# Parallel holes on a bowed wall?



## BMcMullin (Jan 5, 2020)

What's the best way to drill a set of perfectly parallel holes on a bowed wall?

I'm installing some large, solid-wood floating shelves by screwing 16" long 1/2" threaded rods into the 2x4 studs and then drilling holes in the backs of the shelves. 

I just realized the wall is slightly bowed from one end of the shelf to the other, with the center coming out proud about 1/4-1/2" compared to the ends. My original plan was just to drill the holes square to the wall, but if I do that at each hole, they'll end up "fanning" slightly away from the center. I think that will make it really hard or impossible to get the shelves onto the rods. 

To make things worse, each shelf is actually two separate pieces (each about 4.5'x16"x1.75"), so if the holes (and rods) aren't parallel, there will be a wedge-shaped gap between the shelves.

I'm sure the rods will have a little bit of flex, but I think it's already going to be a tight fit to get the shelves on the rods, so I want to avoid fighting the rods any more than I have to. And I want to make sure the two pieces line up as well as possible. The holes will be 16" apart (to hit the studs).

Really wish I had checked whether the wall was flat before I got this far🤦‍♂️. One of these days, I'll remember that most builders don't care about getting things really flat or square.


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## TomCT2 (May 16, 2014)

get a long long drill. box stores typically have them in 24-36" length.
use a pc of plywood, set battens at each drill location, +/-1/2" apart.
line it up as you want the back edge of the floating shelf.
use a level to make left-right and front back all plumb, etc.
run the long drill through the batten spaces to drill the studs.

you may require some help/brackets/supports to hold the drill ply jig in place.....


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## GeorgeC (Jul 30, 2008)

I am curious where you will find long rod with wood screw threads on one end.

George


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## Dave McCann (Jun 21, 2020)

GeorgeC said:


> I am curious where you will find long rod with wood screw threads on one end.
> 
> George


This fella used common 1/2-13 threaded rod. Drilled an undersized and threaded the rod into the wood creating threads as it went in. I doubt there is enough outward pull generated to pull the 1/2-13 threads out of the wood stud. The rods shown below are supporting his body weight.


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## BMcMullin (Jan 5, 2020)

TomCT2 said:


> get a long long drill. box stores typically have them in 24-36" length.
> use a pc of plywood, set battens at each drill location, +/-1/2" apart.
> line it up as you want the back edge of the floating shelf.
> use a level to make left-right and front back all plumb, etc.
> ...


That's a great idea! Simple but effective. I've got a perfect 8' strip of scrap plywood. And I should be able to use it to transfer the holes to the back of the shelves. Filling the holes for the temporary brackets isn't a big deal.


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## BMcMullin (Jan 5, 2020)

Dave McCann said:


> This fella used common 1/2-13 threaded rod. Drilled an undersized and threaded the rod into the wood creating threads as it went in. I doubt there is enough outward pull generated to pull the 1/2-13 threads out of the wood stud. The rods shown below are supporting his body weight.
> View attachment 422146


That's where I got the idea for how to do my shelves. I'm doing 3 rods per shelf since I'm using some pretty hefty pieces of wood and they'll be in a playroom, so I assume kids will climb on them at some point. I'm hoping I can do it without creating the special tool he made (I don't have a welder) and I'm going to try skipping the part where he pre-taps the holes since that seems redundant.


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## Dave McCann (Jun 21, 2020)

BMcMullin said:


> That's where I got the idea for how to do my shelves. I'm doing 3 rods per shelf since I'm using some pretty hefty pieces of wood and they'll be in a playroom, so I assume kids will climb on them at some point. I'm hoping I can do it without creating the special tool he made (I don't have a welder) and I'm going to try skipping the part where he pre-taps the holes since that seems redundant.


I might suggest a few trial holes in a test piece, to test for the proper size drilled hole. Too small and either one will not get the rod threaded in to the desired depth or the 2x4 will split. To large of a hole will not provide enough bite for the threads.
I have no opinion on whether using threaded rod is "better" or "worse" than using the hidden shelf brackets which attach against the face of the wall using several wood screws per bracket.


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## FrankC (Aug 24, 2012)

If the shelves are scribed to the wall, then there would be no problem at the joint of the two shelves, I would also dowel the ends of the two shelves together. It should not matter if the rods are not perfectly at right angles, the shelves will move them into position as the shelf is pushed on to them as long as the holes in the shelf and wall are aligned.


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## _Ogre (Feb 1, 2013)

i'd think a slightly oversized hole and a liberal coating of jb weld would do as well and be easier to install


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## Dave McCann (Jun 21, 2020)

_Ogre said:


> i'd think a slightly oversized hole and a liberal coating of jb weld would do as well and be easier to install


I thought about epoxy, then I thought about a remodel. Who knows, maybe 6 months down the road the shelves need moved to another location.


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## danrush (Oct 16, 2017)

We just use plain steel rods for floating shelves. A slightly over sized hole in the stud allows a bit of adjustment if the hole is off slightly. A dab of construction glue on both ends of the rod and the shelf is set. If I'm really worried about the shelf pulling away from the wall, I'll run a small bead along the back of the shelf as I install it. 

Sent from my SM-T580 using Tapatalk


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