I got the taps from McMaster - I think they were about ten bucks each. I don't have a #55 drill, so I used the closest I had, which was a #57. However, I don't think that's my issue, since the tap happily threaded the first half of the hole. This hole goes all the way through, and exits sort of halfway into the wall of the casting - so maybe when I drilled it the bit deflected? But I'm not sure that's my issue, since the tap wasn't yet exiting the hole. Admittedly, I'm fairly new to tapping holes, this kit is the first time I've actually had to buy taps, so I may be doing something wrong without realizing it.
What taps do you recommend, and where do you buy them?
