Self Tapping Screws to Steel 2

[Jerehmy]

A project is underway and I was told to look at the handrail connections way too late. Like its being built right now.

One of the connections has the handrail terminating at a 6" tube column and calls for a Hollander bracket to be bolted to the column. The detail doesn't show the bolts going all the way through and they don't want them to be bolted through. A bolt won't work here since nothing would stop it from pulling out.

I don't know much about self-tapping screws into steel other than cold form sections. I did a little research but can't find any 3/8" diameter stainless steel self tappers. Drill-Flex goes up to 5/16".

I don't know the tube column thickness, but they have very little load so its safe to assume they are 1/8" thick.

Is there any other type of screw/fastener that can make this connection other than bolting through?

Thanks.

 

[mike20793]

Self tapping screws should be okay for that thickness. Simpson has values for shear and tension, so you would only need to check pull out and pull over. If you're worried it might be too thick for self tapping screws, you could weld on a thinner angle and screw to that.

 

[azcats]

Hollo Bolt?

 

[KootK]

I'd wager a paycheck that 6" column has at least .25" thick walls. Should be doable either way.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Brad805]

For one or two bolts they can tap the column with NC threads. I have done this myself and it is not difficult.

 

[mike20793]

Good idea to use the Hollo Bolts. I always forget how useful those things are when connecting to HSS.

 

[Jerehmy]

Kootk - I'm gonna find out the thickness cause' I could use the extra cash hehe

I can't find 3/8" diameter self tapping steel screws.

I'm checking Hollo Bolts now. Thanks!

 

[Jerehmy]

Found a good article for future readers in my situation:

http://www.structuremag.org/?p=7611

 

[KootK]

Does that mean I get one of your paychecks if I'm right?!?

Depending on your location, consider the availability/lead time of the Hollow bolts. Rumor has it this stuff is being built as we type...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Jerehmy]

Haha yes, but you would likely be very disappointed

Yeah I noticed they are quite a bit away, started looking for wedge anchors for steel that are closer.

I mean I'd prefer self tapping stainless, but I can't seem to find 3/8" ones. I'm just going to call the contractor and see what he had in mind or what he has used in the past on HSS sections. I'm not in a big metropolitan area, so material selection is limited if you need it quick.

 

[KootK]

@Jeremy: I might have been disappointed 12 months ago. With the Canadian dollar as it is, I could probably live off of your UI contributions. Might have to jump stateside again if oil prices persist...

@Brad: I've always been shy about specifying tapping because I don't know much about it and I've been worried about cost. It's a relief to hear that it's not a big deal. Would you mind elaborating a bit regarding the equipment, skill sets, and man-hours required to do some localized tapping?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Brad805]

Koot, there is a sample tap set below. Basically one pre-drills a hole to the size suggested and then one can create the threads by hand. I have done so for holes up to 3/8" for projects at home in plate up to 1/2" thick. When doing them manually the first threads are not always perfect because you can get the angle off. 1/4" wall would be about as thin as I think practical for manual holes. Most steel guys have mag setups and they can make threads perfectly in the field. I have watched glaziers do this quite a few times for pretty arch standoffs. They always grumble and try for an extra, but it can solve a problem in a case like this. We hear complaints from the trades with self tapping screws once we go much beyond 0.060" wall thickness.

http://www.dx.com/p/wlxy-wl-6520-tap-and-die-set-20-pcs-269073#.VdToNvkuBhU

 

[msquared48]

What about welded threaded rod? Washers as needed...

Mike McCann, PE, SE (WA)

 

[BButler505]

Look at the Hilti website. I use their self drilling screws a lot, they have screws capable of making the connection. Shear and tension capacities are listed as well.

 

[RPMG]

You can use blind bolts or hollo-bolts. They might be overkill. I would "tap and die" screws, which is very simple and cheap. It can be time consuming if doing it in the field 100 times. You're not limited to self-tapping.

 

[KootK]

Oh. My. Gawd! According to Brad's link, we can have our very own tapping sets for $26. I'm going to have one Fedex'd to me and spend the weekend tapping everything I can get my hands on.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[RPMG]

They're also sold at home depot. You can start tomorrow.

 

[Ron]

Jehremy......

There are 3/8" self drilling screws out there....plenty of them. A couple of links.....


American Fastener

Fastenal

 

[Jerehmy]

Ron - I swear I looked, specifically at fastenal. Not sure how I missed them.

 

[Ron]

Jerehmy.....I know how it is. It's amazing sometimes how suppliers actually hide the things they are trying to sell, just because of poorly referenced website menus. For Fastenal, you have to search by category first, then drill down to diameter. They make you work for it!