[A 986 S]

Cutting the slot after turning the knob could be problematic. There a couple of other options that might work. The first would be to drill a series of 7mm holes in the base of the blank to create a 7mm by 17mm slot. This would be easier to do and less likely to blow out the side of the turning if done before turning the knob. A shift arm shaped wooden piece could be inserted into this slot so that you would have a center when turning the knob. After completing the turning the filler piece could be removed and the knob installed on your car.

Another option would be to drill a 17mm hole in the blank (or the completed turning) then turn a cylinder that would completely fill this hole. Cutting a 7mm thick slice down the length of this cylinder would leave you with two half round pieces that could be glued on opposite sides of the hole leaving a slot just wide enough for the shift arm.

The shift pattern medallion that I used came from eBay. I think it was labeled to fit a VW of some sort.

Good luck with your turning and be sure to post pictures of you completed project!