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Tractor Talk Discussion Forum

1/2 npt pipe plug what size drill bit???????

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BUDD

01-19-2008 06:37:16




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I need to install a 1/2 npt pipe plug into cast aluminum. What size drill bit do I need to use?

Thanks for the help

BUDD




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Tinker In TN

01-19-2008 15:15:55




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
If you want to be precise, the 23/32 would probably be the way to go. But, you CAN get by with a 3/8 drill bit. I've done it. 3/8 would be 24/32, which is only 1/32 of an inch larger. A pipe tap is tapered, which means that the tap gets larger as you screw it in the hole. So, you have to screw it in just a little deeper, when cutting the threads. So, the question is, how precise does this have to be?

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teddy52food

01-19-2008 10:29:37




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
If you have a female fitting use a bit that just goes in. Try it in a thin piece of scrap iron first.



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Vito

01-19-2008 10:18:46




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
The size is 45/64 as the gentleman already stated.
Vito



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gene bender

01-19-2008 08:29:29




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
Be sure to use a tool to taper the start of the hole to get threads straight and it sure will help starting the tap. I have a 60deg tool in the drill press does great.



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ScottyHOMEy

01-19-2008 10:04:47




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to gene bender, 01-19-2008 08:29:29  
I can think of a couple times that trick would have saved me a headache or two!

Thanks, Gene.



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El Toro

01-19-2008 07:41:44




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
If you're needing to know the tap drill size for 1/2'pipe is 23/32 that's been suggested. Hal



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ScottyHOMEy

01-19-2008 07:37:53




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
23/32"

Here's a link



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671DKS

01-19-2008 07:19:28




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
well for 1/2-14 the size would be a 45/64 drill or size .703 as you are using dissimilar metals make sure you use some anti-sieze on those threads as well. will help in dissasembly later on if needed.



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671DKS

01-19-2008 07:24:18




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to 671DKS, 01-19-2008 07:19:28  
checked another site and it said use the 23/32 I don't know that it would matter much as you have a plus or minus with a gauge because of the taper. in other wise it depends on how deep you tap it. deeper makes the threads bigger the more shallow you tap makes a smaller hole.



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El Toro

01-19-2008 06:54:18




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
The outside diameter of a 1/2" pipe plug is .840"
a 7/8 drill will be.875" in diameter. There's probably fractional drills that will be closer to the .840". Hal



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Eric in IL

01-19-2008 06:46:32




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 Re: 1/2 npt pipe plug what size drill bit??????? in reply to BUDD, 01-19-2008 06:37:16  
23/32



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