carving knife handle

Printable handle for a carving knife. Very convenient tool for post-processing 3D prints, which is not all that different from carving wood. Good addition to a deburring tool.

Blade

My blades were made from blanks about 100mm x 10mm. I recommend getting material 3mm or slightly thicker, which can give nice wide bevels, easy to register on a carved piece. Thinner blades also work, they just aren't as easy to control.

The blade needs to be hardened and tempered, but if you don't feel up to heat-treat the steel, you can go for material that's treated already: circular saw blades, hedge shears, lawnmower blades, and so on. They are intended for cutting, even if don't have the best temper for a carving knife in particular. Be careful not to overheat this material when cutting the blank, it can ruin the temper (if you can hold it in hand, even if it's hot, you're still good).

A rectangular blank can be cut out with a rotary tool (Dremel-like) and shaped with a file, you don't need fancy tooling.

Blade geometry

A carving knife's blade typically has a single bevel on each side. This way you have a flat face to put on the carved piece and just a slight lift starts the cut. This means that wider bevels are easier to control, thus a thicker blade is usually better. My day-to-day carving knives have 3mm blades; 1.4mm blades I made from circular saw blade are slightly more difficult to use due to narrow bevels.

Next is the bevel angle. The more acute angle, the longer bevel you can get and the easier the blade cuts, but the edge gets fragile, easy to bend or chip if you twist the knife during a cut. For reference, my regular knives have angles 20°-22.5°, making a sharp but delicate edge. 30° or 35° are probably better choice for your first carving knife, mostly for edge durability against abuse.

NOTE: I was grinding the bevels to "this angle looks about right". You don't need any fancy jig or installation to get a good shape.

If you only have thin blade material, you can still get a relatively wide bevel if you grind it on one side only, similar to a grind of a woodworking chisel. I recommend to put the bevel on the side of your dominant hand when you cut by pulling the knife.

Print preparations

Cut the handle in three pieces: left and right scales and a spacer, which should be as thick as your blade. You can use the pre-cut STL and adjust the spacer thickness, or you can take a full handle and cut it yourself.

The spacer needs a cutout for the blade; you can easily add a negative volume in your slicer. One of the attached photos shows how it looks after the print. The handle includes a rectangular pocket for an alignment pin. The pocket's dimensions are 25x10x4mm, so you may want to print a 25x8x4mm cuboid, too.

Assembly

My knives were glued with epoxy. I expect contact cement to also work well, since it bonds plastic and metal. I wouldn't trust CA glue, as it becomes brittle with time, but if it fails, you can clean it off from the blade with acetone, and the rest of the knife doesn't need much work to recreate, so it may be worth a try.

Using the knife

The grips I use the most often are:

• cutting towards my thumb; all the strength comes from the thumb pressing the element against the knife

• cutting away from my body; the strength comes from the hand holding the element, that is, my left thumb is pressing the back of the knife

  • a variant of this: my left thumb stays fixed and is used as a pivot for the knife; I can reach into inside corners with the tip of the blade