help reduce chatter from cutting the harder brass. |
