Bit Driver Ring (3D Printed, Wearable Hex Bit Driver)

This was a project I started to brush up on my Fusion 360 skills. I didn't have much free time while finishing up my degree, so I was feeling out-of-practice. My goal for the project was to create a piece of functional jewelry. We typically think of it as just decoration, and I wanted to contradict this. I chose to work on a ring for two reasons, the first being that I had less freedom than I would with, say, a necklace; I wanted the added challenge of working within constraints. The second reason was that people work with their hands, and rings are the most present form of hand jewelry. Creating a ring that also functions as a tool bridges the gap between decoration and function.

I printed the ring first in Shapeways' Versatile Plastic (polyamide), and then again in aluminum. Both were strong enough to handle light loading (i.e. unscrewing light switch plates) and the aluminum was able to handle more heavy-duty work (taking apart my amplifier). Overall, I'm really happy with the strength of the prints!

Step 1: Use

- The ring is fairly straightforward to use. Remove the cover, insert the bit, and you're good to go! The cover can be used to hold bits, screws, or other small magnetic pieces you need for your projects.

- I found that holding the ring near the base of the crown allowed me to apply the most torque (without worrying about damaging the band on the plastic ring).

- You can also slide the ring forward between your first and second knuckles and drive screws by turning your wrist, as shown in Image 7.

Step 2: What You Need

Supplies:

- 3 mm diameter, ~1.5 mm deep neodymium magnets (x7)

- Super Glue gel adhesive (using the gel type lets you avoid drips)

Tools:

- 3D printer or printing service (I had my ring printed by Shapeways because I wanted to make it out of metal; I chose aluminum rather than steel since it has better dimensional accuracy)

- CAD software (I used Fusion 360)

- Sandpaper (I used 120, 220, and 400-grit)

- Small files

Step 3: Prototyping

I started out with rough hand sketches, and then created my top four designs in Fusion 360. Next, I printed them using an Ender 3 so I could get a feel for them in 3D. I eventually settled on the design in Image 5 as my favorite. If you happen to wear a size 9 ring, you can download the .STL files I've attached below. If not, read on and I'll walk you through what I did!

Step 4: Sketch the Profile

Before you start this step, I recommend spending some time brainstorming and sketching out your design on paper if you want your ring to look different from mine. It makes it easier to have a rough idea of what you want to achieve before diving into CAD. Also, please note that all dimensions were selected for a ring in my size; feel free to change things up if the proportions look off to you. With that being said, let’s get started!

- Image 1: Create a new sketch (CREATE ➡ Create Sketch). Once you are in the SKETCH workspace, begin with two circles (CREATE ➡ Center Diameter Circle). Make the first circle’s diameter match your ring size. Size the second circle according to:

(circle diameter) = (your ring size in mm) + 2 x (the band thickness you want)

I wanted a 2 mm band, so my second circle was 18.9 + (2 x 4) = 22.9 mm. Make sure the circles are centered on the plane!

- Image 2: Sketch a line that is the height you want the "crown" to be (CREATE ➡ Line). In order to effectively drive the bit, I recommend at least 4 mm. I found 5 mm was a good balance between function and aesthetic. Then, determine the maximum width you want the crown to be. I chose 16 mm.

- Image 3: Sketch a 2 mm line on top of the last line; more on this later! You’ll need it if you choose to make a cover for the ring. Sketch a long line perpendicular to this line; it doesn’t matter too much how long it is, as long as it is longer than the maximum width of the crown.

- Image 4: Sketch a line starting from one end of your “crown” line and drag it down until it intersects the outer circle at a tangent point. This is indicated by a blue circle with a bar across the top. We will call these the “tangent lines”.

- Image 5: Repeat at the other end of the crown line. Add a construction line between the intersection points of the tangent lines and the outer circle. This is done by sketching a regular line, selecting it, and pressing the “x” key on your keyboard.

- Image 6: Extend the tangent lines until they cross the long line you made earlier. I did this by creating a new line from the end of the tangent lines. Make sure the extensions are parallel; this is indicated by blue parallel lines intersecting both the extensions and the original lines.

- Image 7: Once your sketch resembles Image 7, use the Trim tool (MODIFY ➡ Trim) to get rid of the "extra" line sections.

- Image 8: Your final sketch should resemble Image 8. Go ahead and press FINISH SKETCH.

Step 5: Shape the Crown

- Image 1: Create a new plane with the Plane at Angle tool (CONSTRUCT ➡ Plane at Angle) that passes through the “crown” line and is perpendicular to it.

- Image 2: Create a new Sketch on this plane. This will be where you sketch the top face of your crown. Go ahead and choose a shape; feel free to play around and go through a few iterations. I eventually chose a hexagon, because I wanted my ring to recall the shape of the bit (CREATE ➡ Polygon ➡ Inscribed Polygon).

