Typically I just use what I have, which is a Craftsman set of small taps and dies, but for the 5-40, 6-40. and 8-40 size taps those are uncommon sizes (8/40 being used in scopes) what I have as options in 5-40 are:
1. Hand Plug tap
2. Bottoming tap
3. Taper Tap
My gut tells me as I am cleaning up thread, would be a bottoming tap, but I seek the wisdom of those who done this before me on what they would prefer?
Thanks!
This company has both the taps, and dies in 5-40, 6-40, & 8-40
https://drillsandcutters.com/search.php?Search=SEARCH&q=5-40+tap
Any of the 5-40 taps work, however the bottoming tap works best. Use tapping fluid.
Buy a quality HSS tap set of all three.
Plug taps start easier than a bottoming tap. I only use bottoming taps if it is a blind hole and I need the thread length. For new threads I start with a starting tap and often run a plug tap to clean up the threads.
For chasing threads I usually use a plug tap beause it is easier to start & most holes are deep enough that they don't have to be cleaned all the way to the bottom. For shallow holes you need a bottom tap so I would get one of each in each size. They are pretty reasonable on ebay. Rudy
Thanks Guy's. Those are some weird costing taps and dies. The 8-40 which is fairly standard in rifle scope mounts is the costliest of the three, which I would think more of them get used then the other two, but I was told they are "special."