custom shift knob

[Austin David]

I made a better shift knob.  My S3 has little clearance to the dash, I don't care for the metal knob for several reasons.  And I like wood.  With this I'm able to get exactly the size, shape, position, and material I want.

 

The current prototype is made from $5 ash, 1.0 will be black walnut.

 

The process is a little tedious, but I'll share some details for future reference.  Worked with @JohnCh to compare notes.

 

• 3D printed a lot of knobs.  John noted that a 2mm diameter difference has a meaningful change in "hand feel", and I definitely agree.  45mm feels small, 50mm feels big, my "just right is at 47.5mm (before finishing).  Final product is CNC'd in solid wood and hand-finished; details below.
• I personally like a long "neck" or skirt, and I don't like seams.  This is a road car and in Charleston I ride 10 mos / year without gloves. 
• To avoid bulk I dropped the standard brass insert and tapped the wood directly (details below).  Ditto, there is no locknut or set screw -- it attaches and stays "clocked" on with friction, but I may use a little RTV to help manage vibration
• In final installation I'll put a small soft shim under the shift boot, to hold it flush with the lower part of the knob and hide the stick entirely.

 

"final" product, pending my black walnut:

 

 

Production:

• acquire or make a slightly oversized block; 2x2x6" ash, for instance.  Square one end, this is the bottom surface.
• carefully drill an 8mm pilot hole to about the appropriate depth up from the bottom, centered and aligned.  Tap it to 10 x 1.5 or whatever is appropriate.  Drill out the lower part to about 10.5mm (or larger for a different transmission) to accommodate the unthreaded portion of the stick.  I was able to run the pilot on my bench with hand tools, there's some room for error.
• inject liquid CA / superglue to coat the interior threads.  Give it a few minutes, swab it out.  Drying can be accelerated with water and rubbing alcohol.  Do that again for good measure.  When it's dry, run the tap again.
• Make a "sacrificial arbor" with a 10x1.5 bolt by sawing off the head.  Screw in the arbor, fix it in the chuck & align to the bottom surface.  Machine on that arbor.  I ran a pretty gentle process to keep from overstressing the threads, but I think I had a lot of margin for error in here -- there are about 20-30 threads in contact at this point.
• Finish in place, then remove the sacrificial arbor and remount on the stick.  Done!

 

Frustrating limitations:

• I'd like to have machined the bore & threads, but my setup doesn't have enough Z-range to get a bit 2" deep into a 4" part.
• I'd like to have a hidden jam nut, but the threaded inserts & nuts are about 15mm across.  I could maybe machine slightly smaller nuts and inserts, but that's still eating up about 4-5mm of "budget" in a place I'd like to keep small

 

[IamScotticus]

I'll give $20 + shipping 

[Slonie]

I've been eyeing a Built By Basil knob myself, because he'll do the custom shift knob of anyone's dreams, but that's really satisfying to create it yourself. It looks great, bravo!

[Austin David]

I've seen those; his work is amazing.  I actually have a "plan" (parts list) for maple & walnut to match my triple stripe, but I'm waiting until I get the solid walnut before I make more changes.