Plugging a Hole - SAE, NPT, WTH?

Posted By: bulletpruf

Plugging a Hole - SAE, NPT, WTH? - 12/17/12 07:26 PM

Fellas -

So, I need to plug a water pump outlet (for heater hose) in an aluminum water pump. Tapping holes is not something that I do on a regular basis, but I'll bet some of y'all do so I'm asking the experts.

Anyway, the outlet has an ID of .640 and an ID of .880. I'd like to tap it and plug it off with a threaded plug (allen wrench head). I have some plugs and it feels like I could thread one in that's just a tad larger than the ID, but not sure this will be tight enough.

I also have a set of taps and dies, but these are SAE taps (coarse and fine thread). I know that I can use an SAE tap and then thread a bolt inside, but this will look half @$$ed. Can I use an SAE tap and thread a plug into it? Plugs will have NPT threads, right? Just don't know if there is a difference.

Sorry for the 20 questions, but I don't want to mangle this.

Thanks,

Scott

Posted By: Dean_Kuzluzski

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 07:32 PM

NPT is a tapered pipe thread for sealing.

Your stuff is for straight thread.

A GOOD local harware store will have the tap you're looking for.

Bring in a sample to match it up.

Posted By: feets

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 08:09 PM

I'd be wary of plugging it with a plug that fits like a grub screw. Stuffing one of those brass fittings in an aluminum housing rarely ends well. If there's any corrosion you will end up stripping the wrench hole out of that soft brass.
I'd use a plug with a regular bolt style hex head.

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 08:45 PM

Quote:

I'd be wary of plugging it with a plug that fits like a grub screw. Stuffing one of those brass fittings in an aluminum housing rarely ends well. If there's any corrosion you will end up stripping the wrench hole out of that soft brass.
I'd use a plug with a regular bolt style hex head.

Ok, I guess that begs the question - should I use a brass or steel plug?

Thanks,

Scott

Posted By: JohnRR

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 08:46 PM

It's NPT tapped hole , you can purchase an NPT plug with an Allen recess in it , go to your local Vatozone , Advance auto or the like and check the fashion performance aisle

Posted By: RapidRobert

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 08:47 PM

You're talking about internaly plugging an aluminum male heater hose nipple? Yes you'd want to NPT tap it if you do & not sure if there's enough wall thickness to work with (there might be just never looked at it that way). Much easier would be to get a black neoprene end cap from the HELP section at your parts store along with some gasket cement and a hose clamp. You could paint it engine color to try & hide your handiwork. Functionally it'd be fine

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 09:21 PM

Quote:

It's NPT tapped hole , you can purchase an NPT plug with an Allen recess in it , go to your local Vatozone , Advance auto or the like and check the fashion performance aisle

I know where to get NPT plugs, but are you saying that I should just thread it in without tapping it first?

Scott

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 09:26 PM

Quote:

You're talking about internaly plugging an aluminum male heater hose nipple? Yes you'd want to NPT tap it if you do & not sure if there's enough wall thickness to work with (there might be just never looked at it that way). Much easier would be to get a black neoprene end cap from the HELP section at your parts store along with some gasket cement and a hose clamp. You could paint it engine color to try & hide your handiwork. Functionally it'd be fine

OD is .880 and ID is .640, so I have .240 thick wall to work with.

I'm familiar with the hose clamp/rubber plug deal, but this is going on a road racer, and if I spill water on a track (and under my rear wheels), I might end up meeting Mr. Concrete Barrier. So, I want something more permanent. I may put an NPT plug + rubber plug and hose clamp, just to be safe.

Thanks

Scott

Posted By: VincentVega

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 09:29 PM

you have .120 wall thick to work with

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 10:00 PM

Quote:

you have .120 wall thick to work with

Oops, I forgot to divide by 2.

thanks

Posted By: JohnRR

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 10:54 PM

Quote:

Quote:

It's NPT tapped hole , you can purchase an NPT plug with an Allen recess in it , go to your local Vatozone , Advance auto or the like and check the fashion performance aisle

I know where to get NPT plugs, but are you saying that I should just thread it in without tapping it first?

Scott

if it is a tapped hole already , which it should be , why would you feel the need to tap it ??? NPT is a TAPERED thread as stated above so you will see 2 different sizes in the hole ...

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 11:21 PM

Quote:

Quote:

Quote:

It's NPT tapped hole , you can purchase an NPT plug with an Allen recess in it , go to your local Vatozone , Advance auto or the like and check the fashion performance aisle

I know where to get NPT plugs, but are you saying that I should just thread it in without tapping it first?

Scott

if it is a tapped hole already , which it should be , why would you feel the need to tap it ??? NPT is a TAPERED thread as stated above so you will see 2 different sizes in the hole ...

