In this instructable I make a custom gear shift knob for my toyota Aygo.
There is a build video and the steps that I took
Piece of hardwood approximately 70mmx40mmx60mm - I used a chunk of cherry from an old bed leg.
Some kind of durable finish ( I used crystal clear coat)
CNC - optional but certainly makes the start easier
Dremel or other rotary carving tool
Printer - to print out template
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Step 1: Watch the Build Video - Then Follow the Steps
Step 2: Trace the Skull
Depending on how you are going to proceed, if you have a CNC to make the first pass of cutting then you'll need to convert a black and white image into paths for the cnc.
I used InkScape and it's 'trace bitmap' feature to turn the black and white image into an SVG which I could import into fusion 360, and from there create the gcode to have my CNC carve out the main shape. I did not have it doing the smaller details.
In either case scale the image to the size you intend to make for your gear shifter, and print it out.
Printers can render nicely at 1:1 scale so you wind up with something as a reference template that you can stick to the wood and start carving to.
Step 3: Carve the Face
Either run the job through a cnc, or simply stick the template to the front of the wood and use your rotary tool to work away the material that traces the outline of the skull, and then carve out the eye sockets.
If you print lots of templates you can keep affixing new ones as you work to help pick up the references.
I used a sharp point bit to help me carve out the 'teeth' lines and the nose holes.
I also used a square file to help refine those lines by hand.
Step 4: Drill a Hole to Receive the Gear Stick
It's important to drill at this point whilst you still have a block to clamp.
I drilled my hole just behind the 'teeth' and perhaps 75 percent of the way down to what would be the top of the skull.
Use a bit big enough to take an m8 threaded rod.
Step 5: Create Recess for M8 Nut
Using a chisel, or the dremel, or both, carve out a recess that will take an M8 Nut. This is the size of thread on the end of the toyota aygo gear shifter. If you have a different car you'd need to check how the gear knob is attached and if by threaded rod, what size it is.
Once you've created the recess, epoxy the nut in place.
At this point you can use a short M8 Bolt to help you hold the bloc for the finish shaping.
Step 6: Rough Shape on the Bandsaw
NOTE - Tools, even bandsaws, can be dangerous. You are responsible for your own safety, do not attempt anything you are not comfortable with.
I stood behind my bandsaw and used it to slowly carve away the material leaving me with what I felt was a fairly well skull proportioned object. When I was done it looked like this
Step 7: Sand to Refine the Shape
I used a bench sander, but you could do this by hand with sandpaper. it would just take a little longer. The clsoe you got to a good shape with the previous step, the easier this part is.
I found it best to keep it moving, swirling around in circular motions. if you stop too long in one spot you risk leaving a weird flat spot.
This process will let you get a smooth shape around most of the skull, but some areas can't be reached on a belt sander
Step 8: Final Shaping With Rotary Rool
To blend the features of the sides of the skull around to the sides, and shape the underside of the skull I used a burr bit in a dremel on a fairly low rpm, and just hand carved until I was fairly happy with all of the features
You'll note from the photo my hand is hardly holding the skull, that is because I screwed an m8 bold into the nut and was using that to give me secure grip and control whilst I carved the remaining features.
Then I did a final hand sand ahead of spraying the finish.
Step 9: Spray Finish
This is designed to be something which is handled, so you want a tough finishing coat. I actually used some silicone sanding sealer applied by hand, then finished with several layers of crystal coat spray.
A carboard box is a useful mini spray booth here, and having a bold threaded into the nut can be used to hand the skull from the top of the box. This make it very easy to spray, and turn the skull to get even coatings.
Step 10: Attach Your New Gear Shift Knob!
The toyota aygo's gear knob simply unscrews from the gear stick, there is a length of m8 thread at the top of the shaft.
Just screw your new gear knob in place.
For a manual shift you're probably going to want it to be fairly tight in place, you can use other nuts as spacers to get it tight in the orientation you want it. For my automatic it didn't matter so much.