Custom UGA clamps
The metal clamp that comes with the Universal Gun Assembly is suitable for a range of different barrel diameters.
This page describes the creation of a plastic clamp, in various sizes, suitable for 3D printing. The files used for the clamps shown here are available at the end of the page.
Try a web search for a local "makers" or "hacker space" group in your nearest town/city if you don't know anyone with a 3D printer. They will probably have access to a 3D printer and someone will be happy to "tweak" the drawings for your individual gun.
Warning: making things becomes addictive - but 3D printing is fairly slow - the UGA clamp for 20mm barrels (12g) took about 1 hour 45 minutes to print at standard quality - the Picatinny/NATO clamp took about 1 hour 30 minutes. You will have time for a cup of tea and a biscuit!
Many rifles and pistols have a Picatinny/NATO rail for accessories so we have included a suitable clamp.
Besides a 3D printed clamp you will need an M4 x 20mm countersunk Pozi machine screw and nut. Try a web search for "m4 x 20mm countersunk pozi black".
Design process
The drawings below was done with the free SketchUp Make program. These instructions assume basic CAD drawing skills.
We will also be drawing a clamp that will fit a Picatinny/NATO rail whose dimensions are shown in the drawing below.
The UGA has an outside diameter (OD) of 25mm and the plastic wall thickness is 2mm so we need an outer circle with a radius of 14,5mm.
Start with an 8mm x 15.6mm rectangle with a vertical construction line through its centre. Draw a 14.5mm circle from one of the bottom corners and use the point where it intersects the vertical construction line to draw another 14.5mm circle.
Delete the first construction circle and draw an inner diameter (ID) circle of 12.5mm and complete the drawing as shown below. The centre of the clamp is left open so it will compress as the screw and nut are tightened.
This will be the basic part used to construct drawings for different clamps.
Copy the basic part and use the same circle construction method to draw a circle with 12mm OD and 10mm ID.
The top of this circle must be left open so it will clip to the barrel - an angle of about 40 degrees from the centre and above the centre line will be sufficient.
Copy the basic part and use the same method to produce a drawing for use with a .410. The OD will be 9mm and the ID will be 7mm. Adjustments must be made so the .410 barrel doesn't touch the 4mm screw.
To make the clamp to fit a Picatinny/NATO rail we copy our basic part and place the Picatinny/NATO part on top.
Draw construction lines around the part offset by 2mm - the thickness of our plastic.
Complete the part and remove unwanted areas and construction lines. Note: our clamp doesn't require recoil lugs!
Once drawn the parts should be pulled ("extruded") to a length of 33mm.
On one side of each part create a central hole with an OD of 4.2mm for the M4 screw.
To provide for the head of the Pozi screw a countersink is required - so use the scale function to open up the top of the hole to an OD of 7.5mm
On the other side create a central hole with an OD of 4.2mm for the M4 screw.
Create a 1mm deep hexagonal hole to keep the nut in place. This should allow for 7mm between faces.
Save the file in .STL format (Stereo Lithography) and it is ready to be loaded into the 3D printing software. We recommend the free version of Cura for this.
White PLA material was used for the clamps shown here and they were printed on a Creality CR-10 V3 3D printer.
If you fancy getting into 3D printing yourself, this is a good place to start and learning to use SketchUp is great fun - simply do a web search for "sketchup tutorials".
The photo below shows a set of clamps (.410, 12g, Picatinny/NATO) being printed.
Files available
Please click here for the SketchUp model shown above.
Please click here for the STL file for a 20mm barrel (12g).
Please click here for the STL file for a 14mm barrel (.410).
Please click here for the STL file for a clamp to fit a Picatinny/NATO rail.