No, it's not tapped already.

Posted By: JohnRR

Re: Plugging a Hole - SAE, NPT, WTH? - 12/17/12 11:26 PM

Quote:

Quote:

Quote:

Quote:

It's NPT tapped hole , you can purchase an NPT plug with an Allen recess in it , go to your local Vatozone , Advance auto or the like and check the fashion performance aisle

I know where to get NPT plugs, but are you saying that I should just thread it in without tapping it first?

Scott

if it is a tapped hole already , which it should be , why would you feel the need to tap it ??? NPT is a TAPERED thread as stated above so you will see 2 different sizes in the hole ...

No, it's not tapped already.

Ok I'll ask the REALLY DUMB question , WHAT is this pump for ???

If it's not tapped and you want to tap it with SAE you can BUT you need to drill the taper out of the hole to the proper size for the thread you want to make it or you risk breaking the tap, or the casting , or both.

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/18/12 03:32 AM

Quote:

Quote:

Quote:

Quote:

Quote:

It's NPT tapped hole , you can purchase an NPT plug with an Allen recess in it , go to your local Vatozone , Advance auto or the like and check the fashion performance aisle

I know where to get NPT plugs, but are you saying that I should just thread it in without tapping it first?

Scott

if it is a tapped hole already , which it should be , why would you feel the need to tap it ??? NPT is a TAPERED thread as stated above so you will see 2 different sizes in the hole ...

No, it's not tapped already.

Ok I'll ask the REALLY DUMB question , WHAT is this pump for ???

If it's not tapped and you want to tap it with SAE you can BUT you need to drill the taper out of the hole to the proper size for the thread you want to make it or you risk breaking the tap, or the casting , or both.

It's a heater hose nipple on an aluminum water pump mounted on a 500 hp 401 AMC in a 71 Javelin street/road race car.

Posted By: ahy

Re: Plugging a Hole - SAE, NPT, WTH? - 12/18/12 03:55 AM

Originally a press in heater nipple I guess. Some Ford pumps are like that. Sounds like you need the smallest pipe plug tap (tapered NPT) that will cut threads plus the pipe plug of your choice. Drill out only if needed. As several have stated, a good hardware store will have the taps, home improvement stores have the smaller sizes as well.

HF (gasp!) has pipe tap sets with sizes 1/4" up to 1 1/4". I have one and for my occasional light use it is fine. I actually needed the 1 1/4" and nobody else in town had it. The taps should indicate proper drill size if needed. Cost is reasonable.

Posted By: Cab_Burge

Re: Plugging a Hole - SAE, NPT, WTH? - 12/18/12 07:48 AM

I would tap it for the next size up from what you have to National Pipe Thread and use a aluminum anadised allen head NPT plug, Summit carrys them

Posted By: runinonmt

Re: Plugging a Hole - SAE, NPT, WTH? - 12/18/12 04:00 PM

Now we have a grasp of what you need. If you're doing track days security is your concern. Ream(not absolutely necessary but I recommend it) then Tap the nipple NPT and use a tapered pipe plug with pipe dope(hardware item). Personally, I would cut the nipple close to the water pump before I tapped it. If you're lucky the local hardware will loan the tap and reamer to you. If not check with a machine shop. I believe you will need to tap it 1/2" NPT,3/8 is likely too small. Your hardware will have a plug in the material of your choosing. I recommend brass.
Ron

Posted By: bulletpruf

Re: Plugging a Hole - SAE, NPT, WTH? - 12/22/12 09:50 PM

Quote:

Now we have a grasp of what you need. If you're doing track days security is your concern. Ream(not absolutely necessary but I recommend it) then Tap the nipple NPT and use a tapered pipe plug with pipe dope(hardware item). Personally, I would cut the nipple close to the water pump before I tapped it. If you're lucky the local hardware will loan the tap and reamer to you. If not check with a machine shop. I believe you will need to tap it 1/2" NPT,3/8 is likely too small. Your hardware will have a plug in the material of your choosing. I recommend brass.
Ron

That's pretty much what I did. I didn't ream it. Got a 3/8" NPT tap and a brass 3/8" NPT plug. Used some Gasoila sealant.

Before picture of what I was plugging.

During.

Then I used a shop vac to clean out the debris and ended up with this.

Hole plugged.

Then I used one of these.

And ended up with this.

And a little closer to being finished with this.

Thanks for all the input.

Scott

Posted By: 6PakBee

Re: Plugging a Hole - SAE, NPT, WTH? - 12/23/12 03:33 PM

I'm curious, why did you feel it necessary to put the rubber cap over the plug. And that looks suspiciously like an AMC. 401?