I need to tap the tuner toys tee fitting for another 1/8 npt fitting for my oil pressure guage.
1. would this weaken the tee fitting too much?
2. what drill bit do I need to use to drill the suckah? I have an npt 27 tap, will that do the tapering for me, or is there a special bit I need to use?

 

When you bought the Tap it had the drill bit size on the package. But if you have a drill index you can take the tap and find the bit that the tap fits closest to.


Tim

 

why dont you just add another t at the firewall somewhere.

 

Well, I bought the tap in a large set, and it doesn't include the bit size. Also, I don't have a drill index, I guess I need to get one. Does anyone know off the top of their head what bit size to use?

Also, if I do use a drill index, do I need to go one step down in diameter to give the threads something to cut? I am new to the whole tap and die thing.

 

I am trying to learn to use my tap and die set, and this will be a big accomplishment for me.

 

You'll need a letter "R" drill bit or a metric bit 8.70mm.

 

thank you very much.

 

I wouldn't drill that fitting. Chances are it's gonna get fucked up, and getting another tee fitting would be so much easier. If you want to practice threading stuff, use a fine wood. That's how I learned. (IMO)

 

yeah, i already bought an npt tee anyways, after looking at the tuner toys, I decided against drilling even more material out of it.

Fine wood is a good idea, I think I will do that.

thanks

 

to tap a pipe thread you need the proper size bit which i think the guy mentioned above and also a tapered reamer. pipe thread is tapered. you also need to tap to a specific depth. look for a student machinist guide or even better a book called the machinerys handbook. it will have all of this and alot more in it. its expensive at $100 though. a students guide will have the basics and will be much cheaper maybe about $30 or so. check your local book store for this.