Hack hole extension with threaded rod

[branimal]

I'm trying to fish some mini split lineset up a finished wall from the floor below. The floor below is wide open. I've got a 2 3/4" hole drill thru the bottom plate, but when looking thru the hole, I see I put some blocking b/w the studs in the finished space.

I think I can making a hole saw extension by MIG welding a threaded rod to a hole saw extension bit (I've already hacked this extension for a previous job - see pic).

If a lay the extension (7/16" diameter) and the threaded rod (1/2") on a piece of angle iron they should line up straight. I'll strip the zinc coating off the rod with muriatic acid.

IS this going to work or am I spinning my wheels?

 

[Jim greengo]

I don't like drilling blindly through wood like that,too easy to blow through wires inside of wall.
Do yourself a favor and open an access hole around where you think the fire stop is at.

 

[PCustoms]

Use a properly sized socket to go over the hex on the holesaw. Little tape will hold it on.

Then use whatever combo of 3/8 extensions required. From there you can drive it with a hex to 3/8 drive adapter.

Had to do this to get through rim joist and thick closed cell insulation. There's proper extensions available but for a 1 off this was perfect.

 

[rlitman]

I've extended drill bits like this. I prefer to weld into a piece of aluminum angle, to prevent sticking. I'll grind both pieces to end in a truncated V, weld across one side, then across the other, and then hammer it straight.

edit: If the above didn't make sense, just don't grind to a cone and weld all the way around.

 

[The Cobbler]

Use a properly sized socket to go over the hex on the holesaw. Little tape will hold it on.

Then use whatever combo of 3/8 extensions required. From there you can drive it with a hex to 3/8 drive adapter.

Had to do this to get through rim joist and thick closed cell insulation. There's proper extensions available but for a 1 off this was perfect.

I'd be leery of that set up in a wall, recipe for loosing your stuff .
I have 2 extensions made from 1/2" schedule 40 water pipe , 4-1/2' each (totals 9') that I made for a job many years ago to drill vent pipes from the basement to the attic without doing damage to any main floor exterior walls when I was installing basement bathrooms . I have used them quite a bit actually .
There's a funny story attached to this set up. I might share it later . it's a long post but its in reference to this post from @Jim greengo

I don't like drilling blindly through wood like that,too easy to blow through wires inside of wall.
Do yourself a favor and open an access hole around where you think the fire stop is at.

 

[rust in the eye]

I don't think flex auger bits come large enough for a line set.
Is the finished wall drywall? Unless it's a fancy finish why not just open up the wall and cut through or remove the blocking?
Patching a bit of drywall seems easier than cobbling together something that may or may not work..

 

[The Cobbler]

I have move blocking out of the way for return air etc by cutting a 2x4 or whatever to lenght & a hydraulic jack to jack it out of the way .
place it on one end of the blocking and jack it up. once you free the nails it's pretty easy to move it up & out of the way

 

[PugetDude]

I just made a 6' long extension out of a piece of heavy wall Chrome-moly tube. Welded a 3/8" NF Grade 8 bolt on one end for an old 1/4" Jacobs chuck, and a piece of 1/2" diameter cold rolled steel on the drive end.
We used a spade bit and drilled a 1-1/4" diameter hole (big enough for the chuck to pass through) through a stucco exterior wall, interior drywall, and the kickspace plywood of three kitchen cabinets. Came out within 1/4" of our intended target. Slid a 1/2" black iron pipe into the hole for propane service. Now his wife can have her commercial gas range in a house with no gas service available.

I don't think I took any pictures, maybe my friend did.

Edit:
Here's how I lined the pieces up for welding; used appropriate diameter drill bits as spacers.

Other end:

 

[seber]

Using a tube with an ID that matches the hole saw shank will make the job pretty simple.

 

[lardy1]

I'd open the wall. Patching drywall isn't that hard and no surprises.

 

[PugetDude]

I'd open the wall. Patching drywall isn't that hard and no surprises.

Full disclosure... in this case I had installed the cabinets last summer so I knew there weren't any surprises lurking in the kickspace. I also took a look with my 3.8V Ryobi inspection camera before we committed to drilling all the way through. It fits into a 1/2" hole and has prevented a few surprises in the past.

 

[branimal]

I got the extension welded up - with the hole saw its about 72" long.

I have to stand on a ladder on the floor below and try to drill straight into the blocking. I can't even get the pilot bit started on the blocking. It's hard to get the extension plumb in both directions. So even if i get a hole drilled, it might not end up being in the correct spot.

I'll try again standing on a scaffold - after that I'll resort to cutting open the drywall. This technique would be great if it works - b/c I have to install 4 indoor mini split units on this floor.... that's 4 walls I won't have to patch and paint.

I do know where the wiring is b/c I ran it - and I can see it. There's a MC Cable about 20 inches off the finished floor. I did have a Rigid inspection camera - $80 version from a few years ago. I ended up going thru my stuff and selling things I haven't used in the last two years. Regretting that now.

 

[Muckin_Slusher]

Use a properly sized socket to go over the hex on the holesaw. Little tape will hold it on.

Then use whatever combo of 3/8 extensions required. From there you can drive it with a hex to 3/8 drive adapter.

Had to do this to get through rim joist and thick closed cell insulation. There's proper extensions available but for a 1 off this was perfect.

That sounds like a great way to loose your holesaw stuff in a wall cavity.

 

[PCustoms]

That sounds like a great way to loose your holesaw stuff in a wall cavity.

Fine, don't do it then.

 

[Muckin_Slusher]

Welding drill bits for extension works fine.

I've even welded Hilti SDS+ bits together, then drilled through concrete walls with them. I used 7018 then peened them as they cooled.

 

[branimal]

Ok, with the scaffold setup I was able to get my body square with the hole. Got it done.

Thanks for all the tips guys.

 

[Muckin_Slusher]

Fine, don't do it then.

Don't worry, I wont.
So there!

 

[The Cobbler]

There's a funny story attached to this set up. I might share it later . it's a long post but its in reference to this post from @Jim greengo

Not to derail this thread, and I already posted it here, here it is .

https://www.garagejournal.com/forum/threads/your-funniest-most-memorable-screw-up-on-the-job.436422/