For those living in/near central New Jersey I found Dewitt Brothers Tool Company in Kenilworth has the 18mmx1.50 tapered tap for $12 and the 21/32" drill bit for $9. Since we're tapping aluminum I went with a 41/64" bit since the aluminum will flex slightly and be a tighter fit than using the 21/32" bit.

BTW, I've only seen one or two posts referencing the rings/washers "007603-018101 Ring, General, Metal". These appear to be 18mm asbestos filled copper rings. Are these rings really needed?

__________________
Tony
(Actually, a member since 2000)