- Image 3: Now, we will create the hexagon for the extruded socket which holds the bit. It is important to note that the size you use depends on the accuracy of your printer. We want to aim for about 0.15 mm difference between the size of the bit and the size of the socket in the actual print. However, due to printer tolerances, a 0.15 mm difference in CAD may actually only be 0.05 mm in the print. In this case, you would want to make the socket 0.25 mm larger than the size of the bit. Because of this, I recommend testing your printer before going to deep into the design process. Since I used Shapeways to print my parts, I wasn’t too concerned about dimensional inaccuracies.

The size of a standard bit is 1/4”, or 6.35 mm. Thus, I created a circumscribed hexagon defined by a diameter of 6.5 mm (CREATE ➡ Polygon ➡ Circumscribed Polygon).

- Image 4: Now, we create two more hexagons that will be used to create a surface emboss later. I chose to space them 1.25 mm apart, but it’s all a matter of personal preference! Go ahead and press FINISH SKETCH.

- Image 5: Create another plane with the Offset Plane tool, offset 5 mm below the one we made earlier (CONSTRUCT ➡ Offset Plane). Create a Sketch on the plane.

- Image 6: Sketch a line out to one of the tangent lines from the vertical line we used to define the height of the crown in the previous step, and record its length. For me, it was 9.332 mm.

- Image 7: Create an inscribed polygon with a radius equal to the length of that line. Select FINISH SKETCH.

- Image 8: Use the Loft tool to join the two sketches (CREATE ➡ Loft). This is the body of the crown.

Step 6: Build the Band - Part 1

- Image 1: Create a new plane through the construction line joining the tangent lines to the outside circle with the Tangent Plane tool. Create a Sketch on this plane.

- Image 2: Create an ellipse that spans the length of the construction line. For the second axis, I arbitrarily selected 11.5 mm. This will determine the curvature of the outside of the band. For a sharper curve, choose a smaller value for the second axis. For a softer curve, choose a larger value. Press FINISH SKETCH.

- Image 3: Use the Loft tool to join the sketch you just made to the bottom of the crown.

- Image 4: Use the Extrude tool (CREATE ➡ Extrude) to cut out the center of the band. Select the inner circle you sketched back in Step 4 as the cutting profile. Use a symmetric profile to cut out both sides at once.

- Image 5: You will be left with a body similar to the one shown here.

Step 7: Build the Band - Part 2

- Image 1: Now, we will build the bottom half of the band. Start by creating a new Sketch. If you centered your very first sketch on the plane back when we were creating the ring’s profile, you can simply create the new sketch on the plane that divides the body in two symmetric halves.

- Image 2: Make sure the ring’s profile sketch is visible. Sketch a line from the center of the ring down to the bottom of the circle that defines the outside of the band.

- Image 3: Draw a line up from the bottom of that line with a length that is half the thickness you want for the band. I wanted my band to be 2 mm thick, so I drew a 1 mm line. Sketch an ellipse centered at that line, with a minor axis the thickness of your band and a major axis that is double the thickness.

- Image 4: Create a 3-point rectangle that bounds the top half of the ellipse (CREATE ➡ Rectangle ➡ 3-Point Rectangle).

- Image 5: You will use the Loft tool to finish the band. First, you need to add two guide rails. Create a new Sketch on the same plane as the ring’s profile. The top half of the ring looks like an arch with two distinct “bases”. Join one of the bases to the rectangle you just sketched by "tracing" the curvature of the circle that defines the inside of the band with a 3-point arc (CREATE ➡ Arc ➡ 3-Point Arc). Repeat for the other base. The right-side rail is highlighted in bright blue, but both are shown here.

- Image 6: Now, we can use the Loft tool to finish the band. This must be done in two steps; once for each base of the arch. Start by selecting the ellipse and rectangle you created earlier; these will be the first profile. Then, select one base as the second profile. Finally, select the corresponding guide rail.

- Image 7: Create another Loft. This time, select the other base and guide rail.

- Image 8: This part is optional, but I like how it looks. Use the Chamfer tool (MODIFY ➡ Chamfer) to bevel the edges of the band. I chose a chamfer of 0.75 mm.

Step 8: Construct the Driver

- Image 1: Use the Extrude tool (CREATE ➡ Extrude) to extrude-cut the socket for the bit that we sketched back in Step 5. I found that extruding 7 mm was enough to ensure a clean cut through the entire crown.

- Image 2: You can also use Extrude to create the surface emboss. I found that a 1 mm extrusion worked well.

- Image 3: We can now create a hole to hold one of our magnets. This will help keep the bit in place until we start applying torque to the driver. Start by creating a Sketch on one of the inner faces of the bit socket.

- Image 4: We want to make sure that there won’t be any interference between the surface emboss and the magnet hole. I found that, for a 3.15 mm diameter magnet hole*, centering the hole 3 mm below the surface of the crown was sufficient.

