Introduction: How to Make the 4th Doctor's Sonic Screw Driver
I've been too busy this year to come up with a new Halloween costume, so I'm revamping (regenerating?) my 4th Doctor costume.
In the past, I've used the 11th Doctor's screwdriver (gasp!) and thought it was time to make the costume more accurate by making Tom Baker's sonic.
This instructable will be covering the 3D modeling (for 3d printing) and another bonus step of turning the base from aluminum using the CAD drawing.
Step 1: CAD Step 1: Drawing the Contour for Revolving
In this instructable will be using Fusion 360 to model the sonic screwdriver.
First, we will create a new document and import an attached canvas using a reference photo. Once that canvas is placed. We can right click the canvas in the browser and choose "calibrate". Then we will be selecting two points that we know the distance (186mm from an educated guess). This step scales your canvas up to the correct size, in order to accurately trace it.
Now that the canvas is properly sized. We will create a new sketch on the same plane as the canvas. From there, start tracing out all of the geometry from the center of the canvas. Small details can be replicated by drawing one, then using the rectangular pattern function.
After half of the sonic has been drawn, exit the sketch, then choose revolve with that sketch selected as the profile. This completes part one of the sonic.
Step 2: CAD Step 2: Modeling an Attachment for the Top Piece
In order for this to print with the best surface finish, I've decided to break the top part away from the base. This also allows me to attach it to an aluminum base that I'll be creating later.
First, we'll create a new sketch on the top of the base piece. I'm using aluminum round stock that already has a 3/8-16 threaded hole in it, but if you are modeling this, you can choose whatever size you want.
Once in the sketch, draw a circle the size of your threading (in my case it is 3/8"). Exit the sketch and extrude that circle down into the base. Then choose "thread" and enter the size thread you want.
Now the inner thread is complete, we'll need to start drawing the top threading and start thinking about how we'll attach the rest of the top components. To get an offset plane directly in the center of the base, we will first create an axis through a cylinder, then once that axis is created, choose plane at an angle. This will give us midplane inside the cylinder.
We will create a new sketch on that plane, drawing half of the contour for the threading, along with a half dome. Exit sketch and revolve this new profile (making sure that your operation is set to new body). Then we can select the bottom cylinder of that new body and add a thread to match the inner thread we created earlier.
Step 3: CAD Step 3: Finishing the Top Piece
OK, things are about to get a little trickier. But stay with me, I'll help you with things that I struggled with at first.
This step is going to involve a lot of offset planes to align our sketches. First we will create a new sketch from that cylinder midplane we created before. Now we will create a new sketch on that plane, draw a 21mm circle with a 2mm offset so the bottom of the circle just barely intersects the threaded dome piece we created earlier.
Exit that sketch and extrude it 5mm with a symmetric selected as the direction and join as the operation type. This new cylinder should now be attached to the threaded dome.
We now will create another plane at an angle using the cylinder midplane as our line selection. Enter the sketch and hit "p" to project geometry onto this sketch. Select the threaded dome. This will give us some sketch elements to place the center piece in the middle of the top part. If we hover over the center of the projected sketch near the center, it will snap to the absolute center. We can draw a line there to find the middle. Then draw some more sketch geometry to form the inside piece. Exit the sketch, and choose revolve once more. This new piece will not be attached to anything yet.
To create the three cylinders that attach the middle piece to the top cylinder, start by creating an offset plane from the top of the base model. Bring it up to just below the surface of that cylinder. Now create a new sketch and draw a circle aligned with the center of the top cylinder. Exit sketch and extrude it to the floating middle piece (change distance "to object" in the menu). All of the top pieces should now be a single body and the base another body and we can add some filets for strength and visual appeal.
In order to replicate that extrusion and filets, choose circular pattern and change type to "features". In the timeline below, select the extrusion and filets created and as the axis, select the top cylinder and set the quantity to 3.
It is kind of a lot to read and if you want to follow along with something other than text and photos, I've got a video on that modeling process.
Of course, if you don't even want to model it, you can download the 3d files on pinshape.
Step 4: Turning the Base From Aluminum
If you want to be extra fancy, you can do what I did and turn the base from aluminum using a drawing from the CAD file we created in the previous steps.
Start by laying out some dimensions on the aluminum stock using a sharpie. Then take your time on the metal lathe getting it as close as your tooling and skill level will allow.
Once the shape is how you want it, you'll want to sand and polish it. Start with a low grit (80-120) to get any deep scratches out. Slowly work your way up as high as you want to go. I stopped at 600 grit then switched to an aluminum polish. Apply this with a scotchbrite pad, then use a paper towel to buff it out. If you sanded all of the scratches out in the previous steps, this will give you a very high polish.
You can see a video of this process along with my final sonic.
Step 5: Assembly
Let's bring all that together now to finish this sonic screw driver.
If you didn't turn the base from aluminum and just printed the whole thing, you will want to give this a quick metallic paint job. While you are at it, throw a little paint on the top piece also to match what the Doctor uses on screen.
If you turned the base from aluminum, you'll want to thread the top of the base to match the 3D printed threading.
Carefully screw the two pieces together and you're done!
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