I made this tool at Techshop SJ.
Step 1: Parts and Tools
- 13/16 " spark plug socket
- Angle grinder
- Angle grinder Abrasive wheel
- Dremel tool
- Dremel grinding stone
- (Optional) Vertical Mill
- (Optional) 1/4" Carbide End Mill
Step 2: Getting the Rough Shape
Use the angle grinder and abrasive wheel to remove the material in between were the teeth need to be. Make each tooth to be about 6 mm wide +/- .5 mm. The teeth should be about 7 mm tall at this point.
This step does not need to be perfect, as I am going to go back and get it to a more precise shape with the dremel tool.
Step 3: Getting More Precise
Also, the teeth will need to be ground down to be thinner so that inside diameter of the teeth will be slightly bigger. Otherwise, it will not fit properly on the oil filter nut. I took out about half of the material in the thickness of the teeth.
You should now have a tool that fits on the nut, although it may not look real pretty.
Step 4: Getting It Even More Precise (Optional)
I used a 1/4" carbide end mill, although anything up to about 3/8" should work. I used the mill around the teeth to give them straight edges.
Be careful with your speeds and feeds. If you get these too far off, you could dull or break your end mill. I used this handy calculator to figure out mine.