SpudFiles

On that note Brian, I've never used untapered pipe threads. How painful are they to seal?

Except for a few special purpose threads I believe that metric threads are the greatest. You get the size, and coarse or fine. No confusion.

How painful are they to seal?

You just need to get out a roll of PTFE tape.

The BSPT's special purpose is gas fittings

I have tapped brass and steel by hand before. It takes FOREVER, but it works. Also, when using this in a lathe, you will need to be squirting oil on the piece almost constantly right? I had to oil my piece that I was tapping, and I was doing it by hand!

Normally when you tap with a lathe you're turning the lathe by hand or with a power feed, you're going reeeeeeal slow. The best use of the lathe is for getting the work lined up so you're not tapping at an angle. You can tap with a power feed, but you better be ready to slap the engagement handle at the right time.

If you're using a mini lathe, the torque may not be enough to use the power feed, but it still makes a great alignment device.

You just need to get out a roll of PTFE tape.

or use an o-ring but it doesn't work with every joint

How painful are they to seal?

You just need to get out a roll of PTFE tape.

The BSPT's special purpose is gas fittings

I wouldn't bother with PTFE tape on parallel threads, it's a sealing aid and parallel threads aren't meant to form a seal, they just allow you to compress an O-ring or proper bonded seal washer between the 2 pieces.
Liquid thread sealants will work on smaller sizes bur are a sod to get off.
I prefer parallel threads myself, their one weakness is it's very hard to get something tightened at the right orientation with an o-ring or washer.

BSPT is tapered..
BSP is straight.

it's a bit different in the UK, technically tapered fittings should be called BSPT but suppliers don't generally bother and BSP usually means tapered whereas BSPP is used for parallel.

tapping small threads by hand is easy, a lathe is overkill. However anything over 1/2" gets a bit hard to keep it square. I usually start it in the drill press, turning by hand with an extension bar over the chuck key, until its stuck in then take it out and finish with the hand tap.

I like the fact you can thread in fittings from either side or thread in stuff that needs to go in a certain depth.

Tapered doesn't allow for that.

Loctite will fix the leaks.
I think I can still seal about 90 % if not more with just PTFE tape.

Plus I frequently mix the two types..If it doesn't work for some reason I tap or cut both parallel.

I don't really pay attention to tapered threads, I just tighten stuff down hard with a lot of PTFE and it'll seal. Most of the time one will be tapered anyway.