Hole for 1" npt pipe

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Forum topic by greatview posted 07-10-2012 07:22 PM 3003 views 0 times favorited 9 replies Add to Favorites Watch
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133 posts in 3355 days

07-10-2012 07:22 PM

Topic tags/keywords: question drill-driver

I need to drill a 1.050 diameter hole about 8” deep in the end of a pressure treated 4×4. There’s a piece of 1” pipe imbedded in concrete on which I have to put the 4×4. Not my design but I’m stuck with it.
So, I need a drill 1.050 in diameter. I don’t think I can grind down a spade bit as I have to have a close fit.
An option may be to drill oversized and fill with Bondo or something similar.

Any thoughts?

-- Tom, New London, NH

9 replies so far

View HalDougherty's profile


1820 posts in 3435 days

#1 posted 07-10-2012 07:40 PM

I think you’ve answered your own question. I’d drill the hole with a 1 1/8” spade bit and fill it with sawdust & epoxy. If you don’t fill the center of the pipe, it won’t take very much epoxy to make a solid joint around the pipe. I would think bondo would also work. A spade bit may wobble enough to make a 1” hole 0.05 larger anyway. That’s only 3.2/64ths of an inch over 1”.

-- Hal, Tennessee

View Lifesaver2000's profile


556 posts in 3310 days

#2 posted 07-11-2012 03:48 AM

Tom, just to be sure… You said 1” NPT but said it is 1.050 OD. If it is 1” Iron Pipe it is actually 1.315 OD and you should be able to get a tight fit with 1-5/16 drill bit. If it is actually 1.050 then it is a 3/4 pipe if it is Iron Pipe Size (which is what uses NPT).

When I have had to make a hole a bit bigger than the drill bit I have (which seems to happen quite a bit for some reason) I have some kind of rasp type bits that I put in the drill. Not sure how it would work if you have to go all the way through that 4×4 though. I usually am using them on 3/4 inch boards.

View MrUnix's profile


7038 posts in 2397 days

#3 posted 07-11-2012 04:27 AM

If the pipe is threaded, couldn’t you just drill a 1” hole (or whatever size is appropriate for the pipe) and then ‘screw’ the 4×4 onto the pipe? I imagine that even if the pipe isn’t threaded, a slightly undersized hole would still work with the application of a suitably sized mallet :)


-- Brad in FL - In Dog I trust... everything else is questionable

View kizerpea's profile


775 posts in 2565 days

#4 posted 07-11-2012 11:26 AM



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#5 posted 07-11-2012 12:26 PM

If the pipe is still hollow I’d see how far down a piece of rebar goes. Then I’d cut the pipe off and just use the rebar and drill a smaller hole, probably in the half inch range.

View OnlyJustME's profile


1562 posts in 2575 days

#6 posted 07-11-2012 12:42 PM

Drill 1” hole (wiggle the bit around a bit) and use a maul or other heavy object to hit the top of the 4×4 to seat it.
You must be an engineer. My brother is an engineer and over thinks things all the time.

-- In the end, when your life flashes before your eyes, will you like what you see?

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#7 posted 07-11-2012 12:48 PM

+1 for kizerpea

View lieutenantdan's profile


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#8 posted 07-11-2012 01:20 PM

Go easy on us engineers. Use a brake cylinder hone. Won’t take much at all. The hone will expand to the hole size and remove the small amount of material you need.

-- "Of all the things I have lost in life, I miss my mind the most."

View lumberjoe's profile


2899 posts in 2446 days

#9 posted 07-11-2012 01:38 PM

+1 for lieutenantdan. Drill it at an inch and hone out the rest. given this is wood and not metal, I would still go slightly oversized to allow for contraction, especially when something rigid like a steel pipe that will not expand or contract.

I’m not sure what this is for, but perhaps you could find a metal sleeve with an ID of 1.050 and drill the hole in the 2×4 for the external diameter of the metal sleeve.


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