Off Topic: Metal thread taps

[Wife'nHubby]

Sorry for posting an off topic item here but I figured there are lots of knowledgeable persons here who could answer this question:

We are using a 3/8" hex nipple - have to make a hole in a pot, thread this hex nipple in and create a water tight seal. What size drill bit do we use and what size thread tap do we use?

Shari
(who knows nothing about drilling/tapping threads and hubby can't remember)

 

[Ambull]

3/8" NPT? For NPT the threads are tapered, and it is a little different than a 3/8" bolt.

 

[beerman6]

9/16ths drill.

http://www.engineershandbook.com/Tables/npttap.htm

 

[loadthestove]

Take a look at this chart and see if it helps.
http://www.bigblockdart.com/techpages/TapDrillChart.shtml

the top part is for bolts and the bottom is for pipe fittings..

 

[Wife'nHubby]

Ambull-

I am in foreign water here talking about fittings, NPT, etc. so can't answer your question - but - here's link to a picture of what we are working with. Will the picture answer your question so you can answer mine?

http://www.candletech.com/budgetmelter/zoom7471.htm

Shari

 

[beerman6]

umpkin2: 9/16ths drill...

You will need a reduced shank drill.A straight shank will not fit in a 1/2 or 3/8ths chuck.

 

[nomak]

step drill this hole using a smaller diameter drill maybe use two differet size drill working up closer to a 37/64 then use of a pipe reamer will help as well before tapping the whole for that is a pretty good size pipe thread to tap and it will help with tapping and also prevent braking off the tap wich in solid steel will happen if you use even the slightest dull pipe tap. Working in the tool and die trade I know this first hand and taps suck to get out when they break off flush with the surface your tapping and also if its a regular thread tap and its burried in the steel inch or so deep this proves to be a problem as well when removing a broken tap..also pipe tape or pipe dope which ever you prefer helps with seal....good luck and happy tapping..

 

[DSS]

NPT is pipe thread which is different from NC. A 3/8 pipe fitting has pipe thread, a 3/8 bolt has NC/NF thread (coarse or fine).

Pipe thread is tapered, bolts are not. You need pipe thread.

 

[nomak]

umpkin2: 9/16ths drill...

You will need a reduced shank drill.A straight shank will not fit in a 1/2 or 3/8ths chuck.

yes and be very carefull not to let the drill grab if youre using a powerfull drill with lot of torque cause the drill wont break your wrist will or smash your fingers somehow or any number or injuries requiring screaming of profanitys..lol..

 

[loadthestove]

as mentioned pipe threads are different from commom bolt threads because they are tapered.
If I'm understanding your question right,you want to know what size drill bit and tap to use to drill and thread a hole to screw a 3/8 nipple into.

If so use a 37/64 drill bit and use a 3/8 pipe tap.this should make perfect threads to screw the nipple into.

 

[duane9835]

9/16ths drill.

http://www.engineershandbook.com/Tables/npttap.htm

9/16ths. Got it memorized!!! Just had to mill out 2 broken taps out of 17-4SS today:bang: Guy's on 3rd shift do some amazing things sometimes:hmm3grin2orange:

 

[nomak]

as mentioned pipe threads are different from commom bolt threads because they are tapered.
If I'm understanding your question right,you want to know what size drill bit and tap to use to drill and thread a hole to screw a 3/8 nipple into.

If so use a 37/64 drill bit and use a 3/8 pipe tap.this should make perfect threads to screw the nipple into.

you get your drill from a starret drill and tap chart card it works and helps with tapping but I have seen other companies use the 9/16 drill but im looking at a starret card as we type and it recommends a 37/64 as well..the extra steel will help with the sealing of threads but make it a lil more difficult in tapping all in ones preference..

 

[nomak]

9/16ths. Got it memorized!!! Just had to mill out 2 broken taps out of 17-4SS today:bang: Guy's on 3rd shift do some amazing things sometimes:hmm3grin2orange:

go with a 37/64 and use a pipe reamer if u have one available to u .. also good tapping oil and sharp tap.. you will get it..

 

[Steve NW WI]

Note the suggestions above about using oil on the tap...Beleive them. There are specifically formulated cutting oils, but a bit of motor oil or whatever's in the garage will do the trick for the 1 hole you're tapping. Pipe threads are tapered kinda like this \/, so don't try to get the tap all the way into the hole. Start slow, maybe a half dozen turns, check your fitting to see if it screws in, if not go another turn, repeat as needed. It also helps to back the tap out often to clear the metal chips off it.

BTW, 9/16, 37/64, or whatever is a big bit for a hand held drill. Hang on tight, especially when it's almost through. If you've got a drill with good power and aren't hanging on, it'll rip it out of your hands. It helps a lot to clamp whatever you're drilling into a vise as well.

Good luck!

 

[DSS]

Note the suggestions above about using oil on the tap...Beleive them. There are specifically formulated cutting oils, but a bit of motor oil or whatever's in the garage will do the trick for the 1 hole you're tapping. Pipe threads are tapered kinda like this \/, so don't try to get the tap all the way into the hole. Start slow, maybe a half dozen turns, check your fitting to see if it screws in, if not go another turn, repeat as needed. It also helps to back the tap out often to clear the metal chips off it.

BTW, 9/16, 37/64, or whatever is a big bit for a hand held drill. Hang on tight, especially when it's almost through. If you've got a drill with good power and aren't hanging on, it'll rip it out of your hands. It helps a lot to clamp whatever you're drilling into a vise as well.

Good luck!

:agree2:.....what he said.

 

[Wife'nHubby]

Thanks so much, guys! I 'knew' you would know what to use. Hubby has all these tools which he used to use. If I get him going then he remembers and then doesn't forget it later on. We kid around calling this his "Rusty Brain" syndrome. It's kind of like popping the clutch on an old car. He just needs a 'jog' every now and then, & I mean that in the kindest, gentlest of ways.

Talking about strong drills - yup, we have one, twisted my wrists with it this summer a couple of times. We raised sons - I know the language.

Shari

 

[Wife'nHubby]

Is the pot steel? Or aluminum?

How thick is the pot?

It is aluminum.

3/8" thick

Shari

 

[nomak]

It is aluminum.

3/8" thick

Shari

use mineral spirits or wd-40 it will work better in aluminum for it has a tendecy of gumming up on the tap thus messing up the threads....

 

[HillRat]

Hey Shari,

Would something like this work? You still have to drill a decent size hole, but there's no tapping!

http://morebeer.com/view_product/19793/102220/Weldless_Spigot_-_Stainless

Ed

 

[nomak]

Hey Shari,

Would something like this work? You still have to drill a decent size hole, but there's no tapping!

http://morebeer.com/view_product/19793/102220/Weldless_Spigot_-_Stainless

Ed

that might be a better solution since 3/8 on aluminum isn't much thickness to tap and get very many threads into for sealing purposes and also the fact it could strip out easily..