Drill bit sizes for flexible conduit?

What're the typical size and type of drill bits for putting holes through framing to run flexible ENT conduit (aka smurf tube)?

I'll be running mostly 1" flex and a few 2". It's new construction and I'm, worst-case, going through no more than 6" of wood.

What's the right sizes? And which style will work best?

I'm assuming I'll need to purchase 2 each. I intend to avoid hitting any nails but I'd rather have a spare bit handy just in case (rather than wait for shipping).

Thanks!

Thanks, that clarifies things. The carlon website has a lot of literature, finding that one helps. I've got two different hole saw mandrels now, one Rigid and the other Milkwaukee, along with several hole saws.

I'm wondering whether picking up some large forstner bits might be worthwhile. Time saved on drilling the holes adds up. Clearing the chunks out of typical hole saws is a hassle, and not typically convenient to do while on top of a step ladder. Thus my thought of using a forstner or similar kind of bit comes to mind. Since it's new construction I'm not concerned about the added mess of wood shavings.

I've got 10' ceilings and 14" wide joist bays to contend with. I've got a Dewalt right-angle cordless and it's great for this sort of access. I've thankfully got several batteries and chargers and do expect to go through them. In the few places where I have better access and need more torque I'll use a corded drill. I've got a medium-sized one that should handle it.

Right, I've got both 1" and 2" flex conduit going in, along with a number of wires without conduit. I'm only putting the conduit in places where it'd really be advantageous to change later (like the outside walls that are getting spray foamed. But for some stuff it'll be just fine to run regular in-wall wire without the conduit.

Hard to decide whether to get the self-feed or auger kind (and then whether to spring for ones rated to handle nails).

Looks like I'll pick up a set of the regular auger kind, so I've got a few in-between sizes for the wire-only holes. Then probably a long 1/2" auger for a specific set of places that'll need it. I'll have to double-check the total thicknesses of areas that would have the 1" and 2" conduits going through. A few might have more than one 2x4 (king stud situations) so I'd certainly need either longer bit or an extension.

Sure, a hole saw is very likely to be faster than a spade bit, no question. At least not for framing material. Through something thin it wouldn't matter much either way. But I'm definitely dealing with all framing lumber, with some having 3/4" advantech subfloor (OSB, essentially).

The question is whether I should go with augers or the self-feeding kind. The latter being sort of a combination of a spade and a hole saw.

And yes, cheap hole saws are to be avoided.

I've ordered a couple of different bits. Both auger and self-feeding kinds. I'll report back what sort of performance I get out of them.

Yep, ordered a set of Irwin's 'weldtec' augers, along with two self-feeders and a hole saws. I also checked and local stores have similar bits in stock. I've learned over the years it's better to be over-equipped and get the job done, than under-equipped and have to waste time when things break.

It's new construction so I can see all sides of the wood and can probably avoid most nails.

There's one piece where the framers went a bit overboard with the nail gun, but I plan on removing that section and replacing it. It's the top plate of narrow bit of wall that was studded out in front of the exterior wall, specifically to provide a chase for 2" conduits. They just nailed the bejesus out of the top of it, for no apparent reason. Easier to cut the whole piece out with a sawzall (whose blades are MUCH cheaper) and replace it with one nailed more effectively. Better that than wrecking a bit and slowing the job.

One remaining question will be how well my existing corded drill will handle the bits and the wood. I ran a few tests with my 18v cordless dewalts and they're not quite up to the task. Yeah, they'll work but it'll take a lot longer than it would with a corded drill. I may end up renting a higher-end right-angle one just to be sure. But I'll get everything else drilled out first in order to maximize the rental time. I just don't see much need to own a $300+ right-angle beast of my own. I've got a cordless right-angle one that's good enough for 99.9% of the work I'm ever likely to perform. It's bad enough I had to shell out for a new 8' tall stepladder. The new house has 10' ceilings and my old 6' stepladder just wasn't high enough to do the job right.

Now I'm off to pick up some more 2" conduit...

Did a bunch of the holes this afternoon. Let me tell you, the money spent for the weldtec nail eating upgrade was WELL WORTH IT. First hole I have to drill hits a nail. Damn near too my arm off when it kicked back. But the bit survived and went on to cut at least another two dozen holes. This was the 3/4" ship auger size. I also picked up a 2-9/16" self-feeder and it likewise did a phenomenal job. Chewed through three 2x4s like butter. But it did tend to bind up quite suddenly if I wasn't careful about keeping it nearly dead-straight. It took nice big clean CHUNKS of wood out in the process. Had to use the open hose from the shop vac to clean up the mess from it. Whereas the ship augers cut much smaller pieces.

One observation though, a 2-9/16 isn't quite wide enough for the bell-end of 2" gray PVC conduit. Which is ok for my particular situation as I don't need to feed pieces that way.

My cordless 18v DeWalt handled the 3/4" ship augers just fine. But for a 1-3/8" auger and the 2-9/16" it just didn't have enough torque. Fortunately I brought along a corded 3.8a hammer drill and it worked great. But I did have three situations that I couldn't quite get in there tight enough. I will need to pickup a right-angle unit. Sunbelt rents then locally for $20/day. And I really don't have much long-term use for a corded right-angle drill.

That and there's definitely something to be said for extensions. There are a couple of places where the typical 17" bit is just too long. But a regular 6" one is too short. I'm going to pick up a shorter extension. I've got one corner where I could use the 6" bit if I had another 6" extension. They do sell 12" bits, and that would work too.

And you know this, how? By assuming? Don't.

I'm well acquainted with what is or isn't structural in a building. The area in question was a built out section specifically added to house the conduits. Not part of structure at all. More a matter of how the carpenters chose to frame it both above and below the subfloor. I've got the actual plans that lay out what is or isn't structural or load bearing, as approved by licensed engineers and the county.

I've already seen the Simpson literature as we've got their products used in quite a few locations in the house. Quite a nice variety of products. Their nail stops get added as we move along.

You make an excellent observation, thank you.