Brackets and mounts
Picatinny Accessory Rail
- Bounding box
- 21.2 × 290.0 × 12.0 mm
- Engine
- Precision B-rep
- Parameters
- 17
- Published
- September 15, 2026
Download
Free to download and use. See the terms.
The prompt
Create a single-piece 14-slot Picatinny accessory rail. Units are millimetres. IMPORTANT: Construct the rail from an explicitly dimensioned symmetric 2D cross-section first, then extrude that cross-section longitudinally. Do not invent or reinterpret the cross-sectional geometry. COORDINATE SYSTEM: For the transverse cross-section: X = horizontal distance from the rail centreline. Z = vertical height. The rail is symmetric around X = 0. Create the mounting base first. BASE CROSS-SECTION: - Width: 21.0 mm - Thickness: 3.0 mm - Bottom surface: Z = 0 - Top surface: Z = 3.0 - Left edge: X = -10.5 - Right edge: X = +10.5 Create the Picatinny rail profile directly above this base. UPPER PICATINNY PROFILE: Create a flat top surface: - Left top corner: X = -10.6, Z = 12.0 - Right top corner: X = +10.6, Z = 12.0 From each top outer corner, create a straight 45-degree engagement face descending inward. Left side: - Start: X = -10.6, Z = 12.0 - End: X = -8.0, Z = 9.4 Right side: - Start: X = +10.6, Z = 12.0 - End: X = +8.0, Z = 9.4 Continue vertically downward from: - X = -8.0, Z = 9.4 - X = +8.0, Z = 9.4 Connect these sides into the mounting base at Z = 3.0. The resulting rail must be one continuous solid. CRITICAL CROSS-SECTION REQUIREMENTS: - Flat top. - Symmetrical left and right sides. - 21.2 mm maximum top width. - Two 45-degree angled clamping surfaces. - No undercut underneath the upper rail. - No horizontal lower flange. - No I-beam profile. - No mushroom profile. - No T-slot profile. - No narrow central neck. - The upper rail must transition directly into the supporting body and base. EXTRUSION: Extrude this cross-section to a total length of 145 mm. PICATINNY RECOIL SLOTS: Cut 14 identical transverse slots through the upper portion of the rail. Each slot: - Width along longitudinal axis: 5.23 mm - Slot pitch: 10.01 mm - Slots perpendicular to longitudinal axis - Slots centred and evenly spaced - Cut downward from the top - Do not cut through the 3 mm mounting base MOUNTING HOLES: Create three vertical through-holes through the centreline of the rail and base. Hole diameter: 4.5 mm. Longitudinal positions measured from the centre of the component: - Hole 1: -60 mm - Hole 2: 0 mm - Hole 3: +60 mm Add a concentric counterbore to each hole: - Diameter: 8.0 mm - Depth: 2.5 mm - Counterbore enters from the TOP surface. Do not create any additional arcs, grooves or recesses around the mounting holes. FINISH: Add 0.5 mm chamfers to the front and rear ends only. Do not chamfer or fillet the Picatinny clamping surfaces or recoil-slot edges. OUTPUT: One single solid component only. Do not model screws. Do not model T-nuts. Do not model an M-LOK handguard. Do not model a mating Picatinny component.
Parameters
| Name | Value | Range |
|---|---|---|
| Base Width | 21 mm | 15 – 30 |
| Base Thickness | 3 mm | 1 – 8 |
| Top Width | 21.2 mm | 15 – 30 |
| Top Height | 12 mm | 8 – 20 |
| Clamp Lower X (half width) | 8 mm | 5 – 12 |
| Clamp Lower Z | 9.4 mm | 5 – 15 |
| Extrusion Length | 145 mm | 50 – 300 |
| Slot Count | 14 count | 1 – 30 |
| Slot Width | 5.23 mm | 3 – 10 |
| Slot Pitch | 10.01 mm | 5 – 20 |
| Hole Diameter | 4.5 mm | 2 – 8 |
| Counterbore Diameter | 8 mm | 5 – 12 |
| Counterbore Depth | 2.5 mm | 1 – 5 |
| Hole 1 Position | -60 mm | -100 – -20 |
| Hole 2 Position | 0 mm | -20 – 20 |
| Hole 3 Position | 60 mm | 20 – 100 |
| End Chamfer Size | 0.5 mm | 0.1 – 1.5 |
Every value above is a live dimension. Open a model like this in the editor and each one becomes a slider you can drag before exporting.
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