- Dec 14, 2018
- Reaction score
I used 1/8” drill rod for my first steam engine conrod but am having a struggle to find a die to thread it. The tables show a #5 die as “closest fractional” for 1/8” but that doesn’t seem to exist. All the sets go from 4-40 to 6-32. Mc Master Carr shows 5-40 and 5-44 dies online but none of my local suppliers have them. I am curious as to why there isn’t a 1/8” tap and die given how common the size is and I did see a 1/8” die in some of the sets but it is NPT. Why would you want a 1/8” pipe thread? Ferreting around in my plans book I saw that they called for a 5 BA thread on the 1/8” conrods. So off to Merry old England with my order (through the miracle of Ebay) and a nice little set arrived with the three taps and a die. Some experimenting suggested a #37 drill worked for the taps. The 1/8” rod takes a bit of work but it threaded ok. But the die was quite tight on the rod and I wouldn’t say that 5 BA is exactly right. I doubt that a 5-44 die would be either since the charts show that it is only close to 1/8”. So why all the hassle for 1/8”? Its a very common size, I don’t understand why there wouldn’t be a die size specifically for it.