BeaverCraft 4.3" Draw Knife Sheath | Ergo-Grip & Heavy Duty

Standard 3D printed sheaths can be slippery and difficult to remove safely. This design features a completely new "Ergo-Pull" Handle—a concave, scalloped fin running the length of the spine. This gives you a secure, comfortable grip to easily overcome the snap-fit tension when removing the cover.

This model was developed through an iterative design process with AI assistance to perfect the snap tolerances, structural integrity, and ergonomic handling.

Key Features

• Ergo-Pull Handle: A seamlessly blended, scalloped grip fin allows you to pinch and pull the sheath off safely without your fingers slipping.

• Floating Edge Protection: A dedicated internal channel ensures your freshly honed edge hangs in a void, never touching the plastic.

• Single-Bevel Fit: The internal geometry is contoured specifically for the BeaverCraft's flat-back/single-bevel profile.

• Vertical Grain Strength: Designed to be printed vertically. This gives the clip "hoop strength," allowing the arms to flex and snap securely over the blade without cracking along the layer lines.

• Seamless "Monolithic" Design: The grip fin blends perfectly into the main body with matched curvature, eliminating stress risers and gaps.

Print Instructions (Critical!)

This part relies on specific slicer settings for its strength.

• Orientation: VERTICAL (Standing up). Do not print this flat on its back. Printing vertically ensures the plastic loops around the blade like a strong flexible band.

• Brim: REQUIRED. Because this is a tall print (119mm) with a relatively narrow footprint, use a 5mm - 10mm Brim to anchor it to the bed.

• Material: PETG is highly recommended for durability and flex, but PLA+ works well due to the heavy 3.2mm wall thickness.

• Perimeters: Set to 4 or more. You want the walls to be mostly solid plastic loops, not infill.

• Supports: None needed. The fin is designed with angles that print cleanly without support.

Usage

1. Look for the small notch on the outside corner of the sheath (near the opening - I also overlaid a green line that the bevel sits against).

2. Align the flat back of your draw knife with this notched side.

3. Press the sheath over the blade until it snaps into place.

4. To remove, simply pinch the Ergo-Pull handle and pull.

Source Code (OpenSCAD)

This design is fully parametric. You can adjust the variables at the top of the script to fit any drawknife.

How to use:

1. Download and install OpenSCAD (it's free).

2. Copy and paste the script below into the editor.

3. Change the values in the "Dimensions" section to match your tool.

4. Press F6 to render and F7 to export as STL.

OpenSCAD

// ==========================================
//   PARAMETRIC DRAWKNIFE SHEATH GENERATOR
// ==========================================

// --- 1. BLADE DIMENSIONS (Measure your tool) ---
// Total length of the sheath. 
// TIP: Measure distance between handles and subtract 1-2mm for clearance.
length = 119;       

// Maximum thickness of the blade spine (Z-height).
blade_thick = 3.0;  

// Depth of blade from sharp edge to back spine (Y-depth).
blade_depth = 19.5; 

// Height of the bevel.
// For single-bevel knives, this is how far up the angled face goes.
bevel_width = 5.0;  

// --- 2. RETENTION SETTINGS (Adjust for fit) ---
// How much the locking nubs stick out into the blade path.
// Higher = Tighter grip. Lower = Easier to remove.
// Recommended: 0.25 (Tight) to 0.15 (Loose).
nub_protrusion = 0.25;

// Radius of the locking nubs. 
// Larger radius = Smoother entry/exit.
nub_radius = 1.2;

// --- 3. ERGONOMICS & STRENGTH (Advanced) ---
// Thickness of the walls. 
// 3.2mm allows for ~8 perimeters (very strong).
wall_thick = 3.2;        

// Thickness of the bottom spine.
floor_thick = 5.0;       

// Depth of the pull-handle fin.
grip_depth = 12.0;       

// ==========================================
//      INTERNAL LOGIC (Do not edit below)
// ==========================================

// CALCULATIONS
body_real_width = blade_thick + (2 * wall_thick);
center_x = blade_thick / 2;
sheath_depth = 18.0; // Fixed depth relative to blade

linear_extrude(height = length) {
    union() {
        // 1. THE BLENDED GRIP FIN
        translate([center_x, -floor_thick])
        difference() {
            hull() {
                // BASE: Rounded to match body
                translate([0, 0])
                minkowski() {
                    square([body_real_width - 2, 0.01], center=true);
                    circle(r=1, $fn=20);
                }
                // TIP: Rounded handle tip
                translate([0, -grip_depth])
                circle(d=4.0, $fn=30);
            }
            // Finger Scoops
            scoop_radius = 6.5; 
            scoop_x_offset = body_real_width/2 + scoop_radius - 2.5;
            scoop_y_pos = -grip_depth * 0.55;
            translate([-scoop_x_offset, scoop_y_pos]) circle(r=scoop_radius, $fn=40);
            translate([scoop_x_offset, scoop_y_pos]) circle(r=scoop_radius, $fn=40);
        }

        difference() {
            // 2. MAIN BODY (Symmetric)
            translate([-wall_thick + 1, -floor_thick + 1])
            minkowski() {
                square([blade_thick + (wall_thick * 2) - 2, sheath_depth + floor_thick - 2]);
                circle(r=1, $fn=20);
            }

            // 3. THE CUTOUT (Single Bevel Profile)
            polygon(points=[
                [-1.5, -2.5],
                [blade_thick * 0.5, -2.5],
                [blade_thick, bevel_width],
                [blade_thick, sheath_depth + 10],
                [0, sheath_depth + 10],
                [0, 0]
            ]);
        }

        // 4. ROUNDED SNAP NUBS
        translate([-nub_radius + nub_protrusion, sheath_depth - 1.5])
        circle(r=nub_radius, $fn=30);
        translate([blade_thick + nub_radius - nub_protrusion, sheath_depth - 1.5])
        circle(r=nub_radius, $fn=30);
    }

    // 5. MARKER (Indicates Flat Side)
    translate([-wall_thick, -floor_thick/2])
    circle(r=0.6, $fn=10);
}

Customization Guide

• Too Tight? Decrease nub_protrusion from 0.25 to 0.20.

• Too Loose? Increase nub_protrusion to 0.30.

• Different Length? Simply change length = 119 to your measured distance.

• Double Bevel Knife? This design is specific to single-bevel (flat back) knives. For double bevels, you would need to modify the polygon points in section 3 to be symmetric.