Hawk-Lock Kinetic Folder [assisted-opening system] - Free 3D Print Model

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Trent Studio

Tools>Gadgets

IP Report

Print Profile(3)

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A1 mini

H2S

H2C

P1P

P2S

H2D

P1S

X1 Carbon

H2D Pro

X1E

X2D

A2L

Basic version

Designer

2.1 h

1 plate

4.9(50)

Designer’s Reinforced Edition

Designer

2.1 h

1 plate

4.7(17)

BOX

Designer

3.1 h

2 plates

5.0(2)

Open in Bambu Studio

Boost

1176

3288

1.4 k

815

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Bill of Materials

Maker's Supply Kits and Parts

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M3 Socket Head Cap Machine Screws (SHCS)

M3x18 SHCS Machine Screw (10PCS) - AA161

M3 Socket Head Cap Machine Screws (SHCS)

Carbon Steel Hex Nut

2x10 mm Stainless Steel Dowel Pins (20PCS) - DA037

D2 Stainless Steel Dowel Pins

2x16 mm Stainless Steel Dowel Pins (20PCS) - DA010

D2 Stainless Steel Dowel Pins

Description

This design features a folding utility knife with a complex internal architecture, integrating a Hawk-lock mechanism and an assisted-opening system.

Mechanical Logic: The system is centered on a power-reserve spring. Upon engaging the flipper tab, the spring begins to compress and store potential energy. Once the blade reaches a rotation angle of approximately 60 degrees, the stored tension is released, driving the blade to a fully deployed and locked position.

Durability & Material Science: A key engineering consideration was the material creep common in 3D-printed polymers. To mitigate this, the internal springs are designed to remain in a low-stress state when the knife is either fully closed or fully locked. Significant deformation occurs only during the brief opening transition, ensuring long-term reliability of the printed parts.

Layout: The internal systems are partitioned within the handle scales: the left side houses the Hawk-lock mechanism, while the right side contains the assisted-opening assembly. This is my most refined mechanical design of the past few months.

Technical Specifications

Printability: Straightforward geometry; no supports required.
Hardware: * 2 x M3-18mm screws
- 2 x M3 nuts
- 1 x M3-6mm screw & nut (for blade retention)
Blade Compatibility: Standard Stanley Utility Blades (Model: 11-921H-22). These are globally available and easily replaceable.

Material Recommendation: This model was developed and tested using PETG. I cannot guarantee optimal spring tension with other materials (e.g., PLA or ABS). If you choose to print the body in a different material, I strongly recommend printing the spring components in PETG to maintain the intended mechanical properties.

Project Updates

1. Added Configuration: Designer’s Reinforced Edition

This version incorporates two metal pins into the base design to significantly enhance locking strength and the structural integrity of the stop pin.

Requirements: 2 x 2mm diameter metal pins.
Required Lengths: 10mm and 16mm.

The modeled diameter for the pin holes is 2.3mm. Under ideal conditions, this provides ample clearance for standard 2mm+/- 0.01mm pins.

However, some users have reported a very tight fit, making pin insertion difficult. I suspect these assembly challenges are likely caused by over-extrusion or the "elephant’s foot" effect on the initial layers, which can slightly constrict the hole's opening.

Recommendation: If you encounter significant resistance, you may need to use a 2mm drill bit to manually clear the holes for a smoother fit. This step may not be necessary if your printer’s tolerances are well-calibrated.

2. Added Configuration: Protective Storage Case

A dedicated storage case is now available. The lid features an integrated elastic tension clip for secure closure. Two nameplate options are included:

Branded Version: Features my personal logo.
Blank Version: Provided for customization. If you intend to give this as a gift, you can use your slicing software’s text tool to design a custom nameplate.

Assembly Instructions

It is highly recommended to watch the assembly video before proceeding.

1.Parts Overview: Lay out all printed components and hardware.

2.Locking Mechanism: Insert the locking spring into the designated recess of the left handle scale (Blue).

3.Left Sub-assembly: Snap the handle liner (White) over the locking spring to complete the left side.

4.Pin Installation: Insert the D-shaped locking pin (Orange) into the blade holder. No glue is required; the pin will be secured by the outer housing.

5.Core Assembly: Mount the blade holder (Black) onto the pivot of the left handle. Secure the backspacer (Black) into its corresponding slot.

