Thread: Attach awning brackets to a Steel Hollow Section

Originally Posted by DJ's Timber

For example, a plate that matches your bracket then drill and tap both pad and column.

Now this idea I like.


shedhappens The stuff I was reading said formulas dont work very well for this sort of thing as the first turn of thread holds over 1/3 of the load, each thread after that holding less and less.
http://www.elexp.com/tips/AllAboutScrews.pdf page 16.

Stuart

The awning weighs only 80KG so it is by no means heavy, (in structural terms). To be quite honest I have no idea why 12mm bolts are being used, 8mm bolts would easily hold the weight.
I would have no concerns at all tapping holes in 5mm steel to take M8, M10 or M12 bolts, just ensure that you have a good hole, undersized rather than oversized and use a good cutting lubricant so as to cut a good quality thread. In the case of M12, metric fine would possess some advantages over course, but I wouldn't get too bent out of shape worrying about it. For that matter heavy gauge TEK screws would have adequate strength.

Originally Posted by Karl Robbers

The awning weighs only 80KG so it is by no means heavy, (in structural terms). To be quite honest I have no idea why 12mm bolts are being used, 8mm bolts would easily hold the weight.

Wind loads perhaps?

Edit: Wind can generate a lot of force. I've seen a shade sail pull down a besser brick garage wall. It wasn't a big sail and I don't recall it being excessively windy either.

Maybe attach awning to thickish plates that can have the nut countersunk, or tap the plates themselves for the M12 bolts, then attach plates and awning to posts with a series of smaller bolts, such as M8?

Nev

I just wanted to provide you all with an update on my decision/approach.

Firstly I think the best approach offered, and probably the more professional one, is welding a plate on the the existing steel section. But I don't have a welder or any spare metal.

The thread approach, as suggested by many tapping a tread in the steel section may have also be adequate, but I was reluctant as I would need to purchase a tap and die set. This solution also didn't offer me the piece of mind I would need to sleep better at night.

In the end I decided to just drill a 25mm hole, with a hole saw, in the middle and pass the bolts into the steel section and out through the holes. Could have done it with a 22mm but they didn't have one in stock. BTW, the steel section is around 150mm wide.
It was a lot easier than I expected. The hole saw cut through the steel much easier than the 12mm bit I used for the bolt hole.

Threading the bolts though the holes was quite easy too. I used braided fishing line and some spring wire. Spring wire to hold the bold horizontal while inside the steel section, and braided fishing line to pull it through the hole.

Also, I was able to better measure the thickness of the steel section with vernier calipers once I removed the piece out of the hole saw. It was 6mm thick.

Thanks

John