Marking Knife with Replaceable Blades

I read a joke the other day, "Growing your own tomatoes is the best way to devote 3 months of your life to saving $2.17". I feel the same way about these marking knives. It would cost me about $250 ($300 with exotic timber) to import one from either the UK or the USA. Instead, I spent nearly 3 days making my own ... Okay, I made several, but some will likely be given away. I may sell a couple to recoup my costs. But nearly three days ....

I said I would show how these are made. Specifically, it is the blade carrier that all are interested in. I watched video by Matt Estlea on YouTube, where he spent months struggling to come up with the design. My design is different - blade carrier and knife shape - and it did not take more than an hour to come up with the concept. It is a little different to others making this style of knife. But it is simple and strong.

This is the design being used by a few makers on the Internet, and similar to Matt’s version:

The construction ends up being straight forward, but the blade carrier requires a metal lathe, which I do not have.

The cost of the build is not in the materials; the cost is in the tools and the time it will take to machine each part especially, as in my situation, I do not possess metal working tools.

Start out with a solid brass rod with an external diameter of 9mm. 9mm is the width of the Swann-Morton blade shafts. The knives are built around these blades. Add to the a brass tube with an external diameter of 10mm and walls of 0.5mm ...

These will fit together perfectly ...

You need a slitting blade (the type used to create the brass back for backsaws). This one cuts a 0.65mm kerf. I had measured the Swann-Morton blade I use, and it was 0.6mm. In retrospect, I should have used a cutter with a 8.0mm kerf. Mine turned out a smidgeon tighter than I would have liked – it appeared to close up slightly once inside the tube. I later opened the kerf up a little with a diamond file.

The 9mm internal diameter is a must for a tight fit - you do not want a looser fit as downforce will cause the blade to move back-and-forth with downforce.

Slitting blade creating the slot for the blade …

Note that the brass rod is held in a holder - essentially a V-groove. Photo shortly - and on the left side of the cutter against the fence. This is to ensure that the cutter turns into the rod.

Below you see the v-groove holder and clamp. It holds here the rod inside the tube, both cut to 40mm in length. The purpose is to drill a hole, which will be tapped for the 3mm set screw ...

This is what you want ...

Later, any rough edges with be polished away on a wheel.

At this point it is time to make the handle.

Cut the blanks, and drill the mortise for the blade carrier now (this cannot be done later). I thought that 10mm would be a good fit, but ended up around 10.5mm leave some space later for epoxy.

This is the result of preliminary rough turning to 17mm diameter ...

Handles were then turned to shape and sanded ...

It is easier to maintain consistency when turning en masse.

The handles were sanded to 400 grit and finished with Shella Wax. Below is an assembled Mk1 ...

Total length is 150mm (6"), excluding the blade. The body is around 16mm at its widest point.

The Mk 2 design was intended to match the original dovetail marking knife I designed, and later was made by Chris Vesper. Some of you have this one.

A last point about blades.

There are two Swann-Morton blades I use: the SM01 (with the horizontal edge), and the SM03 (with the angled edge) ...

Each has a different effect on cutting. With the SMO1 I have tended to hold the Stanley knife in a fisted grip. That is, palm over the handle, holding it lower. This facilitates a heavy stroke ...

SMO3 enables the handle to be lifted and angled up, and the preferred grip for this is like holding a pencil (better for lighter marking, such as dovetails - which is why the double bevelled dovetail knife excels in this regard) ...

Of course, the handle with the horizontal edge blade may also be held like a pencil, but the angled edge is more comfortable for this.

Regards from Perth

Derek

April 2025