Attaching plywood underlayment to metal channel

[Lee Schierer]

I need to attach some 3/4" underlayment plywood to some steel channels that are about 1/8-3/16" thick. I am considering using Teks self drilling screws (https://www.lowes.com/pd/Teks-10-x-1-7-16-in-Phillips-Drive-Sheet-Metal-Screws-100-Count/3316524). Has anyone used these screws for a similar application? Any useful tips for using them?

[Cameron Wood]

I've mostly used hex head drill point screws- similar. If they're hard to get in, drill pilot holes.

[Jerry Bruette]

I used a similar type screw to attach 2x6's to metal. Be sure the length of the drilling tip is longer than the thickness of the metal. Otherwise the threads will want to engage the metal frame before the hole is drilled all the way through.

I had to predrill all the holes for my project but the screws worked perfectly.

[Tom Bender]

As Jerry suggested, there could be problems. If you are in a hurry and don't want to predrill, you might save time.

[Tom M King]

I've used similar ones to fasten trailer 2x decking boards into similar thickness steel. They will/might work, but are much easier to drive, and work every time in a predrilled hole. A spade handled 1/2" drill works better than an impact driver if you don't predrill. I use an impact driver with predrilled holes.

[John K Jordan]

I need to attach some 3/4" underlayment plywood to some steel channels that are about 1/8-3/16" thick. I am considering using Teks self drilling screws (https://www.lowes.com/pd/Teks-10-x-1-7-16-in-Phillips-Drive-Sheet-Metal-Screws-100-Count/3316524). Has anyone used these screws for a similar application? Any useful tips for using them?

Will your fasteners go through the metal and into the wood or through the wood and into the metal?

I use self drilling screws a lot, great for cutting threads in the steel. (I didn’t check out the ones you linked to.) The drill point on such screws does not make a clearance hole so they are not much good for where the screw needs to go through the steel and into wood, good for the other direction but that leaves a point and maybe some threads sticking up into the channel.

If going through the steel and into the wood and if I wanted the inside of the channel unobstructed I’d drill clearance holes in the steel, countersink if appropriate, then drill pilot holes into the wood and fasten with wood screws. If the screws will go through the wood I’d drill almost clearance holes in the wood, countersink if appropriate, then use the right length of self drilling/tapping screws.

You can get very good screws from a trailer maker/dealer/repair shop. All of my big trailers and the horse trailers use torx flat-head screws through wood and into the steel support frame below, usually angle iron.

JKJ

[Tom M King]

I just noticed those were Phillips head. I would say to definitely find the TORX head ones. I bought some off Amazon a few months ago. Just search for trailer floor screws. They come in a lot of sizes.

edited to add: These are the ones I bought. I wouldn't count on 100% success with self-drilling, but easily 100% success in predrilled holes.

https://www.amazon.com/12x2-1-Reamer-Self-Drilling-Metal-Screws/dp/B07ZWCRNYK/ref=sr_1_6?crid=3OAKZFJ4D5EZF&keywords=trailer+floor+screws&nav_sdd=aps&qid=1669854049&refinements=p_n_feature_five_browse-bin%3A3177290011&rnid=3177270011&s=industrial&sprefix=trailer+floor+sc&sr=1-6