In your situation I would use 1 1/2 in screws with a hex head. Get a magnetic bit. I like the the self tapping part to not be pointy but look more like a drill bit. I ditch the washers - they are a rubber washer for metal roofing and I like metal on metal contact. I never predrill.

The drill works fine for tek screws; you can use it, too. The impact driver really excels at driving screws that require more torque, like deck screws into wood.

You'll want to get a set of deep well impact sockets for the driver; they'll be black. Regular chrome socket sets will work for a while, but the driver will eventually strip out the inside of the socket.

I figured driving screws into metal would require more torque than wood? Not too much more wood to screw together. I'm predrilling the wood (oak? surveyor's stakes for the corners & joining raised beds). Almost done with the first 60ft - later this week will do the other side of the tunnel but I need to buy more wood - running out of cypress. Can't get any more until we get the chicken coop out of the truck.

Too many projects going on right now (after planting out tomatoes & peppers have to build a run, if time before picking strawberries)!

When I put up my 26 by 72 this spring, the impact driver did a great job on removing the TEK screws and a great job with putting on and taking off all the bolts, but it was terrible at driving in new TEK screws. They just kept turning and turning, but wouldn't bite into the metal very fast. I reached over and grabbed my drill and the screw was in in a few seconds. Use the drill for the TEK screws, IMO.

A Tek screw is basically a single use drill bit and screw combo.

Jay

I had the same experience. The impact driver is overpowered for screws that small. When screwing into tough sheet metal, it will just strip out the inside of the bit. I figured out that the drill works better when I was working on an old rental trailer last fall, screwing the siding back down.

Anything larger than a tek screw or trailer sheet metal screw gets the impact driver, though, I love that thing. With the right sockets, it will take the tires off your car, or any farm equipment. It's great for breaking loose rusty old bolts.

Thanks - I will return the combo (haven't opened it yet) and look for a new drill. They had another combo (same price) with a 5.5" circular saw which may be more useful.

Still wondering what size tek screw is needed to bite into the galvanized steel hoops? Not length, but the "bit" part?

i can control the speed of the impact driver better than i can the drill. when i start the screw i go very slow so it doesn't skate and i can see it bite. mine is a ryobi.

I got the Ryobi. Not going to return it since DH reminded me we borrowed a cordless circular saw 10-15 years ago and it was underpowered (unless they've gotten more powerful). Tried the impact driver to drive 4" wood screws and the bit came out, he didn't have it chucked in tight I guess but the R driver has been doing well. Almost finished building the raised beds along east side of tunnel - need more stakes for the corners. He took today off from work to help me - 1st thing had to cut 4 2ft sections of cypress with a hand saw for the ends/dividers since I used 6 out of the first 8 he had cut for the west side. I thought boards were 16ft but they were 12ft (+/- 3"!)