[Apples]

Hi all,

I need to bolt a bit of flat steel to the top side of a length of box section.
How can I do this?

Because it is fully enclosed I can not get a nut inside. It is going to be about 4-5mm thickness in wall section, maybe I can drill out some holes and tap them? Will 4-5mm be enough steel for there to be enough grip if I tap the holes with threads?

Any ideas on what I can do?

Apples
Australia

[svenakela]

How long is it supposed to be and how many screws?
If it's not too long and have open ends, you can take a piece of 8-10 mm flat steel at equal length prepared with threaded holes that you stick through the box.
Is there any problem with drilling holes through the box and make the backside hole even bigger so you can put a nut in from the backside? Maybe you can have the nut on the outside and use Allen-screws from the inside of the box and out? In that case the backside hole must not be very oversized, just a little bit bigger.

[RICHARD ZASTROW]

Apples, If the flat steel is thick enogh, you could counterbore the back side of the flat and weld a nut (jam-type?) to the box section and bolt thru the flat steel. Just an idea.

[sanddrag]

put a hole on the opposite wall of the box tube that is big enough for whatever tool you are using (screwdriver, socket, allen wrench, etc) to get in there.

[massajamesb]

If you are tapping it to (I will refer to it in Imperial, as I am not real familiar with metric) say, 1/4" fine thread, then maybe. Anything much larger, and you will not have enough thread to make it happen.
My suggestions: center punch the initial hole, of course, drill it out to 1/4"
and then either:
1. Get a hole saw and some DOM tubing you can thread, and hole saw through the tubing, insert the threaded DOM, and weld up the DOM inside the box
or
2. Cut a hole with whatever size hole saw, and drill out the pilot hole to whatever size your bolt will be, on the circle piece you cut out. Weld a nut to this circle piece, put it back in place, get it exactly where you want it, and burn it back into place.
or
3. Drill all the way through the box, and just put the nut on the backside of the tube.
Not real sure what you are trying to do, so I don't know if any of this will work.

[Apples]

Well thanks for all the ideas. I think the simplest idea is to put a hole opposite the bolt. See below.

It is for a cnc rail.

Peter
Australia

[JOE65]

riv nuts
http://www.aircraftspruce.com/catalo...es/rivnuts.php

[ViperTX]

The problem with rivetnuts....is that they are not flush.....as someone mentioned....weld a jam nut, weld a stud..4 or 5 mm wall thickness...you can also drill and tap it.

[svenakela]

Well thanks for all the ideas. I think the simplest idea is to put a hole opposite the bolt. See below.

It is for a cnc rail.

Peter
Australia

As I wrote earlier, if you can mount the nut on the outside the opposite hole doesn't have to be a lot bigger if you use Allen-screws. That's how my table is done.

Regards,
Sven

[cozymkiv]

Use flow drilling Try http://www.robertspeck.com/formdt.htm

Hennie

Hi all,

I need to bolt a bit of flat steel to the top side of a length of box section.
How can I do this?

Because it is fully enclosed I can not get a nut inside. It is going to be about 4-5mm thickness in wall section, maybe I can drill out some holes and tap them? Will 4-5mm be enough steel for there to be enough grip if I tap the holes with threads?

Any ideas on what I can do?

Apples
Australia