A Knife for Marking Dovetails
I have lost count of the different types of marking knife designs I have come up with in recent years.
The ones below are by far the most comfortable to use, and the best design for marking dovetails. They handle like a pencil, and feel really comfortable to hold. Although slim-line, these are quite tough, but keep in mind that they are designed for marking lines and not for carving.
The knife and scratch awl in the upper picture are Jarrah, while those in the lower picture are She-oak and Jarrah.
Length of the handle is 6"/150mm, the blades are 2mm thick tool steel, and the ferrule is brass. The double bevel is intended for left and right use.
Here is the sequence I
follow in making the marking knives and installing the knife blades.
This should give you a good idea of the work involved so as you may
build your own.
First of all, I have a Jet mini lathe, which is perfect for small work such as this.
The body is turned and complete, with the exception of a piece at the end, which is removed and shaped it by hand at the end.
The ferrule begin life as part of a shelf support bushing. The blades are created from jigsaw blades. I can get two knife blades from each jigsaw blade.
The teeth of the blades
are ground off on a belt sander, the faces are flattened and
smoothed, then polished on waterstones. Emphasis is given to keeping
the back area under the bevel flat. The bevels are ground on the belt
sander, then honed by hand.
To install the blade, a kerf is cut, first with a thin Japanese saw, then widened on my LN dovetail saw. The body is drilled for the tang. The pieces are pushed together (usually a tight fit) with a little epoxy.
A few more measurements: the ferrule and the tang are each 5/8" deep. This should be plenty support for the blade. The blade is 1 1/4" long (above the ferrule) and about 1/4" wide. The body of the knife is 6" long.
This was one of the first knives I made in this style. It went to a good friend. The wood is Sheoak.
There are other variations possible, such as this Harlequin Jarrah and She-oak combination ..
.. and one of my favourite users, a Jarrah and Olive combination …
An update on methodology ..
I now make the blade from HSS jigsaw blades and no longer from tool steel. These are indestructible and probably will not require resharpening for years, if ever. They are lapped and shaped, then ground by hand.
I have made about a hundred of these marking knives and awls over the past few years and in that time had only 2 fail. But this nagged at me, and so I decided to increase the strength by reinforcing the area around the ferrule by silver soldering on a thicker base (steel or brass, whatever is available). The brass ferrule is epoxied on for finish rather than having any structural reason.
Grinding Blades from a Jig
When I first began making marking knives I would grind each blade individually. This involves marking the V-angle, grinding at an approximate angle, and finishing by honing by hand.
Eventually I built a jig that not only makes the grinding easier, but blades with accurate and repeatable bevels.
The following jig creates a 55° V-angle, and is angled for a 30° bevel.
This is a length of angle iron to which is bolted a Jarrah template.
The blade is clamped using the cutout as a guide. The following is a mock-up (the jigsaw blade used here would normally be stripped of teeth and surface ground)...
Now let's backtrack a little. See the cut out in the Jarrah guide? The wooden section was sawn on a bandsaw and the waste was saved. This is attached to a disk sander and acts as a fence to grind the V. Do one side, flip, and grind the other. I use 80 grit disks ..
The jig may now be used on your grinder of choice. My preference is the Tormek, as I follow the hollow grind with freehand hone on a waterstone. Alternately, use a beltsander, where you have a wider range of grits than a grinder, but the flat grind is not as easy to freehand as a hollow on a wheel. Lastly, there is a dry grinder. I use a 8” 46 grit 3X wheel, which runs quite cool (however the temper of HSS steel is nearly impossible to affect with the heat from a grinder).
Belt sander (see “Beltsander Grinder” for details of this jig)
Updated August 2009