3D Printed Threaded Knob
How To Make a 3D Printed Threaded Knob Common Hardware for Inserts.
I have often found the need for different threaded knobs, either with a nut or a bolt, for some of my projects. While these may be available for purchase, it's a lot faster, easier and cheaper to design and print your own. For this project, I designed and 3D printed a set of knobs using 1/4-20 nuts and bolts from my local hardware store.
3D Printed Threaded Knobs
Watch the video to see how I designed, modeled, 3D printed and assembled these useful 3D printed threaded knobs, or read on. All the parts were designed in Fusion360 and printed on the Monoprice Select Mini 3D printer in PLA.
Step 1: Measure Your Hardware
I plan on using these as quick attachments on my workbench to secure different tools, fixtures and other equipment while I'm working; as well as securing the removable top on my sawhorse work table.
I bought several 1/4-20 hex bolts and nuts from my local hardware store. The first step in designing the knobs is to measure the parts. If you don't have a set of calipers, most standard hardware can be found on McMaster.
The standard dimensions are:
Bolt Head Distance Across Flats: 0.432"
Bolt Head Thickness: 0.153"
Bolts Diameter: 0.238" (just use 1/4")
And for the Nut:
Nut Distance Across Flats:0.431"
Nut Thickness: 0.215"
Step 2: Model the Knob Shape and Revolve
The next step is to create the 3D model, and I used the Revolve function in Fusion360. Open the program and start a new component and create a sketch on any of the planes. This knob is designed to be 0.4" thick and have an outside diameter of 1.5" and a clamping surface that is 0.75" in diameter. Remember that when working with a revolved object, the dimensions in the sketch are the radius, not the diameter, so cut those numbers in half. Us the vertical edge of the sketch to create the revolve.
Step 3: Cut Out the Pockets in the Knob
With the solid body created, the next step is to cut out the pockets for the hex-head of the bolt, or nut, and the through hole to accept the threads. Create another sketch on the top surface of the knob, and use the polygon tool to create a hexagon sketch on the surface.
I oversized the distance between the flats to make sure I had an easy fit for the hardware, as well as a space for the epoxy to go when I glued everything together.
Create another sketch on the bottom surface, and cut-out a circular hole big enough to accommodate the threads of the bolt. I used 0.26" to make sure there was an easy fit when screwing the knobs together.
Step 4: Design the Shape
With the critical features of the hex pocket and the through-hole complete, we can move on to the more artistic part. I wanted these knobs to have a unique look, and decided on a 3-lobe, triangular design.
To make this shape on the outside:
Create a sketch on one of the horizontal planes
Draw a circle with the origin on the horizontal axis
Make the circle tangent to the bottom circle
Use the Circular Pattern function to instance the circle around the origin
Exit the sketch and extrude the shapes through the knob
With the final shape complete, add fillets on all the sharp corners to smooth out the print and make a part that's nice and smooth to the touch.
Step 5: 3D Printing
3D printing ... do that. This part is designed so that it can be printed without any support material. The overhang is at 45 degrees, so check the settings in you slicing software.
Step 6: Create the Inserts
Next, lay out some tape on a work surface, and mix the epoxy to hold the hardware into the printed parts. I used a 5-minute epoxy that you mix in 50-50 ratio, using a popsicle stick to mix. Open a window, this stuff is foul smelling.
Don't forget to cut the bottle open...
Spread the epoxy on all six sides of the bolt head, or nut , be careful not to get any on the threads or it will make screwing the knobs together very difficult. Slide the bolt, or nut, into the pocket and leave the assembly somewhere to dry where the hole is facing up. If you don't the epoxy will run out of the hole. I used a beer bottle.
Step 7: The Finished Product
That's it, once the epoxy cures, thread the nut and bolt together. If any epoxy got on the threads, just turn the bolt firmly through the nut to clear it out. I plan on using these knobs to hold together fixtures and jigs on my workbench, but they can easily be modified to create doorknobs, drawer pulls or other handles.