T i m wrote:
On Sun, 13 May 2018 12:42:15 +0100, "Dave Plowman (News)"
wrote:

In article ,
T i m wrote:
I'm probably looking at M8/10 machine screw sizes going into ~3mm
rolled steel box and angle iron, I'd be using steel Rivet Nuts (I'm
not sure stainless Rivet Nuts would be ideal into mild steel?) and
only need 10's, not 100's etc.

I've used them a lot. Although generally smaller sizes.

Would you think that in a worst case situation (tension) they would
offer as much strength / pull-though resistance as a conventional hex
nut Dave? I was thinking a nut would offer a greater surface area but
maybe the bolt or it's thread would fail first in any case?

Should we use the special tool (again, production speeds aren't an
issue here) or can a simple bolt and back nut and a thrust bearing or
some washers provide the same effect?

A decent tool is IMHO essential for setting them correctly. And make sure
spares are available for it.

Understood. That may be on my wish list though, depending on the
price.

I use M3 quite a bit and it is tricky to get exactly the right setting
without snapping off the arbor on such a small size.

Understood.

Needs to be a very
high quality steel used to pull it tight - a normal bolt will likely not
be strong enough. And turning a bolt rather than pulling on it more likely
to damage the thread.

You don't turn the bolt in the riv nut you screw a nut down on a rod
threaded into the riv nut if you do not have professional tools and that
is perfectly satisfactory although time consuming and you can put a
thrust race under the nut if you have one.

Ok.

So saying, larger sizes seem easier.

I think I would use the 'backnut' process where the bolt thread stays
still in the rivet nut and the rivet nut just drawn in without the
thread turning. I might also turn up a 'tool' to ensure they are held
in firmly and square etc.

I'd guess a tool which automatically produces the correct 'pull' for any
given size ain't going to be cheap.

My fear also ... and I'm not sure would be justified in this scenario
and for these quantities.

Most of the lower priced ones rely on
you providing the correct force. Although can be set to a limit. If you
are doing lots into the same material, you could experiment for the best
settings on some offcuts. And keep those settings.

Understood. I have several torque wrenches. ;-)

Given you don't need access to the back (to hold a nut) then I was
thinking I could use more of these than I might with a conventional
nut and bolt, think riveting up a ships hull plate versus fixing an
air vent into place etc. ;-)

Cheers, T i m