*I chose 3.15 mm since the magnets had a diameter of 3 mm, and I was planning to glue them in place rather than press-fit. Recall that, due to differences in printer tolerances, you may want to increase or decrease the hole diameter.

- Image 5: Use the Extrude tool to make a 1.7875 mm deep hole**.

**The magnets had a depth of 1.5875 mm, so I added 0.2 mm to account for any dimensional inaccuracies and to leave space for the glue.

Step 9: Make the Cover

- Image 1: Use the Plane at Angle tool to create a plane that passes through the top-most line from your profile sketch and is perpendicular to it.

- Image 2: Create a Sketch on the plane. Sketch an inscribed hexagon that is bounded by a circle with a diameter the same as the top line from your profile sketch. For me, that was 7.467 mm. Go ahead and press FINISH SKETCH.

- Image 3: Use Loft to join this new sketch to the top of your ring. It is important that the sketch you created back in Step 5 to define the top face of the crown is visible. Otherwise, the loft won’t be able to join your sketch to the crown.

- Image 4: Use the Split tool (MODIFY ➡ Split Body) to separate this new feature from the body of the ring. Make the split along the first plane you created in Step 5, back when you were shaping the crown.

- Image 5: This leaves you with two bodies. Move the second body (which will become the cover) up and away from the first (by about 10 mm).

- Image 6: Create a Sketch on the bottom face of the “cover” body. Sketch a circumscribed hexagon that is centered on the face and is defined by a 6.35 mm-diameter circle (which corresponds to the size of a standard bit).

- Image 7: Extrude the hexagon outwards by 5 mm.

- Image 8: Chamfer the edges of the hexagon to make it easier to insert. I chose a 0.75 mm chamfer.

Step 10: Add Magnet Holes

- Image 1: Start by creating a Sketch on one face of the extruded hexagon. We’ll use this to create a hole for a magnet that will help hold the cover in place.

- Image 2: Draw a 3 mm line down the center of the face, starting at the top. Sketch a 3.15 mm diameter circle* centered at the end of this line. Go ahead and click FINISH SKETCH.

*Recall that I chose 3.15 mm since the magnets had a diameter of 3 mm, and I was planning to glue them in place rather than press-fit. You may want to increase or decrease the diameter in response to your printer’s tolerances.

- Image 3: Use the Extrude tool to make a 1.7875 mm deep hole** with this circle.

**The magnets had a depth of 1.5875 mm, so I added 0.2 mm to account for any dimensional inaccuracies and to leave space for the glue.

- Image 4: Edit the Sketch you created in the previous step that defines the extruded hexagon. We want to create 5 magnet holes; these will be used to hold bits, screws, etc. to the top of the ring. I chose to use 5 rather than 6 magnets because I wanted it to be easy to check which part of the cover corresponded to the magnet used to hold it in place while wearing it. If you’d rather use 6, go ahead!

- Image 5: Sketch 1.4 mm lines perpendicular to 5 (or all 6) faces of the extruded hexagon, and then sketch 3.15 mm diameter circles centered at the end of each line. I didn’t sketch a circle beside the face with the magnet hole we created earlier.

- Image 6: Use the Extrude tool to make cuts in two directions (under “Direction” in the EXTRUDE dialog box, select “Two Sides”). In the direction AWAY from the top of the cover, make a 5 mm extrude cut. This creates “channels” that make it possible to install the magnets.

- Image 7: In the direction TOWARDS the top of the cover, make a 1.7875 mm extrude cut. This creates the holes for the magnets.

Step 11: Print & Clean

- Generate .STL files of your model (or download the ones I provided).

- Print the files. Unfortunately I didn't do the printing myself, so I can't speak to the specific conditions used. However, if you have the time I would recommend using 0.1 mm (or less) layer thicknesses and at least 50% infill since you will be applying a fair bit of torque to the ring.

- Remove any supports and excess material from the prints. Since I used a 3D printing service, this was done for me.

- Make sure that bits fit into the bit socket. If they don't, use the files to increase the size of the socket.

- If necessary, sand the prints smooth. Starting with 120-grit paper, sand in a circular motion. The lower grit paper is used to remove the "layer lines" from printing. Move on to higher-grit sandpaper, and continue sanding until you're happy with the surface finish. I actually liked the rough appearance of the printed aluminum, so I left it as-is.

Step 12: Add the Magnets

- In order to install the magnets, I stuck them to a flathead bit before applying a drop of glue. I then used the bit to push the magnets into the holes.

- When installing the magnets that hold the cover to the ring, I found it helpful to start with the cover. I glued a magnet into the cover, as shown in Image 2. Then I stuck another magnet to it and marked the outside face with Sharpie, as shown in Image 3. This made it easier to install the magnets with the correct polarity; I just had to make sure the face with the mark went into the hole in the ring.

- Glue three of the magnets into alternating holes in the cover. Let the glue dry for an hour. Glue the rest of the magnets in.