Great tap, I now have 3 of them in barrels but this last one is only time I have had to drill the hole in the barrel. I got the 18-22mm thread tap so either a 20 or 21 mm hole saw will work. I used a 21mm hole saw so the tap would screw it further although it's still only a bit over half way into the barrel. The nut other tap handle tends to work loose, keep an eye on it, tightening the nut makes the tap to hard to use, so I will try some locktite and finger tight to see if that works. Overall very good quality and one of only a few tapered thread barrel Taps available.
