CNC Machining for Knife Making: A Complete Guide for Beginners

CNC machining has opened up the art of custom knife making to anyone with access to a CNC mill or router. Instead of spending hours cutting, grinding, and sanding a knife profile by hand on a belt grinder, you can design the knife in CAD software, generate toolpaths in CAM, and let the machine cut the profile accurately in minutes.

I originally started making custom knives by hand using only a basic hacksaw and files. The first few knives took several days each and never matched the original design exactly. When I switched to using CNC for profile cutting and bevel grinding, the overall quality of my knives improved dramatically and the time dropped from days to just a few hours.

This comprehensive guide covers the complete CNC knife making process from material selection and design through profile cutting, bevel machining, scale cutting, heat treatment, and final assembly and finishing.

Materials for CNC Knife Making

Blade Steel Options

1095 high-carbon steel is the most common knife blade material for CNC machining. It is easy to machine in the annealed state, heat treats reliably, and takes a very sharp durable edge. The steel machines similarly to mild steel with slightly higher cutting forces due to the higher carbon content. 1095 is the most forgiving material for beginners to start with because it is widely available, affordable, and responds well to basic heat treatment equipment.

O1 tool steel is another excellent choice for CNC knife making. O1 machines well in the annealed state, heat treats with minimal distortion compared to other tool steels, and produces an excellent edge that holds well. The steel is more expensive than 1095 but the heat treatment process is more forgiving because the oil quench is less severe than water quenching.

O1 tool steel is another excellent choice. O1 machines well in the annealed state, heat treats with minimal distortion, and produces an excellent edge. The steel is more expensive than 1095 but the heat treatment process is more forgiving for beginners.

Stainless steels like 440C and S30V are more difficult to machine due to their hardness and work-hardening tendency. These require sharp carbide tooling at low RPM with consistent feed rates. Titanium is commonly used for knife handles. Grade 5 titanium machines well with carbide tooling at low RPM and moderate feed rates with flood coolant.

Blade Thickness

Fixed blade knives typically use 0.100 to 0.125 inch thick material. Folding knives use thinner material at 0.060 to 0.080 inches. Thicker material requires more machining passes but produces a stronger blade.

Designing the Knife in CAD

Profile and Bevel Design

The knife design starts with a 2D profile drawing in CAD software. The profile includes the blade shape, the cutting edge geometry, the spine contour, the ricasso where the blade meets the handle, the tang shape, and the handle contour. The complete profile is a single closed shape representing the exact outline of the finished knife blade. All geometry must be drawn as clean closed contours for CAM toolpath generation to work correctly without errors.

The bevel is the angled grind on each side of the blade that forms the cutting edge. The bevel is typically ground at 15 to 20 degrees per side for a total included angle of 30 to 40 degrees at the cutting edge. A lower angle produces a sharper edge that is less durable. A higher angle produces a more durable edge that does not cut as aggressively. The bevel can be programmed in the CAM software as a 3D surface toolpath or machined as a 2D profile with the part tilted on an angled fixture.

Design Considerations for Machining

When designing the knife for CNC, avoid sharp internal corners in the tang and handle areas. End mills create a radius in every internal corner equal to the tool radius. If your design has a sharp corner at the junction of the blade and tang, it will need hand filing to clean up. Design generous fillets (R0.062 or larger) at all internal transitions.

Place the knife profile in the CAD file with the spine aligned parallel to the X-axis and the blade tip pointing in the positive X direction. This orientation provides the most rigid cutting direction for the end mill during profile cutting. The tang should be positioned so that the attachment holes align with the machine axes for straight-line drilling.

Tang and Handle Design

The tang is the rear section of the blade that extends into the handle. A full-length tang extends the full length and width of the handle for maximum strength. A partial or hidden tang extends only part way. The tang includes precisely located holes for handle scale attachment pins.

The handle scales are the two pieces of material that form the handle on each side of the tang. Common materials include hardwoods, G10, Micarta, carbon fiber, and stabilized wood. The scales are CNC profiled to match the tang outline with precisely located holes.

Cutting the Knife Profile

Tooling and Strategy

The knife profile is cut from flat steel stock using a 2D contour toolpath. Use a 1/8 inch or 3/16 inch carbide end mill for profile cutting. A smaller tool allows tighter inside corner radii. A larger tool removes material faster on straight sections. Single-flute carbide tools provide excellent chip clearance for steel.

Cut the blade profile in three or four passes at increasing depth increments: first pass at 0.020 inches, second at 0.050 inches, third through most of the remaining material leaving 0.005 inches, and the final pass to release the part.

Profile Cutting Parameters

Material	Tool	RPM	Feed	Passes	Coolant
1095 steel	1/8“ carbide	6,000	10 IPM	4	Mist or air
O1 steel	1/8“ carbide	6,000	10 IPM	4	Mist or air
440C stainless	3/16“ carbide	4,000	6 IPM	4	Flood or mist
Titanium	1/8“ carbide	3,000	8 IPM	5	Flood coolant

Machining the Bevel

3D Surface Method

The bevel can be machined with a 3D surface toolpath in CAM. The toolpath follows a ruled surface from the spine down to the edge at the specified angle. A ball nose end mill produces the smoothest surface finish — 1/4 inch or 3/16 inch diameter is typical.