6.Assisted System: Place the right handle liner (Blue) over the assembly and install the asymmetric assisted-opening spring (Orange).

7.Right Housing: Snap the right outer handle shell (White) into position.

8. Final Fastening: Secure the entire handle assembly using the two M3-18mm screws and nuts. Install the blade using an M3-6mm screw and nut to finalize the build.

The strength of 3D-printed knives cannot be guaranteed and they are suitable only for light-duty tasks, such as cutting paper or opening Amazon packages. Unless otherwise specified, all of my knife designs are intended for light-duty use only.

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Comment & Rating (88)

@Chriscut

Boosted

I print at least one of almost every folding knife you design. Thanks for continuing to design new knives. I check often to see what you've come up with next. This one is quite clever and works great, probably one of my favorites.

@nirav_a1

Print Profile

Designer’s Reinforced Edition

very good design but wasted one internal plate and blade holder where the metal pins go, the pin holes are not exactly the right diameter. I tried taping them but ended up throwing it away. pins are exactly 1.99mm. you should check the tolerances.

The profile uploader has replied

@lancezhc

Thank you for the detailed feedback. I appreciate you measuring the pins so precisely 1.99mm. To explain the design logic: the pin holes are set at 2.3mm$ in the model. In the context of 3D printing, a well-calibrated machine typically has a material overflow of approximately 0.1mm$ on the radius 0.2mm on the diameter). This means the effective diameter usually results in roughly 2.1mm. If you are using1.99mm or 2.0mm pins, they will indeed feel loose during pre-assembly.However, there are two engineering reasons for this choice:

@lancezhc

Replying to @lancezhc :

Mechanical Function: These pins are captured within the assembly; once the handle scales are secured, they cannot fall out. Their primary role is load distribution. The system is designed so that the 3D-printed structure deforms slightly under stress until it engages the metal pins. Even with a slight clearance, the pins will effectively share the stress once the mechanism is under load. Compatibility Trade-off: I considered an interference fit (e.g., a 2.1mm or 2.0mm hole), which would offer superior stress-sharing. However, considering the wide variance in printer accuracy and non-standard pin diameters globally, I opted for a looser tolerance. A slightly loose but functional fit is a better compromise than a design that is impossible to assemble for users with over-extruding printers. I apologize for the frustration during the build, but I assure you that once the knife is fully bolted together, the pins will perform their intended structural duty despite the initial play.

@nirav_a1

Replying to @lancezhc :

I completely agree with your statement and assessment, you are engineer and will not argue with you, tight tolerance are needed but the pins wil not fit in the hole, I literally hammered it in and ended up destroying it, lol. I checked the pins three times and they measured 1.98–1.99mm. Anyway thank you

@J3er1968

Boosted

Print Profile

Basic version

Danke 🙏

@user_683206619

This time the result is much better. There's no play. That's a very good result. I had to apply a little pressure with pliers to get everything to fit properly, but that's actually good.

@kibs.ink

Print Profile

Designer’s Reinforced Edition

Printed without issues. Tolerances were great, but I had to clean up the holes for the pins a bit with a drill. I’m impressed by the design and the print time. I’m also really happy with the monocolor look with this burnt titanium filament. a tip for anyone having a hard time finding the pins. I found several steel and brass nails that fit perfectly and just cut them to size.

@user_485119062

Great design! printed in PETG-CF

@user_1675708323

Print Profile

Basic version

It's a great model. I like the mechanism, It feels smooth and solid. Thanks for this great model.

@user_3147838872

Print Profile

Basic version

My first time with PTEG. Fantastic design.

(Edited)

@ThreeDT

Print Profile

Basic version

Printed great and works well.

@user_2459300217

I already have it printed, just missing the screws. It's true that a clip could be added to carry it on a belt. Otherwise, it's a fantastic design, and for the next one, I'll make it with colors and a name. I hope the clip is available soon!!! Thanks for the design

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This user content is licensed under a Standard Digital File License.

You shall not share, sub-license, sell, rent, host, transfer, or distribute in any way the digital or 3D printed versions of this object, nor any other derivative work of this object in its digital or physical format (including - but not limited to - remixes of this object, and hosting on other digital platforms). The objects may not be used without permission in any way whatsoever in which you charge money, or collect fees.

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