Hey all,
Trying to figure out how to take my tapping process in-house. I currently pay a good bit for every shell to get thread milled before heat treat (17-4PH stainless parts) so it would pay off quick if I had a reliable way to do it. However I’m a bit skeptical that using the standard hand taps from Park, VAR, etc will work well to cut brand new threads vs just chasing, but maybe I’m overthinking it.
Anyone doing this with success? Any tips and tricks? Do you use machine power or just tap by hand? I could easily machine my own arbor for the hand tap, or potentially just modify the handles to be machine-guided so it stays straight to the shell.
No CNC on my end so just a good old manual mill as my option.
Appreciate any insight!
As an observation- another (potential) option would be one of the many M47x1.0 straight machine taps that are on ebay and the like. THey all seem cheap, of unknown provenance, and who knows how sharp, but they’re out there:
My reservations around this are mainly that I already own the hand taps for BSA and T47, and having to keep both around and sharpened seems like a waste, and of course their totally unknown quality. I don’t have any experience tapping something this large with a straight flute tap so I’m unclear on if this style would provide meaningful benefit.
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I assume you are trying to cut threads into an LPBF part (and not making 17-4PH BB shells from tube or bar) Do you have access to a lathe? If you do, I would single-point them. I think @DEVLINCC does this and may have advice
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Correct, these are 3D printed parts. Don’t have a lathe easily accessible for this kind of work right now unfortunately which is why I’ve had the print shop do the machining- if I remember right, I saw @DEVLINCC mention he was moving to doing similarly, so I may be off base that this is a good use of time/energy. The parts come in perfect every time, but I’m paying quite a bit per part with no end in sight, so having an option to do it myself is very appealing. Could probably pay off a decent lathe if I make enough bikes 
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Right now my volume is just not worth my time. I could set it up in my lathe and do them but would need to make a jig etc. which is normal but the time it takes and the risk of stuffing it up currently is there. I do need to get a test piece and have a go. The 17-4 heat treated actualy machines really nice, so it definitely is feasible.
That said the Aus$160 I pay to get Protosoon to machine the T47 threads and the main pivot all in one hit on the CNC and is perfect tolerances, means it’s a ball ache I don’t have to do. For me I’m sort of over the whole ‘hand made’ thing and just want to make bikes efficiently. I’m a little tired of being cooped up in the workshop on top of a normal work week. So farming out some process and buying some time back is why I pay the fee.
I’ve found threading smaller sizes, ie M6 and M5 to be really difficult in the 17-4 unless the taps are super sharp etc. normal threading issues really. I can’t imagine hand tapping an M47 thread in 17-4. I would think its an in the mill super slow operation. It may be worth getting a test piece printed, buying the cheap tap and having a go to see where you land. Use lots of lube…….’cause…….you know!
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