The bevel is machined in multiple passes with decreasing stepover: roughing at 0.020 inch, semi-finish at 0.010 inch, and finishing at 0.005 inch. The finishing pass direction should follow the cutting edge direction for a consistent surface.

Tilted Fixture Method

An alternative is to tilt the blade on a custom fixture and cut the bevel as a simple 2D contour. The part is mounted on an angled fixture that presents the bevel surface perpendicular to the tool axis. This method is significantly faster than 3D surface machining but requires a custom fixture for each bevel angle.

Bevel Parameters by Material

Material	Tool	RPM	Feed	Stepover	Passes
1095 steel	1/4“ ball nose	6,000	12 IPM	0.010“	3
O1 steel	1/4“ ball nose	6,000	12 IPM	0.010“	3
440C stainless	3/16“ ball nose	4,000	8 IPM	0.008“	4
Titanium	1/4“ ball nose	3,000	10 IPM	0.008“	4

Cutting Handle Scales

Setup and Drilling

The handle scales are profiled from handle material using the same 2D contour toolpath approach as the blade. The scale material is held in a vise with soft aluminum or plastic jaws that prevent marking the visible surface.

Scales are typically 0.100 to 0.150 inches thick depending on the handle material and knife design. Thicker scales provide a more substantial grip but add weight. The scale profile matches the tang profile with approximately 0.020 inches of additional material left for sanding and shaping after assembly.

Drill the scale attachment holes in the same CNC setup as the profile cutting operation. The hole positions in the scales must match the tang holes exactly for proper alignment during assembly. Use a center drill to start the holes at the correct locations and a standard twist drill to finish to the final diameter.

Material-Specific Tips

Hardwoods like walnut, maple, and ebony machine well with standard carbide tooling at moderate speeds. Use 2-flute upcut bits to prevent tear-out on the visible surface. G10 and Micarta are abrasive composite materials that wear tools faster — use carbide tooling and expect reduced tool life. These materials produce fine dust that requires a dust mask and proper ventilation during cutting.

Carbon fiber is highly abrasive and conductive. Use diamond-coated or carbide tooling at moderate feed rates. The dust is irritating to skin and lungs — always use a respirator and vacuum collection when machining carbon fiber handle materials.

Finishing and Assembly

Heat Treatment

After CNC machining is complete, the blade requires heat treatment to harden the steel for use. The process involves heating the blade to the critical temperature for the specific steel type (typically 1,450-1,500°F for 1095), quenching it in oil to harden it, and then tempering at the specified temperature (typically 350-400°F for 1095) to reduce brittleness. Heat treatment changes the blade surface color and may cause slight warping that requires careful straightening while the steel is still warm.

The blade surface after heat treatment is cleaned of scale and finished to the desired appearance. The CNC-machined bevel needs only light sanding with fine 400 to 600 grit sandpaper to remove any visible tool marks from the ball nose end mill. The blade can be etched with the maker’s mark using chemical etching or laser engraving after final sanding.

Final Sanding and Assembly

The handle scales are sanded to final shape after assembly to the tang. The scale material is profiled slightly oversize in the CNC and sanded to the final shape after gluing. The sanding process blends the scale contour smoothly with the tang profile for a seamless transition.

The completed knife is assembled with corrosion-resistant brass or stainless steel pins through the tang and scale alignment holes. The assembly is clamped firmly in a knife vise until the epoxy or cyanoacrylate adhesive cures completely — typically 24 hours for full strength. After assembly, the knife is sharpened to the final edge geometry using a guided sharpening system or water stones.

Testing and Final Inspection

Check that the blade is centered in the handle, the edge is uniform, and the handle surface is smooth. A well-made CNC machined knife should perform every bit as well as any handmade knife because the blade materials and heat treatment processes are exactly the same regardless of how the profile was cut. The CNC machining process simply produces a more accurate and repeatable starting point for the finished knife than hand filing and grinding can achieve consistently by manual methods alone.

Here is a sample G-code header for a knife profile program:

; Knife profile — 1095 steel, 1/8" carbide end mill
G90 G94 G17 G54
G21
M03 S6000
M08                ; Mist coolant on
G00 X0 Y0 Z5
G01 Z-0.02 F10    ; First pass
; (profile contour follows)

The combination of CNC precision and skilled hand craftsmanship produces knives that are both functional and beautiful. Every knife maker who tries the CNC approach discovers that the machine handles the tedious and repetitive material removal tasks while leaving the creative and skilled parts — heat treatment, handle shaping, and final sharpening — to the maker.

For more information on materials and tooling, see our CNC End Mill Selection Guide and Feeds and Speeds Guide. For surface finishing, see our CNC Surface Finish Guide.